FEMA Guide to RetrofittingHomeowner’s Guide
to Retrofitting
Six Ways to Protect Your Home From Flooding
FEMA P-312, 3rd Edition / June 2014
Homeowner’s Guide
to Retrofitting
Six Ways to Protect Your Home From Flooding
FEMA P-312, 3rd Edition / June 2014
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING i
Preface
The Federal Emergency Management Agency (FEMA) has prepared this guide specifically for homeowners who
want to know how to help protect their homes from flooding. As a homeowner, you need clear information about
the options available to you and straightforward guidance that will help you make decisions. This guide gives you
both, in a form designed for readers who have little or no experience with flood protection methods or building
construction techniques.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING iii
Acknowledgments
Third Edition Authors and Key Contributors
Seth Frost-Tift, URS Group, Inc.
Amit Mahadevia, URS Group, Inc.
Deborah Mills, Dewberry
Adam Reeder, Atkins
Adrienne Sheldon, URS Group, Inc.
John Squerciati, Dewberry
Third Edition Reviewers and Contributors
Daniel Bass, FEMA Headquarters
William Coulbourne, URS Group, Inc.
Franki Coons, FEMA Headquarters
Jhun de la Cruz, FEMA Headquarters
John Grace, FEMA Region I
Karolyn Kiss, FEMA Headquarters
John Ingargiola, FEMA Headquarters
John “Bud” Plisich, FEMA Region IV
Steven VanDyke, FEMA Headquarters
Gregory Wilson, FEMA Headquarters
Wallace Wilson, URS Group, Inc.
Third Edition Technical Editing, Layout, and Illustration
Young Cho, URS Group, Inc.
Julie Liptak, Stantec
Lee-Ann Lyons, URS Group, Inc.
Susan Patton, URS Group, Inc.
Ivy Porpotage, URS Group, Inc.
Billy Ruppert, URS Group, Inc.
Amy Siegel, URS Group, Inc.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING v
Table of Contents
Preface ..................................................................................................................................................i
Acknowledgments ..............................................................................................................................iii
Acronyms .........................................................................................................................................xiii
1.0 About this Guide .....................................................................................................................1-1
1.1 Who This Guide Is For .....................................................................................................................1-1
1.2 How This Guide Can Help You .........................................................................................................1-2
1.3 How To Use This Guide ...................................................................................................................1-2
2.0 Introduction to Retrofitting .....................................................................................................2-1
2.1 What Is Retrofitting? .......................................................................................................................2-3
2.2 Types of Flooding ............................................................................................................................2-3
2.3 How Flooding Can Damage Your Home ..........................................................................................2-5
2.3.1 Depth/Elevation of Flooding..............................................................................................2-5
2.3.2 Flow Velocity ......................................................................................................................2-8
2.3.3 Flood Frequency ................................................................................................................2-9
2.3.4 Rates of Rise and Fall ........................................................................................................2-10
2.3.5 Duration ...........................................................................................................................2-11
2.3.6 Debris Impact ...................................................................................................................2-11
2.4 Other Hazards ...............................................................................................................................2-11
2.5 Federal, State, and Local Regulations .............................................................................................2-12
2.5.1 The Community Rating System ........................................................................................2-13
2.5.2 Flood Insurance Rate Maps...............................................................................................2-14
2.6 Financial Assistance for Retrofitting ...............................................................................................2-16
2.6.1 Federal Programs..............................................................................................................2-16
2.6.2 Non-Federal Help ............................................................................................................2-20
vi SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
TABLE OF CONTENTS
3.0 An Overview of the Retrofitting Methods ................................................................................3-1
3.1 Cautions ..........................................................................................................................................3-2
3.1.1 Substantial Improvement / Substantial Damage .................................................................3-2
3.1.2 Basements ..........................................................................................................................3-3
3.1.3 Flood Protection Elevation and Risk ...................................................................................3-3
3.1.4 Freeboard and Flood Mapping Uncertainties .....................................................................3-6
3.1.5 Human Intervention ..........................................................................................................3-8
3.1.6 Other Considerations .........................................................................................................3-9
3.2 Construction Terminology .............................................................................................................3-10
3.2.1 Construction Type ............................................................................................................3-10
3.2.2 Foundation Type ...............................................................................................................3-11
3.3 Retrofitting Methods and Costs .....................................................................................................3-12
3.3.1 Elevation ..........................................................................................................................3-12
3.3.2 Relocation and Demolition ..............................................................................................3-20
3.4 Floodproofing ...............................................................................................................................3-25
3.4.1 Wet Floodproofing ...........................................................................................................3-25
3.4.2 Dry Floodproofing ...........................................................................................................3-28
3.4.3 Barrier Systems ................................................................................................................3-31
3.5 Summary .......................................................................................................................................3-36
4.0 Deciding Which Method Is Right for Your Home .....................................................................4-1
4.1 Making Your Decision ......................................................................................................................4-2
4.1.1 Step 1 – Determine the Hazards to Your Home ..................................................................4-2
4.1.2 Step 2 – Inspect Your Home ...............................................................................................4-3
4.1.3 Step 3 – Check with Your Local Officials ..........................................................................4-11
4.1.4 Step 4 – Consult a Design Professional and Retrofitting Contractor ................................4-12
4.2 Decision-Making Matrices .............................................................................................................4-15
4.2.1 Evaluation Factors ............................................................................................................4-15
4.2.2 Substantial Improvement / Substantial Damage Matrix ....................................................4-17
4.2.3 NOT Substantial Improvement / NOT Substantial Damage Matrix ..................................4-18
5.0 Elevating Your Home ................................................................................................................5-1
5.1 Considerations .................................................................................................................................5-2
5.1.1 Amount of Elevation ..........................................................................................................5-2
5.1.2 Existing Foundation ...........................................................................................................5-4
5.1.3 Hazards ..............................................................................................................................5-5
5.1.4 Access ................................................................................................................................5-5
5.1.5 Home Size, Design, and Shape ...........................................................................................5-6
5.1.6 Service Equipment .............................................................................................................5-6
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING vii
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5.2 The Elevation Techniques .................................................................................................................5-6
5.2.1 Elevating on Extended Foundation Walls ............................................................................5-6
5.2.2 Alternative Elevation Techniques for Masonry Homes on Slab-on-Grade Foundations .....5-15
5.2.3 Elevating on an Open Foundation ....................................................................................5-20
6.0 Relocation and Demolition ......................................................................................................6-1
6.1 Relocation .......................................................................................................................................6-1
6.1.1 Considerations ...................................................................................................................6-2
6.1.2 The Relocation Process .......................................................................................................6-3
6.2 Demolition ......................................................................................................................................6-9
6.2.1 Considerations .................................................................................................................6-10
6.2.2 The Demolition Process ...................................................................................................6-11
7.0 Floodproofing ..........................................................................................................................7-1
7.1 Wet Floodproofing ..........................................................................................................................7-1
7.1.1 Design Flood Elevation .......................................................................................................7-2
7.1.2 Hazards ..............................................................................................................................7-2
7.1.3 Post-Flood Cleanup ............................................................................................................7-3
7.1.4 Modifications Required for Wet Floodproofing ..................................................................7-5
7.1.5 Installing Openings ............................................................................................................7-5
7.1.6 Protecting the Underside of Elevated Buildings ..................................................................7-7
7.1.7 Using Flood Damage-Resistant Materials ...........................................................................7-8
7.1.8 Protecting Service Equipment ............................................................................................7-9
7.2 Dry Floodproofing ...........................................................................................................................7-9
7.2.1 Considerations .................................................................................................................7-10
7.2.2 Modifications Required for Dry Floodproofing ................................................................7-12
8.0 Barriers ....................................................................................................................................8-1
8.1 Levees ..............................................................................................................................................8-2
8.2 Floodwalls .......................................................................................................................................8-3
8.3 Temporary Barriers ..........................................................................................................................8-3
8.4 Technical Considerations .................................................................................................................8-4
8.4.1 Height of Barrier ................................................................................................................8-4
8.4.2 Basement Foundations .......................................................................................................8-5
8.4.3 Soil Conditions ...................................................................................................................8-5
8.4.4 Duration of Flooding .........................................................................................................8-5
8.5 Additional Considerations ...............................................................................................................8-6
8.5.1 Annual Maintenance ..........................................................................................................8-6
8.5.2 Housing of Occupants .......................................................................................................8-6
8.5.3 Access to Structure .............................................................................................................8-6
viii SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
TABLE OF CONTENTS
8.5.4 Human Intervention ..........................................................................................................8-6
8.5.5 Interior Drainage ................................................................................................................8-7
9.0 Protecting Service Equipment ..................................................................................................9-1
9.1 Elevation ..........................................................................................................................................9-2
9.1.1 Maintaining Horizontal and Vertical Clearances .................................................................9-4
9.1.2 Venting Considerations ......................................................................................................9-5
9.1.3 Unions, Fittings, and Valves ................................................................................................9-5
9.2 Relocation .......................................................................................................................................9-5
9.2.1 Electrical Panels ..................................................................................................................9-5
9.2.2 Electric Meters ....................................................................................................................9-6
9.2.3 Electrical Wiring.................................................................................................................9-6
9.2.4 Mechanical Systems ...........................................................................................................9-6
9.2.5 Water Heaters .....................................................................................................................9-7
9.2.6 Washer/Dryer Units ...........................................................................................................9-7
9.3 Protection in Place ...........................................................................................................................9-7
9.3.1 Floodwalls and Shields .......................................................................................................9-8
9.3.2 Anchors and Tiedowns .......................................................................................................9-8
9.3.3 Backflow Valves ................................................................................................................9-10
Appendices
Appendix A Bibliography and Sources of Information
Appendix B Glossary
Appendix C FEMA Regional Offices
Appendix D NFIP State Coordinating Agencies
Appendix E State Historic Preservation Offices
Appendix F Professional Organizations
Appendix G Retrofitting Checklist
Figures
Figure 2-1. This home in New Orleans was inundated by 4 feet of water during Hurricane Katrina. ............2-1
Figure 2-2. This home, from Figure 2-1, was elevated in a manner that added to both its appearance and
its value. As a result of its elevation, the home avoided major damage from Hurricane Isaac
in 2012. .......................................................................................................................................2-2
Figure 2-3. These homes in Gays Mills, WI, were inundated by riverine flooding during the Midwest
floods of 2008. .............................................................................................................................2-4
Figure 2-4. The extreme impact of large, fast-moving waves, combined with the removal of supporting soil
by erosion and scour, can have devastating effects on buildings exposed to coastal flooding.
Hurricane Floyd destroyed this home along the coast of North Carolina in 1999. ......................2-4
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING ix
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Figure 2-5. In this example, the 1-percent-annual-chance flood elevation is 391.6 feet (10.1 feet above the
benchmark elevation of 381.5 feet), and the elevation of the lowest floor of the home is 389.3
feet (7.8 feet above the same benchmark). The flood depth above the lowest floor is therefore
equal to 391.6 feet − 389.3 feet, or 2.3 feet during the 1-percent-annual-chance flood. ............2-6
Figure 2-6. Hydrostatic pressure acts on walls and concrete slab floors. The weight of saturated soils adds
to the pressure on basement walls. Figure 2-6a shows a home with a concrete slab floor. Figure
2-6b shows a home with a basement. ..........................................................................................2-7
Figure 2-7. The walls of this basement in Wisconsin failed because of the pressure exerted by water and
saturated soil. ...............................................................................................................................2-7
Figure 2-8. Once water enters the home, hydrostatic pressure is equalized. Figure 2-8a shows a home
with a concrete slab floor. Figure 2-8b shows a home with a basement. ......................................2-8
Figure 2-9. Moving water acts on the front, sides, and back of a home. .........................................................2-9
Figure 2-10. Water moving at high velocity destroyed the wall of this home and caused the building to
shift on its foundation. .................................................................................................................2-9
Figure 2-11. Wind forces on a sealed building are less than wind forces on a building with an opening. .....2-12
Figure 2-12. Earthquake forces act in both horizontal and vertical directions.................................................2-12
Figure 2-13. This FIRM for riverine flooding shows the SFHA (Zone AE), floodway (hatch-marked Zone AE
along centerline of river channel), and areas outside the SFHA (Zone X). The area between the
limits of the base flood and 0.2-percent-annual-chance flood are delineated by shaded Zone X.
Areas above the 0.2-percent-annual-chance flood are delineated by unshaded Zone X. .............2-15
Figure 3-1. This graph shows the relationship between flood recurrence intervals and the probability of an
event occurring within a 30-year period......................................................................................3-6
Figure 3-2. Portion of a paper FIRM showing coastal flood insurance rate zones. The icons on the right
indicate the associated flood hazard zones for design and construction purposes. The LiMWA
is not shown on older FIRMs, but is shown on newer FIRMs. ......................................................3-7
Figure 3-3. Typical transect perpendicular to the shoreline showing the delineations between Zone V, the
MoWA area, the LiMWA, Zone A, and the MiWA area. .................................................................3-8
Figure 3-4. Ty pical cross-sections of three common construction types: frame, masonry veneer, and
masonry. The foundation shown here for all three construction types consists of concrete
blocks and a concrete footing. The same construction types are also found on basement and
slab-on-grade foundations. .........................................................................................................3-11
Figure 3-5. Home foundation types. .............................................................................................................3-12
Figure 3-6. Typical cross-section of home elevated on continuous foundation walls. ...................................3-14
Figure 3-7. Before (left) and after (right) photos of a retrofitted home elevated on extended continuous
foundation walls. ........................................................................................................................3-14
Figure 3-8. Home elevated on reinforced concrete piers. .............................................................................3-15
Figure 3-9. Home elevated on posts .............................................................................................................3-16
Figure 3-10. Home elevated on piles. .............................................................................................................3-17
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Figure 3-11. Example of well-elevated and embedded pile foundation tested by Hurricane Katrina.
Note adjacent building failures (Dauphin Island, AL, 2005). .....................................................3-17
Figure 3-12. The owner of this flood-prone home in south Florida decided to build a new wood-framed
second story on top of the masonry first story. The new second story is well above the BFE. .....3-18
Figure 3-13. Many homes in the Town of Prattsville, NY, were slated for demolition during the recovery
effort following Hurricane Irene. ...............................................................................................3-23
Figure 3-14. A home with a wet floodproofed subgrade basement. ...............................................................3-26
Figure 3-15. A home with a wet floodproofed enclosure. ..............................................................................3-27
Figure 3-16. A typical dry floodproofed home. ..............................................................................................3-30
Figure 3-17. A home protected by a levee (left) and a floodwall (right). .......................................................3-33
Figure 3-18. A home protected by a levee. .....................................................................................................3-33
Figure 3-19. A home protected by a floodwall designed as a landscaping feature. ..........................................3-36
Figure 3-20. Example of floodwall and levee dimensions. ..............................................................................3-37
Figure 4-1. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings
and Other Structures, ASCE/SEI 7-10. Used with permission from ASCE. ....................................4-4
Figure 4-2. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II
structures located on sites with average alluvial soil conditions....................................................4-6
Figure 4-3. Difference between flood level and lowest floor in homes on crawlspace and basement
foundations. ...............................................................................................................................4-10
Figure 5-1. As shown in the cutaway view, the lowest floor is above the flood level. When at least 1 foot
of freeboard is provided, only the foundation is exposed to flooding. .........................................5-3
Figure 5-2. This home in Cedar Falls, IA, was elevated one full story. The garage and storage area are at the
home’s original elevation. ............................................................................................................5-4
Figure 5-3. With attention to detail and planning, homeowners have created attractive retrofitted homes. ....5-5
Figure 5-4a through 5-4d. Elevating a basement or crawlspace foundation home on extended foundation
walls. ............................................................................................................................................5-8
Figure 5-5. Cross-section view of slab-on-grade foundation variations. .......................................................5-10
Figure 5-6. Building a new foundation for a slab-on-grade home. ...............................................................5-11
Figure 5-7. Elevating a slab-on-grade home without the slab. ......................................................................5-11
Figure 5-8. House in Zone A was detached from its slab foundation (which remains) and elevated on
masonry piers. The floor system is supported by new wood joists (Mandeville, LA). .................5-12
Figure 5-9a through 5-9d. Elevating a slab-on-grade home with the slab attached. ........................................5-13
Figure 5-10a through 5-10c. Elevating by extending the walls of a solid masonry home. ...............................5-16
Figure 5-11. Elevation of the floor levels in a row house to maximize living area above the BFE in Zone A. ..5-18
Figure 5-12a through 5-12c. Home elevated by adding a new second story over an abandoned lowest floor. 5-18
Figure 5-13a through 5-13d. Elevating a basement or crawlspace foundation home on piers. ........................5-21
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING xi
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Figure 5-14. Home elevated on post or column foundations. .........................................................................5-22
Figure 5-15. Home elevated on piles. .............................................................................................................5-23
Figure 6-1. New foundation is being prepared. ..............................................................................................6-4
Figure 6-2. Clearing pathways beneath the structure for lifting supports. ......................................................6-5
Figure 6-3. Pathways for lifting beams. ...........................................................................................................6-6
Figure 6-4. Beams supported by cribbing are placed at critical lift points. .....................................................6-6
Figure 6-5. Hydraulic jacks lift the structure, and the home is separated from existing foundation. ..............6-7
Figure 6-6. Trailer wheel sets are placed beneath the lifting beams. ...............................................................6-7
Figure 6-7. The move to the new site begins. .................................................................................................6-8
Figure 6-8. House is lowered and connected to the foundation after the foundation is fully constructed. .....6-8
Figure 6-9. Typical mitigation reconstruction project. ..................................................................................6-12
Figure 7-1. Typical wet floodproofing. ............................................................................................................7-3
Figure 7-2. Wall openings must allow floodwaters not only to enter the home, but also to rise and fall
at the same rate as floodwaters outside the home. ........................................................................7-6
Figure 7-3. Sketch of foundation plan of home with multiple enclosed areas, each with flood openings.
Typical enclosures with flood openings (Left). Flood opening in typical crawlspace foundation
(Right). ........................................................................................................................................7-6
Figure 7-4. The lateral and buoyancy force resulting from the same depth of flooding is much less on a
home without a basement (a) than on a home with a basement (b). The pressure on basement
walls is caused by water and saturated soils. ...............................................................................7-11
Figure 7-5. Example of an exterior application of a spray-applied asphalt membrane (left) and an interior
application of a fiber reinforced polymer wrap (right). .............................................................7-13
Figure 7-6. A way to seal an existing brick-faced wall is to add an additional layer of brick with a seal in
between. Please note that weep holes (drainage) and wick drains are moved up to prevent
moisture from getting inside the walls. ......................................................................................7-13
Figure 7-7. In the “wrapped home” method, the lower portion of the home is protected with a temporary
layer of polyethylene film. As shown, a temporary drainage line is also required. ......................7-14
Figure 7-8. Heavy-gauge metal shield over sliding glass door opening. .......................................................7-16
Figure 7-9. Light-gauge metal shield held in place by permanently installed tracks. ....................................7-16
Figure 7-10. Low window raised approximately 2 feet and original opening filled with brick. .....................7-17
Figure 7-11. Drainage system for a dry floodproofed home. ..........................................................................7-18
Figure 8-1. Structure protected by levee (on left) and floodwall (on right). ..................................................8-1
Figure 8-2. Levee construction........................................................................................................................8-2
Figure 8-3. Structure protected by a floodwall with decorative stone finish. ..................................................8-3
Figure 8-4. Two-foot-high water-filled temporary barrier protecting a residence from flooding.. .................8-4
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Figure 8-5. The City of Boulder, CO, installed a “pop up” closure to this floodwall at a City office building
subject to flash floods. The closure floats up into place automatically when the site is flooded. ...8-7
Figure 8-6. Small patio floodwall with sump pump. .......................................................................................8-7
Figure 9-1. Air conditioning/heat pump compressor mounted on a brick pedestal outside an elevated
home. ...........................................................................................................................................9-3
Figure 9-2. Air conditioning/heat pump compressor mounted on a cantilevered platform attached to a
home elevated on an open foundation. ........................................................................................9-3
Figure 9-3. Water heater and furnace protected by a concrete floodwall with opening and gasketed
shield. ...........................................................................................................................................9-8
Figure 9-4. Anchoring a fuel storage tank with a concrete slab.......................................................................9-9
Figure 9-5. Example of an exterior backflow valve installed in a valve pit. ...................................................9-10
Tables
Table 2-1. Eligible Retrofit Activities by Program ........................................................................................2-19
Table 3-1. Advantages and Disadvantages of Elevation ................................................................................3-19
Table 3-2. Relative Costs of Elevating a Home .............................................................................................3-20
Table 3-3. Advantages and Disadvantages of Relocation ..............................................................................3-22
Table 3-4. Relative Costs of Relocation .......................................................................................................3-22
Table 3-5. Relative Costs of Demolition and Rebuilding .............................................................................3-24
Table 3-6. Advantages and Disadvantages of Wet Floodproofing .................................................................3-28
Table 3-7. Relative Costs of Wet Floodproofing ...........................................................................................3-29
Table 3-8. Advantages and Disadvantages of Dry Floodproofing .................................................................3-31
Table 3-9. Relative Costs of Dry Floodproofing ...........................................................................................3-32
Table 3-10. Advantages and Disadvantages of Levees and Floodwalls ............................................................3-35
Table 3-11. Relative Costs of Levees and Floodwalls .....................................................................................3-36
Table 3-12. Relative Costs of Various Retrofit Measures .................................................................................3-38
Table 4-1. Requirements for Design Professional and Contractor Services ..................................................4-13
Table 4-2. Retrofitting Methods for Substantially Improved or Substantially Damaged Homes ...................4-17
Table 4-3. Retrofitting Methods for Homes That are NOT Substantially Improved or Damaged ..................4-18
Table 7-1. Flood Damage-Resistant Materials ................................................................................................7-9
Table 8-1. Considerations for Using Barriers ................................................................................................8-2
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING xiii
Acronyms
ASCE American Society of Civil Engineers
ASFPM Association of State Floodplain Managers
AST aboveground storage tank
BFE base flood elevation
CDC Centers for Disease Control
CMU concrete masonry unit
CRS Community Rating System
DFE design flood elevation
DHS U.S. Department of Homeland Security
DRC Disaster Recovery Center
FEMA Federal Emergency Management Agency
FIRM Flood Insurance Rate Map
FIS Flood Insurance Study
FMA Flood Mitigation Assistance
fps feet per second
HMA Hazard Mitigation Assistance
HMGP Hazard Mitigation Grant Program
HUD U.S. Department of Housing and Urban Development
HVAC heating, ventilation, and air conditioning
IBC International Building Code
ICC Increased Cost of Compliance
IEBC International Existing Building Code
IRC International Residential Code
xiv SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
ACRONYMS
LAG lowest adjacent grade
LiMWA limit of moderate wave action
LOMA Letter of Map Amendment
MEP mechanical, electrical, and plumbing
MiWA Minimal Wave Action
MoWA Moderate Wave Action
mph miles per hour
MSC Map Service Center
msl mean sea level
NAVD North American Vertical Datum
NFIA National Flood Insurance Act
NFIP National Flood Insurance Program
NGVD National Geodetic Vertical Datum
NRCS National Resources Conservation Service
OSHA Occupational Safety and Health Administration
OSB oriented-strand board
PDM Pre-Disaster Mitigation
PNP private non-profit
RFC Repetitive Flood Claims
SBA Small Business Administration
SFHA Special Flood Hazard Area
SFIP Standard Flood Insurance Policy
SHMO State Hazard Mitigation Officer
SHPO State Historic Preservation Office
SRL Severe Repetitive Loss
UL Underwriters Laboratories
USACE U. S. Army Corps of Engineers
U.S.C. United States Code
USDA U.S. Department of Agriculture
UST underground storage tank
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 1-1
1.0 About This Guide
The Third Edition of FEMA P-312, Homeowner’s Guide to Retrofitting, has been prepared to update the state of art in
residential flood protection methods and reflect changes made to the National Flood Insurance Program (NFIP).
1.1 Who This Guide Is For
The Federal Emergency Management Agency (FEMA) has pre-
pared this guide specifically for homeowners who want to
protect their homes from flooding. It provides clear information
about the options available to you and straightforward guidance
that will help you make decisions. This guide is designed for
readers who have little or no experience with flood protection
methods or building construction techniques.
If you are an engineer, an architect, a construction contractor, or
someone with skills in those fields, you may want to ask FEMA
for copies of technical manuals that cover design and construc-
tion in greater detail. For example, all flood protection methods
described in this guide are discussed in depth in FEMA P-259,
Engineering Principles and Practices for Retrofitting Flood-Prone Residential
Structures, Third Edition (FEMA. 2012a). If you work in a coastal
area, FEMA P-55, Coastal Construction Manual: Principles and Practices of
Planning, Siting, Designing, Constructing, and Maintaining Residential Build-
ings in Coastal Areas, Fourth Edition (FEMA. 2011b), may also be useful. If you would like to obtain copies of these
documents or other FEMA documents referred to in this guide free of charge, you can download them from the
FEMA Web site (http://www.fema.gov/resource-document-library) or call the FEMA Publications Service Center
at 1-800-480-2520. See Appendix A for a list of documents concerning flood protection prepared by FEMA and
other agencies and organizations.
In addition to FEMA publications, architects and engineers may want to obtain literature from the American So-
ciety of Civil Engineers (ASCE). ASCE 24, Flood Resistant Design and Construction provides minimum requirements for
flood-resistant design and construction of structures located in flood hazard areas. ASCE 7, Minimum Design Loads for
Buildings and Other Structures, may also be useful since formulas for flood loads are described in this document.
DEFINITION
FEMA is an agency within the
Department of Homeland Security
(DHS) that administers the NFIP. The
NFIP is a Federal program, created by
Congress in 1968. The NFIP makes
flood insurance available to communi-
ties that adopt and enforce floodplain
management ordinance, regulation,
or provisions of the building code that
meet the minimum requirements of
the NFIP regulations.
1-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
1 ABOUT THIS GUIDE
1.2 How This Guide Can Help You
You should take steps to protect your home if it has been dam-
aged by flooding or is in an area where flooding is likely to
occur. But first, you need to know what methods are available,
how they work, how much they may cost, and whether they
will meet your specific needs. This guide covers all of those is-
sues. It also explains flood hazards and how they can damage
your home.
Flooding is only one of several natural hazards that may threaten
your home. This guide includes maps that will help you deter-
mine whether your home is in an area where earthquakes or
high winds occur, and it also explains when your retrofitting
project should include protection against these hazards.
Your state and local governments probably have adopted build-
ing codes and other rules and regulations that you will need to
know about. This guide explains how your local officials can
advise you on those codes, rules, and regulations. Regardless
of the flood protection method you choose, you may wish to
consult with a licensed architect, engineer, or contractor for assistance with some of the retrofitting measures
described in this guide. This guide describes the types of services you can expect design professionals and con-
tractors to provide.
1.3 How To Use This Guide
To get the most from this guide, you should first read Chapters 2, 3, and 4. Chapter 2 explains retrofitting and, by
describing how flood, wind, and earthquake forces can damage your home, helps you understand how retrofitting
works. Chapter 2 also provides a discussion of Federal, State, and local financial assistance programs that may help
pay for your retrofitting project. Chapter 3 provides short descriptions of the six flood protection methods covered
by this guide. It gives you the information you will need as you begin to think about how to protect your home,
including the approximate costs, advantages, and disadvantages of each method. Chapter 4 leads you through four
steps that will help you decide which method or methods will best meet your needs. Chapter 4 also explains how
to work with local officials, design professionals, and contractors.
When you finish Chapter 4, you will be ready to focus on a specific retrofitting strategy. In some cases, a single
method may adequately address your needs. In other cases, a combination of methods may be best. Then you can
move to Chapter 5, 6, 7, 8, or 9, depending on the method or methods you’ve chosen. Those chapters describe the
methods in greater detail and include photographs and illustrations that show how the methods are applied. Chap-
ter 9 explains how you can protect service equipment (utility systems; heating, ventilating, and air conditioning
[HVAC] systems; and large appliances) in conjunction with the retrofitting method you have chosen.
As you read this guide, you will often find information in the margins of pages—definitions (such as the one on
the previous page), notes, and warnings. Each is identified by a special symbol:
DEFINITION – The meaning of a technical or other special term. Where a term is first used in the
text, it is shown in bold type and the definition is provided in the margin. You can also find these and
other definitions in Appendix B.
DEFINITION
In this guide, the term local offi-
cials refers to the employees of your
community who are responsible for
floodplain management, zoning, per-
mitting, building code enforcement,
and building inspection. The responsi-
bilities of local officials vary from one
community to the next. In your com-
munity, you may need to work with
one or more of the following: flood-
plain administrator, building official,
city engineer, and planning and zon-
ing administrator.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 1-3
ABOUT THIS GUIDE 1
NOTE – Supplemental information you may find helpful, including things to consider as you plan
your retrofitting project, suggestions that can make the retrofitting process easier, and the titles and
sources of other publications related to flood protection and retrofitting.
CROSS REFERENCE – Reference to another relevant part of the text or another source of information.
WARNING – Critical information that will help you avoid mistakes that could result in dangerous
conditions, violations of your community’s ordinances or regulations, and possibly delays and high-
er costs in your retrofitting project. Be sure to read these warnings. If you are unsure about what a
specific warning means or what to do to avoid the problem it describes, consult your local officials.
Chapter 4 provides information about working with local officials.
A final note before you begin Chapter 2: No guide or other
document of this type can anticipate every retrofitting situation
or every concern a homeowner may have about undertaking a
retrofitting project. If you have questions that this guide does
not answer, consult your local officials. Other resources include:
FEMA’s Building Science Helpline, a technical assistance hotline,
can be reached at 1-866-927-2104 (phone) or FEMA-Building-
sciencehelp@dhs.gov (email).
If FEMA has set up a Disaster Recovery Center (DRC) in your
area in response to a Presidential Declaration of a Major Disas-
ter, members of the DRC Mitigation staff can answer questions
and advise you on recovery strategies. Call the FEMA Helpline at
1-800-621-3362 for the location of a DRC in your area.
Appendix A of this guide lists helpful publications from FEMA and other organizations. The FEMA Web site,
http://www.fema.gov, has information about all of these resources and more.
Appendix C lists the staff members of the FEMA Regional Office for your State.
Appendix D identifies your State NFIP Coordinator and State Hazard Mitigation Officer (SHMO).
NOTE
Many government agencies, including
FEMA and non-profit organizations,
maintain sites on the Internet where
you can find information about flood-
ing, high winds, earthquakes, and
other hazards. Appendix A includes a
partial list of available sites at the time
this guide was prepared.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 2-1
2.0 Introduction to Retrofitting
Every year, flooding causes an average of over 90 percent of the disaster-related property damage in the United
States and accounts for an average of over 75 percent of all Presidential Disaster Declarations. In fact, between 2003
and 2013, the NFIP paid an average of over $3.5 billion a year in flood claims. In 2012, the year of Hurricane
Sandy, the NFIP paid over $8 billion in flood claims.
Although recent improvements in construction practices and regulations have made new homes less prone to
flood damage, many existing homes continue to be repetitively damaged by flooding. In fact, repetitive loss
records account for approximately 30 percent of all claim payments made in the history of the NFIP. Between
1978 and 2014, over 186,000 homes were flooded more than once. These homes alone accounted for approxi-
mately $15 billion in flood damages, subjecting the owners to a cycle of flooding and repairing.
The good news is that this cycle of repetitive flood damage can be broken. Homeowners across the country have
protected their homes from flooding using the techniques described in this guide. One example can be found in
New Orleans, where many residential neighborhoods were inundated by Hurricane Katrina in 2005 (Figures 2-1
and 2-2).
Figure 2-1. This home in
New Orleans was inundated
by 4 feet of water during
Hurricane Katrina.
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2 INTRODUCTION TO RETROFITTING
Figure 2-2. This home, from
Figure 2-1, was elevated in a
manner that added to both its
appearance and its value. As
a result of its elevation, the
home avoided major damage
from Hurricane Isaac in 2012.
One family decided to take action after their home flooded dur-
ing Hurricane Katrina. They hired a contractor to elevate their
home on concrete piers so that it would be above the level of
future, similar floods (Figure 2-2).
At the outset of the project, the homeowners were concerned
about how the home would look after it was elevated. But once
construction was complete, their concerns were alleviated.
Access to the front door is now provided by a well-designed
double staircase that also serves as an architectural focal point.
In addition to providing protection from future floods, elevating
the home created a space below that could be used for parking
and storage.
In other areas where flooding has caused repeated damage,
entire homes have been relocated outside the flood hazard area
or protected by floodwalls and levees designed as attractive
landscaping features. As you read this guide, you will see that it
is possible to protect your home from flooding while preserv-
ing or even enhancing its attractiveness and value.
NOTE
Any retrofitting project you undertake
must meet the legal requirements of
your community, including the flood-
plain management ordinances your
community adopted to participate
in the NFIP. By enforcing these ordi-
nances, your community helps reduce
future flood damages. As explained
later in this chapter, the ordinances
are based on the 1-percent-annual-
chance flood, also referred to as the
“base flood.” Remember this term; you
will encounter it many times as you
read this guide. For more information,
see Section 2.3.3.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 2-3
INTRODUCTION TO RETROFITTING 2
2.1 What Is Retrofitting?
You may be wondering, “What is retrofitting and why is it necessary?” Retrofitting is making changes to an exist-
ing building to protect it from flooding or other hazards, such as high winds and earthquakes. You have already
seen one example of retrofitting, and you’ll learn about more in the following chapters.
Construction technologies, including both methods and mate-
rials, continue to improve, as does our knowledge of hazards
and their effects on buildings. Many existing homes were built
when little was known about where and how often floods and
other hazardous events would occur or how buildings should
be protected. As a result, retrofitting has become a necessary and
important tool in hazard mitigation.
In addition to any retrofit completed on your home, updated
Flood Insurance Rate Maps (FIRMs) and new legislation may
have implications for your insurance premiums. Before making
any changes to your home, FEMA strongly recommends that
you discuss retrofit options with your insurance agent and work
closely with design professionals and State and local officials.
2.2 Types of Flooding
This guide focuses primarily on retrofitting for flood protection. If you decide to retrofit your home, you’ll need
to be aware of other potential hazards as well, such as high winds and earthquakes. They are discussed later, but
first you must understand flooding—where and how it occurs, the nature of the threat it poses, and how it can
affect your home.
Most of the flooding that occurs in the United States is either
riverine or coastal flooding, although flooding also occurs
around lakes and ponds, and in areas where storm drainage
systems are not adequate. Riverine flooding, as its name implies,
occurs when rivers and streams overflow their banks (Figure
2-3). Riverine floodwaters can move quite rapidly, as in a flash
flood, or very slowly, as they often do where the land is gently
sloping or flat. The primary causes of riverine flooding are rain-
fall and rapidly melting snow (and sometimes a combination
of both). Water from rain and rapidly melting snow eventually
finds its way into stream channels. When the amount of water
being carried by a stream exceeds the capacity of the stream
channel, it spreads out into the area along the stream, common-
ly referred to as the floodplain. Usually, the homes and other
buildings at greatest risk from riverine flooding are those near
the stream channel, where the depths and speed of floodwaters
are often greatest.
DEFINITION
Hazard mitigation is sustained ac-
tion taken to reduce or eliminate
long-term risk to people and property
from hazards such as floods, hurri-
canes, earthquakes, and fires.
DEFINITION
Flash flood: A flood caused by heavy
or excessive rainfall in a short period
of time, generally less than 6 hours. A
flash flood rises and falls very quickly
and is usually characterized by high
flow velocities.
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2 INTRODUCTION TO RETROFITTING
Figure 2-3. These homes
in Gays Mills, WI, were
inundated by riverine
flooding during the Midwest
floods of 2008.
Figure 2-4. The extreme
impact of large, fast-moving
waves, combined with the
removal of supporting soil
by erosion and scour, can
have devastating effects on
buildings exposed to coastal
flooding. Hurricane Floyd
destroyed this home along
the coast of North Carolina
in 1999.
Coastal flooding, which is caused by storm surge and wave
action, primarily affects coastal areas, especially those along
the beachfront, but it can also affect areas around bays and can
back up along rivers and streams that empty into bays. Coastal
flooding is most dangerous, and causes the most severe damage,
where large waves are driven inland by the wind (Figure 2-4).
These wind-driven waves occur primarily along the open coast,
where they can destroy homes, wash away protective dunes, and
erode the soil, often to the extent that the ground surface is low-
ered several feet. But they can also move inland where the land
is flat and there are no large dunes or other obstacles to break
them. In these areas, the level of damage can rival that along the
open coast.
DEFINITION
Storm surge is the rise in the level of
the ocean that results primarily from
strong winds associated with hurri-
canes and other storms. Decreased
atmospheric pressure from these
storms also makes a small contribu-
tion to storm surge.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 2-5
INTRODUCTION TO RETROFITTING 2
Coastal flooding can also move inland into low-lying areas
beyond the limit of wave action. The danger in these areas is
primarily from inundation due to storm surge but, even here,
fast-moving floodwaters can result in scour and erosion around
building foundations.
Another cause of flooding, which can affect homes outside
identified floodplains, is the limited capacity of local drainage
systems, including storm sewers, culverts, and drainage ditches.
These systems are usually designed to carry a specific amount of
water, which is referred to as the “design capacity” of the sys-
tem. When heavy rainfall over an area causes the design capacity
of the system to be exceeded, water will begin to back up and
fill low-lying areas near system inlets and along open ditches.
Depending on the amount and intensity of rainfall, the flood-
water may continue to rise and may eventually affect homes.
A similar problem occurs when drainage system inlets are
plugged or obstructed by mud or other debris and when drain-
age system outlets are submerged by water during riverine or
coastal floods. In the latter situation, water can flow backwards
in the system and reach areas that otherwise might not have
flooded.
2.3 How Flooding Can Damage Your
Home
To understand how flooding can damage your home, you need
to know about six important flood characteristics: depth/eleva-
tion, flow velocity, frequency, rates of rise and fall, duration,
and debris impact. Most of these characteristics apply to both
riverine and coastal flooding, and they can vary—sometimes
greatly—from one place to another. The flood conditions at a
particular site, such as the location of your home, are deter-
mined largely by the combination of these characteristics. The
following paragraphs explain these characteristics. Section 2.3
and Chapter 4 explain how you can determine the flood condi-
tions at your home.
2.3.1 Depth/Elevation of Flooding
The depth and elevation of flooding are so closely related that,
for the purposes of this discussion, they can be viewed as a sin-
gle characteristic. Flood depth is the height of the floodwater
above the surface of the ground or other feature at a specif-
ic point. Flood elevation is the height of the floodwater above
an established reference datum. The standard datums used by
DEFINITION
Wave action refers to the character-
istics and effects of waves that move
inland from an ocean, bay, or other
large body of water. Large, fast-mov-
ing waves can cause extreme erosion
and scour, and their impact on build-
ings can cause severe damage.
During hurricanes and other high-
wind events, storm surge and wind
increase the destructiveness of waves
and cause them to reach higher ele-
vations and penetrate further inland.
Scour refers to a localized loss of soil,
often around a foundation element.
Erosion refers to a general lower-
ing of the ground surface over a wide
area.
Intensity of rainfall refers to the
amount of rain that falls during a given
amount of time. It is usually expressed
in inches of rainfall per hour. The high-
er the number of inches per hour, the
greater the intensity.
DEFINITION
An elevation datum is an arbitrary
surface that serves as a common ref-
erence for the elevations of points
above or below it. Elevations are
expressed in terms of feet, meters,
or other units of measure and are
identified as negative or positive, de-
pending on whether they are above or
below the datum. Three common el-
evation datums are mean sea level
(msl), NGVD, and NAVD.
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2 INTRODUCTION TO RETROFITTING
most Federal agencies and many State and local agencies are the
National Geodetic Vertical Datum (NGVD) and the North Amer-
ican Vertical Datum (NAVD); however, other datums are also in
use. The use of other datums is important because elevations of
the ground, floodwaters, and other features cannot be meaning-
fully compared with one another unless they reference the same
datum. If a survey has established a benchmark, this point can
be used to determine the flood depth and elevation. When the
elevation of the ground (or another surface such as the lowest
floor of your home) and the elevation of the floodwaters both
use the same datum or benchmark, the flood depth at any point
is equal to the flood elevation at that point minus the eleva-
tion of the ground (or other surface) at that point. Figure 2-5
illustrates this relationship. Ground elevations are established
by surveys; flood elevations may be calculated or they may be
known from water marks left by past floods.
The depth of flooding at your home is important primar-
ily because floodwaters, even when they are not moving,
exert pressure on structural components such as walls and con-
crete floor slabs. The pressure exerted by still water is called
“hydrostatic pressure.” It is caused by the weight of the water,
so it increases as the depth of the water increases. As shown in
Figure 2-6, floodwater, including water that has saturated the soil
under the home, pushes in on walls and up on floors. The
upward force on floors is called “buoyancy.”
DEFINITION
A benchmark is a reference point es-
tablished by a survey with a precisely
known relationship to a datum.
Under the NFIP, the lowest floor of
a building is the floor of the lowest
enclosed area within the building,
including the basement. The only ex-
ception is an enclosed area below an
elevated building, but only when the
enclosed area is used solely for park-
ing, building access, or storage and
is compliant with relevant regulations.
The elevation of the lowest floor can
be very important in retrofitting, as you
will see in later chapters.
Buoyancy refers to the upward hy-
drostatic force that floodwater exerts
on the floors of homes with enclosed
spaces below the flood level.
Figure 2-5. In this example,
the 1-percent-annual-chance
flood elevation is 391.6
feet (10.1 feet above the
benchmark elevation of 381.5
feet), and the elevation of the
lowest floor of the home is
389.3 feet (7.8 feet above the
same benchmark). The flood
depth above the lowest floor
is therefore equal to 391.6
feet − 389.3 feet, or 2.3 feet
during the 1-percent-annual-
chance flood.
As shown in Figure 2-6b, water that has saturated the soil poses a special hazard for basement walls. Because
hydrostatic pressure increases with the depth of the water, the pressure on basement walls is greater than the pres-
sure on the walls of the upper floor, as indicated by the arrows in the figure. This pressure is made even greater by
the weight of the saturated soil that surrounds the basement.
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INTRODUCTION TO RETROFITTING 2
Figure 2-6. Hydrostatic
pressure acts on walls and
concrete slab floors. The
weight of saturated soils
adds to the pressure on
basement walls. Figure
2-6a shows a home with a
concrete slab floor. Figure
2-6b shows a home with a
basement.
The walls of homes built using standard wood-frame or
masonry construction are not designed to resist this pressure. If
the pressure exceeds the strength of the walls (including base-
ment walls), it can push them in or out (Figure 2-7), cause
extensive structural damage, and possibly cause the home to
collapse. In some areas, the buoyant force of hydrostatic pres-
sure on basement floors has pushed homes entirely out of the
ground.
If water is allowed to enter, the hydrostatic pressures on both
sides of the walls and floor become the same, or equalized
(Figure 2-8), and the walls are much less likely to fail. As
discussed in Chapters 3, 5, 7, and 8, this is an important consid-
eration in some types of retrofitting methods.
ment as “any area of the building
having its floor subgrade on all sides.”
Note that the NFIP definition of base-
ment does not include what is typically
referred to as a “walkout-on-grade”
basement, whose floor would be at or
above the surface of the ground that
touches the outside walls of the build-
ing on at least one side (see Section
3.1.2). This ground surface is referred
to as the “adjacent grade.”
DEFINITION
The NFIP regulations define a base-
Figure 2-7. The walls of this
basement in Wisconsin failed
because of the pressure
exerted by water and
saturated soil.
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2 INTRODUCTION TO RETROFITTING
Figure 2-8. Once water
enters the home, hydrostatic
pressure is equalized. Figure
2-8a shows a home with a
concrete slab floor. Figure
2-8b shows a home with a
basement.
2.3.2 Flow Velocity
Flow velocity is the speed at which floodwaters move. It is usually measured in feet per second (fps). Flow veloci-
ties during riverine floods can easily reach 5 to 10 fps and, in some situations, may be even greater. Expressing
velocities in fps is common in floodplain studies and engineering analyses. It may be helpful to relate fps to a more
familiar unit of measure. For example, 10 fps is roughly equal to 7 miles per hour (mph).
The velocity of riverine floodwaters depends on a number of factors; one of the most important is the slope of the
stream channel and floodplain. As you might expect, floodwaters will generally move much faster along streams
in steep mountainous areas than streams in flatter areas. However, even within the same floodplain, flow velocity
can still vary. As water flows over the ground, its velocity depends largely on the roughness of the ground surface.
For example, water will flow more swiftly over parking lots, roads, and other paved surfaces, and will flow more
slowly over ground covered with large rocks, trees, dense vegetation, or other obstacles. Also, flow velocities in the
floodplain will usually be higher nearer the stream channel than at the outermost fringes of the floodplain, where
water may flow very slowly or not at all. In areas subject to coastal flooding, velocities depend largely on the speed
of the wind and, like riverine flow velocities, on the slope and roughness of the ground surface.
If your home is in an area where floodwaters are flowing, especially if they are moving more than about 5 fps, the
flow velocity is important for several reasons. Flowing water pushes harder on the walls of a building than still
water. So instead of just the hydrostatic pressure caused by the weight of the floodwater resting against the walls
of your home, you have the additional pressure of moving water, referred to as “hydrodynamic pressure” (Figure
2-9). As water flows around your home, it pushes against the side of the home that faces the flow (the upstream
side). As it flows past the sides of the home, it creates friction that can tear at wall coverings, such as siding. On
the side of the home that faces away from the flow (the downstream side), the water creates a suction that pulls
on walls. In some situations, the combination of these forces can destroy one or more walls (Figure 2-10), cause
the home to shift on its foundation, or even sweep the home away.
Flowing water can also cause erosion and scour. As previously discussed, erosion refers to a general lowering of
the ground surface over a wide area. Scour refers to a localized loss of soil, often around a foundation element.
Both erosion and scour can weaken the structure of a home by removing supporting soil and undermining the
foundation. In general, the extent and depth of erosion and scour increase as the flow velocity and size of the
home increase. Also, keep in mind that any objects being carried by floodwaters will be moving at roughly the
same speed as the water. The dangers associated with these objects are discussed in Section 2.3.6.
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INTRODUCTION TO RETROFITTING 2
Figure 2-9. Moving water acts on the front, sides, and back of a home.
Figure 2-10. Water moving at
high velocity destroyed the
wall of this home and caused
the building to shift on its
foundation.
2.3.3 Flood Frequency
You may have been told that your home is in “the 100-year” floodplain, or you may have heard that term used to
describe a specific flood. You may also have heard similar terms used, such as “50-year flood” or “500-year flood.”
These terms can be misleading. Flood frequencies are usually determined through statistics and engineering
analyses performed by floodplain management agencies and other organizations responsible for implementation
of flood control programs and floodplain regulation. The results of those analyses define the probability, expressed
as a percentage, that a flood of a specific size on a specific stream will be equaled or exceeded in any year.
For example, the flood that has a 1 percent probability (1 in 100) of being equaled or exceeded in any year is
sometimes referred to as the 100-year flood. This term is simply a convenient way to express probability. It should
not be interpreted to mean a flood that happens exactly once every 100 years. Nor does it imply that once a
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2 INTRODUCTION TO RETROFITTING
100-year flood occurs there is little risk of another 100-year flood occurring in the near future. To the contrary,
changes in climatic conditions, such as those caused by El Niño, often result in clusters of floods that occur over
relatively short times at the same location. In this publication, the term 1-percent-annual-chance flood is used to
describe the 100-year flood.
For most homeowners, the value of these terms is that they indicate relative frequencies and sizes. Over time, a
1-percent-annual-chance (100-year) flood is expected to occur less often than a 2-percent-annual-chance (50-year)
flood and more often than a 0.2-percent-annual-chance (500-year) flood. In addition, a 1-percent-annual-chance
flood will be more severe than a 2-percent-annual-chance flood and less severe than a 0.2-percent-annual-chance
flood. For example, if your home is in the 1-percent-annual-chance floodplain of a nearby stream or river, the
1-percent-annual-chance flood elevation at your home will be lower than the 0.2-percent-annual-chance flood
elevation, and the water from a 2-percent-annual-chance flood might not even reach your home.
The 1-percent-annual-chance flood is particularly important for homeowners because it is the basis of NFIP flood
insurance rates and regulatory floodplain management requirements. These requirements are discussed in detail in
Section 2.5. In the NFIP, the 1-percent-annual-chance flood is referred to as the “base flood.” The elevation associ-
ated with the base flood is referred to as the “base flood elevation” (BFE), and the floodplain associated with the
base flood is referred to as the “special flood hazard area” (SFHA). Other Federal agencies, such as the U.S. Army
Corps of Engineers (USACE), use the 1-percent-annual-chance flood for planning and engineering design, as do
many State and local agencies. These agencies often have their own names for the 1-percent-annual-chance flood.
2.3.4 Rates of Rise and Fall
You may not have heard these terms before, but they describe important characteristics of flooding: how rapidly
the elevation (and therefore the depth) of water increases and decreases during a flood. These rates are usually
expressed in terms of feet or inches per hour. Floodwaters with high flow velocities, such as those in areas of steep
terrain, and water released by the failure of a dam or levee, usually rise and fall more rapidly than slower-moving
floodwaters, such as those in more gently sloping floodplains.
Rate of rise is important because it affects how much warning you will have of an impending flood. For example,
homeowners in the floodplains of large rivers like the Mississippi and Missouri may know days in advance that
flooding is occurring upstream and will eventually reach their homes. But in the floodplains of streams with rapid
rates of rise, homeowners may have only a few hours’ notice of a coming flood or perhaps none at all. With ad-
equate warning, you will be better prepared to take steps to protect yourself and your property. Warning time is
particularly important for flood protection methods that depend on action you must take. Chapters 3, 4, 7, and 8
further discuss this issue.
Rates of rise and fall are important also because of their effect on hydrostatic pressure. As explained in the
discussion of flood depth/elevation, hydrostatic pressure is most dangerous for a home when the internal and
external pressures are not equalized. This situation occurs when the level of water inside the home is significantly
higher or lower than the level outside. When floodwaters rise rapidly, water may not be able to flow into a home
quickly enough for the level inside the home to rise as rapidly as the level outside. Conversely, when floodwaters fall
rapidly, water that has filled a home may not be able to flow out quickly enough, and the level inside will be
higher than the level outside. In either situation, the unequalized hydrostatic pressures can cause serious structural
damage, possibly to the extent that the home collapses.
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INTRODUCTION TO RETROFITTING 2
2.3.5 Duration
Duration is how long a flood lasts, or how long it takes for the creek, river, bay, or ocean to return to its normal
level. As a homeowner, you may be more interested in how long floodwaters remain in or around your home
or perhaps how long they block nearby streets. In many floodplains, duration is related to rates of rise and fall.
Generally, water that rises and falls rapidly will recede more rapidly, and water that rises and falls slowly will recede
more slowly. An example of this relationship is the extensive flooding that occurred in the broad, flat floodplains
of the Midwest in 2008. In those areas, floodwaters rose slowly and remained high for many weeks or longer.
If your home is flooded, duration is important because it determines how long the structural members (such as
the foundation, floor joists, and wall studs), interior finishes (such as drywall and paneling), service equipment
(such as furnaces and hot water heaters), and building contents will be affected by floodwaters. Long periods of
inundation are more likely to cause greater damage than short periods. Duration can also determine how long
your home remains uninhabitable.
2.3.6 Debris Impact
Floodwaters can pick up and carry objects of all types—from small to large, from light to heavy—including trees,
portions of flood-damaged buildings, automobiles, boats, storage tanks, mobile homes, and even entire homes.
In cold climates, wintertime floods can also carry large pieces of ice. Dirt and other substances, such as oil, gaso-
line, sewage, and various chemicals, can also be carried by floodwaters. All of these types of debris add to the
dangers of flooding. Even when flow velocity is relatively low, large objects carried by floodwaters can easily damage
windows, doors, walls, and, more importantly, critical structural components of your home. As velocity increases,
so does the danger of damage from debris. If floodwaters carrying large amounts of dirt or hazardous substances
enter your home, damages may be greater. In addition, your cleanup costs are likely to be higher and your cleanup
time longer.
As you read the remaining sections of this guide, keep these flood characteristics and their effects in mind.
Section 2.3 and Chapter 4 explain how you can find out more about flooding in your area, including flood eleva-
tions near your home.
2.4 Other Hazards
Two more hazards you should be aware of are high winds (including hurricanes) and earthquakes. For homes
in areas subject to these hazards, some retrofitting methods are more appropriate than others. Chapters 3 and 4
further discuss this issue. But, regardless of the method you choose, if your home is in a high-wind or earthquake
hazard area, your design professional or contractor must ensure that all structural changes made can withstand not
only the expected flood forces, but the expected forces of winds or earthquakes as well.
Wind is similar to flowing water in that it pushes against the
side of the home that faces the wind and pulls on the side that
faces away (Figure 2-11). Wind passing over a home can exert
a lifting force on the home. The combination of push, pull, and
lift acts on the home, including the foundation, and can re-
sult in extensive damage if the structural system and building
envelope are not adequately designed and constructed.
DEFINITION
The building envelope is the entire
exterior surface of a building (includ-
ing walls, doors, and windows) that
encloses or envelopes the space
within.
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The ability of the wind to damage a building is increased if the wind or windborne debris breaches the building
envelope by breaking windows, collapsing doors, or puncturing walls. Once the envelope is breached, wind will
enter the building and the pressure on the walls and roof will increase, as shown in Figure 2-11. Wind and flood
forces can combine in different ways, depending on the directions of the wind and flood flow. When the wind and
flood flow direction are the same, the load on the home is greater than the load from either wind or flood alone.
Figure 2-11. Wind forces
on a sealed building are
less than wind forces on a
building with an opening.
The movement of the ground during an earthquake can place
large horizontal and vertical loads on a home (Figure 2-12).
Like the loads that result from flood flow and wind, earthquake
loads can cause extensive damage to a home if they have not
been accounted for in the structural design.
High-wind and earthquake hazards vary throughout the Unit-
ed States. In Chapter 4, you will find maps that show the areas
where these hazards are greatest. For more information on ret-
rofitting for wind refer to FEMA P-804, Wind Retrofit Guide for
Residential Buildings (FEMA.2010c), and for more information on
retrofitting for earthquakes refer to FEMA 232, Homebuilders’ Guide
to Earthquake-Resistant Design and Construction (FEMA. 2006).
2.5 Federal, State, and Local Regulations
In most communities throughout the United States, construction in floodplains is governed by combinations of
Federal, State, and local regulations; however, floodplain development can also be regulated wholly, or in part, by
the International Codes (I-Codes). The I-Codes are a comprehensive, consensus-based set of model building codes
that are often adopted at the State or local level. At the Federal level, FEMA administers the NFIP. Congress created
the NFIP in 1968 when it passed the National Flood Insurance Act (NFIA). The NFIP is a voluntary program for
communities. Its goal is to reduce the loss of life and the damage caused by flooding, to help the victims of floods,
and to lower the costs of flood damage borne by the taxpayer. Communities participate in the NFIP in several ways:
n Guiding future development away from flood hazard areas
n Requiring that new buildings, Substantially Improved existing buildings, and repair of Substantially
Damaged existing buildings in the SFHA be constructed in compliance with floodplain management
ordinance, regulation, or provisions of the building code intended to reduce flood damage
Figure 2-12. Earthquake forces act in both
horizontal and vertical directions.
Earthquake
Motion
Earthquake Motion
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INTRODUCTION TO RETROFITTING 2
n Providing floodplain residents with financial assistance
after floods
n Transferring the cost of flood losses from the taxpayer
to the owners of flood-prone buildings by requiring
the purchase of flood insurance for buildings in the
SFHA
The NFIP operates through a partnership between the Feder-
al Government, the States, and individual communities such as
counties and incorporated cities, towns, and villages.
A participating community adopts and enforces a floodplain
management ordinance, regulation, or provisions of the build-
ing code to regulate development within that floodplain,
including new construction, Substantial Improvement of exist-
ing buildings, and repair of Substantially Damaged buildings.
In return, federally backed flood insurance is made available to
property owners and renters who live in the community.
A participating community’s floodplain management ordi-
nance, regulation, or provisions of the building code must, at a
minimum, meet the requirements of the NFIP regulations, but
each community is free to establish additional or more stringent
requirements to provide additional protection. For example, the
regulatory floodplain defined by a community must include
the entire SFHA, but it may also include other flood hazard
areas within the community. Additionally, some States require
communities to adopt and enforce floodplain management
requirements that exceed the minimum requirements of the NFIP.
These points are particularly important because of their potential effect on your retrofitting project. In this guide,
you will find many references to requirements included within your community’s floodplain management ordi-
nance, regulation, or provisions of the building code. These are the minimum requirements that all communities
must adopt and enforce in their floodplain management ordinance, regulation, or provisions of the building code
to be compliant with the NFIP regulations. Remember that you must comply with your community’s requirements,
which may be more stringent.
Usually, communities enforce other requirements that affect construction, both inside and outside of the regula-
tory floodplain. These requirements include those associated with building codes and land use regulations, such
as zoning and subdivision ordinances.
2.5.1 The Community Rating System
The NFIP Community Rating System (CRS) is a voluntary incentive program that recognizes and encourages com-
munity floodplain management actions that exceed the minimum NFIP requirements. Flood insurance premiums
are discounted to reward community actions that meet the three goals of the CRS. The three goals of the CRS
are to:
DEFINITION
Under the NFIP, an improvement of
a building (such as reconstruction,
rehabilitation, or an addition) is con-
sidered a Substantial Improvement
if its cost equals or exceeds 50 per-
cent of the market value of the building
before the start of construction of the
improvement.
Similarly, damage to a building, re-
gardless of the cause, is considered
Substantial Damage if the cost of
restoring the building to its before-
damage condition would equal or
exceed 50 percent of the market val-
ue of the building before the damage
occurred. Consult your local officials
about determining the value of your
home.
For more information, consult your
local officials, or refer to FEMA P-758,
Substantial Improvement/Substantial
Damage Desk Reference (2010).
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n Reduce flood damage to insurable property
n Strengthen and support the insurance aspects of the NFIP
n Encourage a comprehensive approach to floodplain management
When communities participate in the CRS, flood insurance rates for insured property owners and renters are
discounted in increments of 5 percent to a maximum discount of 45 percent, based on 18 creditable activities.
The activities are organized under four categories:
n Public information (e.g., offering references on flood insurance and flood protection at the public library)
n Mapping and regulations (e.g., guaranteeing that a portion of currently vacant floodplain will be kept free
from development)
n Flood damage reduction (e.g., acquiring, elevating, and/or relocating flood-prone buildings so that they
are out of the floodplain)
n Flood preparedness (e.g., providing early flood warnings to the public)
To apply for CRS participation, a community submits documentation of its floodplain management activities to
the Insurance Services Office, which works on behalf of FEMA and the insurance companies. Specific information
about CRS and the application process can be found at the CRS online resource center at http://training.fema.gov/
EMIWeb/CRS/.
2.5.2 Flood Insurance Rate Maps
To provide communities with the information they need to enact and enforce floodplain management ordinance,
regulation, or provisions of the building code, FEMA conducts floodplain studies for communities throughout
the United States and publishes the results in Flood Insurance Studies (FISs) and FIRMs (Figure 2-13). The FIS
for your community provides information about the names and locations of flood sources; historical flood data;
flood elevations of varying frequency, including BFEs; areas inundated by the various magnitudes of flooding; and
boundaries of the SFHA and floodway. This information is presented on FIRMs, which are used by FEMA and
local communities to establish flood insurance rates.
DEFINITION
The regulatory floodway is the channel of a river or other watercourse and the adjacent land areas that
must be reserved in order to discharge the base flood without cumulatively increasing the water surface
elevation more than a designated height (44 CFR §59.1).
More simply put, the floodway is the portion of the SFHA where new development is strictly regulated to
prevent flood elevations from increasing. The flood hazard is usually greater in the floodway than in the
surrounding areas of the SFHA, referred to as the “floodway fringe.” Floodwaters in the floodway fringe
are typically shallower and have less velocity.
NFIP regulations do not prohibit development in all portions of the SFHA. Instead, the regulations re-
quire that residential buildings in the SFHA be elevated to or above the community’s BFE. But floodplain
development can reduce the amount of space available to pass floodwaters, which can increase flood
elevations. For this reason, the NFIP and local communities prohibit Substantial Improvement and new
construction in the floodway.
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INTRODUCTION TO RETROFITTING 2
Figure 2-13. This FIRM for riverine flooding shows the SFHA (Zone AE), floodway (hatch-marked Zone AE along centerline
of river channel), and areas outside the SFHA (Zone X). The area between the limits of the base flood and 0.2-percent-
annual-chance flood are delineated by shaded Zone X. Areas above the 0.2-percent-annual-chance flood are delineated by
unshaded Zone X.
FIRMs are available online at FEMA’s Map Service Center (MSC): http://www.msc.fema.gov. The site allows you to
search for your flood map in one of four ways:
n Searching for your address
n Using the catalog, which allows you to select your State, county, community, and flood map from a list
n Using a map search, which allows you to zoom into your community from a map of the United States
n Searching for a map panel by ID Number
Once you find your FIRM, you can create a printable FIRMette using the MSC Viewer. A FIRMette is a full-scale
section of a FEMA FIRM that you create for yourself online. There is no cost for making a FIRMette. FIRMettes are
used by many different parties such as community officials, mortgage lenders, real estate agents, design profes-
sionals, insurers, land developers, engineers, and surveyors.
The MSC Viewer allows you to zoom to the area you want to be included in your FIRMette and format your print-
able map. You can save your FIRMette either as an Adobe PDF file or as a TIFF file. The Map Service Center offers a
step-by-step tutorial on creating FIRMettes.
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Other Federal agencies, such as the USACE, U.S. Geological Survey, and Natural Resources Conservation Service
(formerly U.S. Soil Conservation Service), also publish flood information, as do some State and local agencies. This
information is often useful as a supplement to FISs and FIRMs. But, because it is developed to meet other needs,
it is not used for the NFIP unless it has been reviewed and approved by FEMA.
If you have questions about flood hazards in your community, including the limits of the regulatory floodplain,
flood elevations, or sizes and frequencies of past floods, check with your local officials. Usually, they will have
copies of the FIS and FIRM for your community. They can also help you determine whether your home is in the
regulatory floodplain and advise you about flood protection methods, including those described in this guide.
Local officials can also advise you about floodplain management requirements, building codes, and other require-
ments that may determine the types of changes you can make to your home. See Chapter 4 for more information
about working with local officials. You can also get help from your FEMA Regional Office (Appendix C) and the
office of your NFIP State Coordinator (Appendix D).
2.6 Financial Assistance for Retrofitting
2.6.1 Federal Programs
FEMA and other Federal agencies have an array of financial assistance programs that assist States, communities, and
individual property owners mitigate the negative effects of flood hazards. You may be eligible to receive financial
assistance through one or more of these programs that will help pay for some of the retrofitting projects docu-
mented in this guide. Check with your local officials, the FEMA Regional Office for your State (Appendix C), your
NFIP State Coordinator (Appendix D), or your State Historic Preservation Office (SHPO) (Appendix E).
If a Presidential Major Disaster Declaration has been issued for
your area, you may want to seek information from FEMA and
the State and local government representatives supporting the
post-disaster recovery of your community. Keep in mind that
funding for assistance programs is limited; often not everyone’s
needs can be met. Many Federal assistance programs provide
grants to State and local governments, who must then set priori-
ties for the use of the grant funds, including any potential use
by individual property owners. Additionally, not all methods of
retrofitting are eligible for funding.
Help from FEMA
Increased Cost of Compliance
One of the benefits provided by the NFIP is Increased Cost of
Compliance (ICC) coverage. If your home is covered by a Stan-
dard Flood Insurance Policy (SFIP), is in an SFHA, and has been
declared by your community to be Substantially Damaged or re-
petitively damaged by flood, ICC will help pay for certain types
of retrofitting. ICC coverage is available for most SFIPs.
NOTE
This section is not meant to be an
all-inclusive description of Federal
assistance. Following a Presidential
Major Disaster Declaration, State
and local officials will be briefed on
the available types of post-disaster
assistance.
NOTE
If a flood in your area is a federally de-
clared disaster, you must register with
FEMA to obtain assistance. The direc-
tions at http://www.fema.gov will walk
you through the application process.
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INTRODUCTION TO RETROFITTING 2
If your home sustains a flood loss and the community has declared it Substantially Damaged or repetitively
damaged, ICC will help pay the cost (up to $30,000 effective May, 2011) for the following retrofitting methods:
n Elevation: This raises your home to or above your community’s adopted design flood elevation (DFE) (see
Chapters 3 and 5).
n Relocation: This includes moving your home to another floodplain location on your lot and elevating it
or moving it completely out of the regulatory floodplain (see Chapters 3 and 6).
n Demolition: This razes your home and restores the original property (see Chapters 3 and 6).
As noted earlier, your community’s floodplain management ordinance, regulation, or provisions of the building
code must include a requirement for Substantial Damage. Substantial Damage as defined in Section 2.5.
Some communities may have adopted a cumulative Substantial Damage or repetitive loss provision so that
repetitively damaged buildings can qualify for an ICC claim payment. In order for buildings to qualify for a claim
payment under ICC coverage as a “repetitive loss structure” the building must be covered by a contract for flood
insurance and incur flood-related damages on two occasions during a 10-year period ending on the date of the
event for which the second claim is made, in which the costs of repairing the flood damage, on the average,
equaled or exceeded 25 percent of the market value of the building at the time of each such event. Note that ICC
availability under this provision applies only if the community has adopted a cumulative Substantial Damage or
repetitive loss provision in the floodplain management ordinance, regulation, or provisions of the building code.
Also, note that under the NFIP, communities are not required to adopt a repetitive loss provision in their flood-
plain management ordinance, regulation, or provisions of the building code.
Remember, communities with a more restrictive floodplain management ordinance, regulation, or provisions of
the building code may require a greater level of protection. If for example, your community requires new and
Substantially Improved or Substantially Damaged buildings to be elevated 1 or more feet above the BFE, ICC allows
for an ICC claim payment up to the $30,000 limit of coverage.
An ICC claim may also be paid for a combination of retrofitting actions. For example, ICC coverage allows for
a claim payment for the cost of demolition and elevation at the same or another site within the SFHA. The ICC
payment to demolish and elevate your home is limited to $30,000.
To learn more about ICC coverage, review your SFIP and contact your insurance agent, your community floodplain
management official, the FEMA Regional Office that serves your community (Appendix C), or the office of your
NFIP State Coordinator (Appendix D). If a Presidential Declaration of Major Disaster has been issued for your area,
you can get help from the Mitigation and Insurance Desk at the local DRCs. In many cases, the ICC payments are
used to offset the non-Federal cost-share to participate in a disaster assistance program.
Unified Hazard Mitigation Assistance Program
FEMA’s Hazard Mitigation Assistance (HMA) grant programs present a critical opportunity to reduce the risk to
individuals and property from natural hazards while simultaneously reducing reliance on Federal disaster funds.
Hazard mitigation is the only phase of emergency management specifically dedicated to breaking the cycle of
damage, reconstruction, and repeated damage. HMA programs provide pre- and post-disaster funding to States,
Territories, Indian Tribal governments, local governments, and eligible private non-profits (PNPs) for activities
that are consistent with the National Mitigation Framework’s Long-term Vulnerability Reduction capability. Quali-
fied private non-profits (PNPs) and individual homeowners are also eligible to receive HMA grant funds, but they must
apply through a State agency or local government.
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The statutory origins of each HMA program differ, but their goals are the same: reduce community vulnerability
to disasters, promote individual and community safety and resilience, promote community vitality after an inci-
dent, and reduce response and recovery resource requirements in the wake of a disaster. Three grant programs are
currently included in the Unified HMA program:
The Hazard Mitigation Grant Program (HMGP) is authorized by Section 404 of the Robert T. Stafford Disaster
Relief and Emergency Assistance Act, as amended (the Stafford Act), Title 42, United States Code (U.S.C.) 5170c.
The key purpose of HMGP is to ensure that the opportunity to take critical mitigation measures to reduce the risk
of loss of life and property from future disasters is not lost during the reconstruction process following a disas-
ter. HMGP is authorized by a Presidential Declaration of Major Disaster. A Governor may request HMGP funding
be available throughout the State or only in specific jurisdictions. The amount of HMGP funding available to the
Applicant is based upon the estimated total Federal assistance to be provided by FEMA for disaster recovery under
the Presidential Declaration of Major Disaster.
The Pre-Disaster Mitigation (PDM) program is authorized by Section 203 of the Stafford Act, 42 U.S.C. 5133.
The PDM program is designed to assist States, Territories, Indian Tribal governments, and local communities to
implement a sustained pre-disaster natural hazard mitigation program to reduce overall risk to the population and
structures from future hazard events, while also reducing reliance on Federal funding from future disasters. PDM
provides funds on an annual basis.
The Flood Mitigation Assistance (FMA) program is authorized
by Section 1366 of the NFIA, 42 U.S.C. 4104c, with the goal of
reducing or eliminating claims under the NFIP. FMA provides
funds on an annual basis.
The National Flood Insurance Fund provides the funding for the
FMA program. The PDM and FMA programs are subject to the
availability of appropriation funding, as well as any program-
specific directive or restriction made with respect to such funds.
Table 2-1 provides a summary of eligible retrofit activi-
ties for each of the three programs in the Unified HMA
Program. More information about each program can be
found on the FEMA HMA Web site at https://www.fema.gov/
hazard-mitigation-assistance.
CROSS REFERENCE
The Repetitive Flood Claims (RFC)
program and the Severe Repetitive
Loss (SRL) program have been elim-
inated and significant changes have
been made to the FMA program.
For more information, refer to the
Unified Hazard Mitigation Assistance
Guidance.
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INTRODUCTION TO RETROFITTING 2
Table 2 1. Eligible Retrofit Activities by Program
Elibigle Activities HMGP FMA
Acquisition/Demolition (for purposes of open space)4 4
Relocation 4 4
Elevation 4 4
Dry Floodproofing (historic residential structures)4 4
Mitigation Reconstruction 4
Help from Other Federal Agencies
Several Federal agencies offer disaster assistance to communities and citizens. For a complete list of Federal assis-
tance programs for which you are eligible, visit http://www.disasterassistance.gov.
Small Business Administration (SBA)
SBA provides low interest disaster loans to homeowners, renters, businesses of all sizes, and PNP organizations to
repair or replace real estate, personal property, machinery and equipment, inventory, and business assets that have
been damaged or destroyed in a declared disaster. Visit http://www.sba.gov/services/disasterassistance/ for more
information.
U.S. Department of Housing and Urban Development (HUD)
HUD provides flexible grants to help cities, counties, and States recover from Presidentially Declared Major Disas-
ters, especially in low-income areas, subject to availability of supplemental appropriations. Visit http://www.hud.
gov/ for more information.
U.S. Army Corps of Engineers (USACE)
The USACE has the statutory authority to participate in flood protection projects that may include residential
retrofitting (including elevating flood-prone homes and acquiring badly damaged flood-prone homes). Contact
the appropriate USACE Division office for further information. You can find more information and contact infor-
mation for your USACE Division office at http://www.usace.army.mil.
Natural Resources Conservation Service (NRCS), U.S. Department of Agriculture (USDA)
The NRCS has the statutory authority to participate in small watershed flood protection projects that may include
residential retrofitting. Contact your local Conservationist for further information. More information is available
at http://www.nrcs.usda.gov.
Other Assistance Programs
Other Federal programs intended to protect and improve the environmental quality of floodplains may offer
financial assistance.
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2.6.2 Non-Federal Help
Programs Sponsored by State and Local Governments
States, local governments, and flood control and drainage districts sometimes develop financial assistance pro-
grams to promote flood hazard retrofitting projects. Ask your local officials whether such a program exists in your
community.
Voluntary Organizations
After floods and other major disasters, voluntary organizations often offer their services to support the rebuilding
of homes. Occasionally, materials are donated and volunteers offer to provide labor that could be used to reduce
the cost of a retrofitting project. Check with local officials, local service organizations, and homes of worship for
information about such services. Note that you must obtain building permits and comply with all relevant regu-
lations (including Substantial Damage requirements, if they apply), even if you receive assistance from voluntary
organizations.
Environmental Interest Organizations, Including Land Trusts and Nature Conservancies
Numerous non-government, non-profit, and quasi-public organizations are dedicated to enhancing the environ-
mental benefits of floodplains. Sometimes these organizations provide funds that can be used in the restoration or
protection of the natural beneficial value of the floodplain.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-1
3.0 An Overview of the
Retrofitting Methods
This guide describes six retrofitting methods for you to consider as you think about how to protect your home
from flooding:
Elevation – Raising your home so that the lowest floor or lowest horizontal member is at or above the
regulated flood level. You can accomplish this in several ways. (Chapter 5)
Relocation – Moving your home to higher ground where it will reduce the exposure to flooding.
(Chapter 6)
Demolition – Tearing down your damaged home and either rebuilding on the same property or buying
or building a home elsewhere. (Chapter 6)
Wet Floodproofing – Making portions of your home resistant to flood damage and allowing water to
enter during flooding. (Chapter 7)
Dry Floodproofing – Sealing your home to prevent floodwaters from entering. (Chapter 7)
Barrier Systems – Building a floodwall or levee around your home to restrain floodwaters. (Chapter 8)
This chapter describes the six methods in detail. Keep in mind that only elevation, relocation, allowable wet
floodproofing, and demolition can be used to meet the minimum requirements of the NFIP. Barrier systems, dry
floodproofing, and some wet floodproofing may be used to minimize damages, but are not recognized as meeting
the minimum requirements of the NFIP. Remember that purchasing flood insurance for your home is important,
even if you mitigate using one of these methods.
While the aforementioned mitigation methods protect the actual structure, this guide also describes retrofitting
options for equipment and utilities to consider as you think about how to protect your home from flooding:
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3 AN OVERVIEW OF THE RETROFITTING METHODS
Equipment/Utilities – Equipment/Utilities – Retrofitting existing building equipment and utility sys-
tems may involve a combination of elevating and/or protecting in place. (Chapter 9)
For each method, you will find a section that explains how the method works and where it should
and should not be used, lists its advantages and disadvantages, and provides a relative cost estimate. But first, you
should be aware of some general cautions about retrofitting.
WARNING
In the areas listed below, the risks to lives and property are usually greater than in other flood-prone
areas:
• Coastal High Hazard Areas (insurance Zone V, VE, and V1–V30) shown on a FIRM (Figure 2-13)
• Coastal A zones (portion of Zone A seaward of the limit of moderate wave action (LiMWA))
• Floodways shown on a FIRM (see Figure 2-13)
• Alluvial fan flood hazard areas (certain Zone AO with depths and velocities) shown on a FIRM
• Areas subject to flash floods
• Areas subject to ice jams
• Areas subject to extremely high-velocity flood flows
Modifying a home to protect it from flood damage in these areas requires extreme care and may also
require complex, engineered designs. If your home is in one of these areas, relocation or demolition (as
described later in this chapter and in Chapter 6) may be a more conservative option rather than any of
the other retrofitting methods discussed in this guide. If you have any doubt about whether your home is
in an area of unusually severe hazard, consult your local officials.
3.1 Cautions
3.1.1 Substantial Improvement/Substantial Damage
As noted in Chapter 2, your community’s floodplain manage-
ment ordinance, regulation, or provisions of the building code
includes restrictions on the types of changes that may be made
to a home that is being Substantially Improved or that has sus-
tained Substantial Damage. These restrictions prohibit or limit
the use of some retrofitting measures. Two of the six methods
described in this guide—dry floodproofing and levees/flood-
walls—can reduce future damage but may not be used to bring
a Substantially Improved or Substantially Damaged home into
compliance with your community’sfloodplain management ordinance, regulation, or provisions of the building
code. Instead, in accordance with your community’s requirements, you must do one of the following:
n Move the home out of the regulatory floodplain
n Elevate the home so that its lowest floor is at or above the BFE
n In conjunction with elevation, wet floodproof the areas of the home below the BFE and use them only
for parking, building access, or storage
NOTE
Substantial Improvement and
Substantial Damage are defined in
Section 2.5 and Appendix B.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-3
AN OVERVIEW OF THE RETROFITTING METHODS 3
n Demolish the home and either rebuild or buy a home elsewhere
Additional requirements apply to the use of wet floodproofing.
These are described later in this chapter and in Chapter 7.
3.1.2 Basements
Another important floodplain management requirement con-
cerns basements. If your home has a basement below the BFE
and your local officials determine that it is being Substantially
Improved or is Substantially Damaged, the basement must be elimi-
nated. You can usually do this by backfilling it with compacted
soil or other suitable material. For floodplain management pur-
poses, the NFIP regulations define a basement as “any area of the
building having its floor subgrade on all sides.” Your communi-
ty’s floodplain management ordinance, regulation, or provisions
of the building code may include a more restrictive definition
of basement.
Note that the NFIP definition of “basement” does not include
what is typically referred to as a “walkout-on-grade” base-
ment, whose floor would be at or above adjacent grade on at
least one side of the building. Depending on your community’s
floodplain management ordinance, regulation, or provisions of
the building code, the requirement to eliminate the basement in
a Substantially Improved or Substantially Damaged home may not
apply to a walkout-on-grade basement. Instead, you may be able
to wet floodproof the area. However, a wet floodproofed walk-
out-on-grade basement may be used only for parking, building
access, or storage.
Your local officials can tell you more about these requirements
and others that may be specified by local building codes and or-
dinances (see Chapter 4).
3.1.3 Flood Protection Elevation and Risk
When you retrofit your home, one of the most important
things you will do is choose a level of flood protection. In oth-
er words, will you protect your home from the base flood, the
0.2-percent-annual-chance flood, or some other flood? In some
instances, this decision will be entirely yours; in others, it will
depend largely on the regulatory requirements of your commu-
nity, your State, or both. If your retrofit project is being funded
through a Federal, State, or local agency, you may also be sub-
ject to different regulatory requirements. For the purpose of this
publication, the flood protection elevation is considered the
flood protection level you choose for your home.
DEFINITION
Walkout-on-grade is a term com-
monly used to describe a basement
whose floor is at ground level on at
least one side of a home. The term
“walkout” is used because most base-
ments of this type have an outside
door or doors (entry door, garage
door, or both) at ground level (see fig-
ure below). Note that if a basement
floor is below grade on all sides (a
basement as defined by the NFIP reg-
ulations) the basement may still have
an outside door, but the door will be
below ground level and stairs will be
required for access.
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DEFINITION
Flood protection elevation – The elevation you choose to protect your home against the flood haz-
ard. Although it is feasible for you to have a flood protection elevation less than the DFE, protecting your
home to at least the DFE is recommended.
Design flood elevation (DFE) – The elevation of the design flood relative to the datum specified on the
community’s FIRM or flood hazard map. The design flood is the greater of the following two flood events:
(1) the base flood, affecting those areas identified as special flood hazard areas on the community’s
FIRM; or (2) the flood corresponding to the area designated as a flood hazard area on a community’s
flood hazard map or otherwise legally designated. The I-Codes, ASCE 7, and ASCE 24 use the term
DFE. In many communities, the DFE is identical to the BFE. Communities may designate a design flood
(or DFE) in order to regulate based on a flood of record, to account for future increases in flood levels
based on upland development, or to incorporate freeboard.
Base flood elevation (BFE) – The elevation of the base flood relative to the datum specified on a com-
munity’s FIRM. The base flood has a 1 percent chance of being equaled or exceeded in any given year.
BFEs are shown on FIRMs for many SFHAs. Relative to NFIP requirements, the BFE is the minimum
elevation to which the lowest floor of a building must be elevated or floodproofed (Zone A). In Zone V, the
bottom of the lowest horizontal structural member must be elevated to or above the BFE; floodproofing
is not permitted in Zone V. Many SFHAs are shown on FIRMs without BFEs; in these areas, community
officials and permit applicants are required to obtain and use information from other sources, or must
estimate or develop BFEs at specific locations.
Freeboard – An added margin of safety, expressed in feet above a specific flood elevation, usually the
BFE. In States and communities that require freeboard, buildings are required to be elevated or flood-
proofed to the higher elevation. For example, if a community adopts a 2-foot freeboard, buildings are
required to be elevated or floodproofed to 2 feet above the BFE.
As you will see in this chapter, different retrofitting methods protect your home in different ways. For example,
when you elevate your home, you protect it by raising its lowest floor to a specified elevation. When you dry
floodproof your home, you use sealants, shields and other measures to protect the part of your home below a
specified elevation by preventing water from entering the building. Because some seepage is anticipated, sump
pumps are used to control the seepage and flood-damage-resistant materials are used to prevent damage where
seepage is likely to occur. The home’s structural components must have the capacity to resist increased flood loads
resulting from dry floodproofing. To wet floodproof, you allow floodwaters to enter your home, but prevent
damage below a specified elevation by using flood-damage-resistant materials and construction techniques. When
you protect your home with a levee or floodwall, the top of the levee or floodwall is constructed to a specified
elevation. To meet the requirements of the NFIP and potentially reduce your flood insurance premium, FEMA
recommends protecting your home to the DFE.
If your home is being Substantially Improved or has been Substantially Damaged, your community’s floodplain
management ordinance, regulation, or provisions of the building code will specify a DFE that is at least equal
to the BFE (the elevation of the 1-percent-annual-chance flood). Communities may require a higher DFE if they
wish, or they may be required to do so by State law. Some States and communities require a higher DFE by estab-
lishing freeboard requirements, as discussed in Section 3.1.4. Your local officials can advise you about this.
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AN OVERVIEW OF THE RETROFITTING METHODS 3
On the other hand, if NFIP compliance is not required (the building does not have to meet the requirements of
Substantial Improvement/Damage), then you may choose to have a flood protection level less than the DFE.
Although you cannot use a flood protection elevation lower than that required by your community, you are prob-
ably free to use a higher elevation if you wish to provide a greater level of flood protection. Depending on your
situation, your choice of flood protection method and optimal elevation will be based largely on the cost to el-
evate to different elevations, the risk reduction provided by different elevations, and the annual cost of insurance
premiums at different elevations.
In general, you will find that the cost of retrofitting increas-
es as your flood protection elevation increases. For example,
protecting your home to the elevation of the 2-percent-annual-
chance flood with one of the methods described in this guide
will probably cost you less than protecting it to the BFE with the
same method (although the additional cost to protect to the BFE
may be small). Although using a lower flood protection eleva-
tion may result in a less expensive retrofitting project, it exposes
your home to a greater risk of flood damage and higher insur-
ance rates. So in choosing a flood protection elevation, you must
consider not only how much you are willing to pay, but also the
level of risk you are willing to accept, including the potential
for damage, financial loss, and emotional distress. For example,
recent studies have shown that adding 1 to 3 feet of freeboard
above the BFE to an elevation project can pay for itself within a
few years through a 25 to 60 percent annual reduction in flood
insurance premiums.
One way to see the relationship between your flood protection
level and risk is to look at the probabilities associated with floods
of various magnitudes during a period of 30 years, which is also
the same length of a standard mortgage (Figure 3-1). The percentages shown along the vertical axis of the graph
in Figure 3-1 are the probabilities that a flood will be equaled or exceeded during a 30-year period. This prob-
ability decreases as the magnitude of the flood increases. So the probability of a flood with an elevation equal to
or greater than the flood protection elevation you choose decreases as your flood protection elevation increases.
For example, compare the risks associated with the 2-percent-annual-chance (50-year) flood and the base flood.
If you choose a flood protection elevation equal to the elevation of the 2-percent-annual-chance (50-year) flood,
the probability that a flood as high as or higher than your flood protection elevation will occur during a 30-year
period is 45 percent. But if you choose a flood protection elevation equal to the 1-percent-annual-chance flood
(100-year flood or base flood), the probability drops to 26 percent. Although the base flood serves as the basis
for NFIP insurance rates and regulatory floodplain management requirements, the relative frequency of any given
flood (e.g., 2- year or 10-year) serves as a useful reference point when selecting a retrofitting option, evaluating
cost effectiveness, and comparing relative risk.
Regardless of the flood protection elevation you choose or are required to use, you must realize that a larger flood
is always possible and that there will always be some risk of damage. If you don’t have flood insurance, you should
purchase a policy; if you have flood insurance, you should maintain your policy, even if you have protected your
home to or above the BFE. Once a home has been retrofitted to meet the NFIP requirements for Substantially Im-
proved structures, it will probably be eligible for a lower flood insurance rate depending on the level of protection
NOTE
A single-story home that is valued
at $150,000 and located in Zone AE
can have differing insurance premi-
ums based on the level of protection.
If the home is elevated to the BFE
and does not have an enclosure, the
annual premium would be approxi-
mately $1,294. If the same home is
elevated to 2 feet above the BFE, the
annual premium would be approxi-
mately $389. The increase in the flood
protection level would result in a 70
percent savings in annual insurance
premiums that would be passed onto
the homeowner.
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of your flood retrofit. Note that dry floodproofing of residential structures is not permitted to meet NFIP require-
ments, and is not recognized for flood insurance premium reduction purposes. Also, unless a floodwall or levee is
accredited, it is not recognized for flood insurance premium reduction purposes.
Figure 3-1. This graph shows
the relationship between
flood recurrence intervals
and the probability of an
event occurring within a 30-
year period.
3.1.4 Freeboard and Flood Mapping Uncertainties
If you are protecting your home by elevating it, dry floodproofing it, or building a levee or floodwall, you should
include a minimum of 1 foot of freeboard in your flood protection elevation, even if your community does not
require you to do so. For example, if you are elevating your home to protect it from the base flood, your flood
protection elevation should be equal to the BFE plus 1 foot.
Freeboard is recommended because of uncertainties regarding
expected flood elevations. These uncertainties exist for several
reasons, but the two primary reasons are limitations of the ana-
lytical methods used in floodplain studies and potential effects
of future watershed development, such as the construction of
buildings and roads.
FEMA and other agencies that perform floodplain studies use
a variety of standard engineering methodologies to determine
flood frequencies and flood elevations. These methods involve the use of historical data, field measurements,
and assumptions and judgments, all of which can affect the accuracy of the results. Some amount of uncer-
tainty regarding the results is, therefore, unavoidable, and the potential for flood elevations higher than those
expected should always be accounted for in retrofitting. For example, FEMA’s FIRMs include areas subject to the
0.2-percent-annual-chance flood (designated on FIRMs as Zone B or shaded Zone X) and areas outside of the
0.2-percent-annual-chance flood (designated on FIRMs as Zone C or unshaded Zone X). Homes constructed in
Zones B, C, or X are not considered to have a high risk of flooding by the NFIP, but that does not mean that they
DEFINITION
The watershed of a stream is the
geographic area that contributes sur-
face water, from rain or melting snow,
to that stream.
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AN OVERVIEW OF THE RETROFITTING METHODS 3
are not subject to flooding. In fact, 25 to 30 percent of all flood insurance claims are for flood damages that occur
in one of these zones.
Another example of uncertainties in mapping exists in coastal areas. Coastal FIRMs show Coastal High Hazard Ar-
eas (designated on FIRMs as Zones V, VE, and V1–V30), which are subject to waves of 3 feet or higher. However,
historic observations have shown that many coastal homes located outside of Zone V areas still experience sig-
nificant damage from moderate wave heights of 1.5 to 3 feet. For this reason, FEMA is working to update many
coastal FIRMs to include SFHAs seaward of the LiMWA, also known as Coastal A Zones. Zone A in coastal areas
is divided by the LiMWA. The LiMWA represents the landward limit of the 1.5-foot wave. The area between the
LiMWA and the Zone V limit is known as the Coastal A Zone for building code and standard purposes and as the
Moderate Wave Action (MoWA) area by FEMA flood maps. Again, this area is subject to wave heights between 1.5
and 3 feet during the base flood. The area between the LiMWA and the landward limit of Zone A due to coastal
flooding is known as the Minimal Wave Action (MiWA) area and is subject to wave heights less than 1.5 feet dur-
ing the base flood. Although not an NFIP requirement, FEMA recommends that homes located in Coastal A Zones
meet the same requirements as homes constructed in Zone V areas. Figure 3-2 is a typical paper FIRM showing
the delineations between Zone V, the MoWA area, the LiMWA, Zone A, and the MiWA area. Figure 3-3 is an ex-
ample of a transect perpendicular to the shoreline showing the delineations between Zone V, the MoWA area, the
LiMWA, Zone A, and the MiWA area.
Figure 3-2. Portion of a
paper FIRM showing coastal
flood insurance rate zones.
The icons on the right
indicate the associated flood
hazard zones for design
and construction purposes.
The LiMWA is not shown on
older FIRMs, but is shown on
newer FIRMs.
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Figure 3-3. Typical transect perpendicular to the shoreline showing the delineations between Zone V, the MoWA area, the
LiMWA, Zone A, and the MiWA area.
Development in a watershed can increase the size and frequency of floods in that watershed. In general, water-
shed development reduces the amount of open ground available to absorb water from rain and melting snow and,
therefore, increases the amount of water that makes its way into streams. As a result, in a developing watershed,
an amount of rainfall that might have caused minor floods in the past may cause larger floods and higher eleva-
tions in the future.
FEMA’s floodplain studies are based on the watershed conditions existing at the time the studies are performed.
They do not account for potential increases in watershed development or any other changes that might affect the
sizes of future floods. The reason for this approach is that one of the primary purposes of FISs and FIRMs is to pro-
vide the technical basis for establishing flood insurance rates. Therefore, the flood hazards must be shown as they
are, not as they might be. Also, attempting to predict the level of future watershed development in every study and
determine the effects not only would be extremely difficult but also would require additional assumptions and
judgments that could increase uncertainty. However, in many watersheds, some amount of development is inevita-
ble. So, providing freeboard is a prudent means of protecting against the increased flood elevations that may result.
3.1.5 Human Intervention
Retrofitting methods fall into two general categories: those that
depend on human intervention, which are referred to as “ac-
tive” methods, and those that do not, which are referred to as
“passive” methods. For example, elevating your home does not
require human intervention to be effective. But what if you have
a floodwall with an opening for your car? In addition to requir-
ing interior drainage, a floodwall with an opening will protect
your home only if you can close the opening before flooding
occurs. So your floodwall will have to be fitted with a gate (or
some other type of closure mechanism), and every time flood-
ing threatens, you will have to be warned far enough in advance
so that you can close the gate in time.
DEFINITION
Human intervention is any action
that a person must take to enable a
flood protection measure to function
as intended. This action must be tak-
en every time flooding threatens.
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The need for adequate warning time and human intervention
makes active methods less reliable than passive methods. You
should try to avoid active methods when you choose a ret-
rofitting method for your home, keeping in mind that active
methods cannot be used to bring a home into compliance with
the NFIP. If your retrofitting project includes active methods,
you must have a plan that describes what actions you will take to
make the measures work and when you will take those actions.
3.1.6 Other Considerations
The retrofitting measures discussed in this guide may be the best means of protection for a home in an area where
a large flood control project or major waterway improvement, is not feasible, warranted, or appropriate. You
should keep the following in mind whenever you consider a retrofitting project:
n Communities participating in the NFIP require permits for all development within the regulatory
floodplain. Under your community’s floodplain ordinance or law, any changes to buildings and other
structures are considered “development.” These changes include improvements and repairs of existing
buildings and other structures. Also, communities usually require building permits for many of the
activities associated with the retrofitting methods described in this guide. In communities that have
adopted a floodplain ordinance or law, health code, and building code, the permits required by these
ordinances, laws, and codes may be issued separately or as one combined permit. You may need a permit
for the following:
o Modifying your existing home or building a new
home on a flood-prone site. A floodplain permit
and possibly a building permit will be required.
o Moving a home on public rights-of-way. If you
relocate your home, you will probably need
a permit, not only from your community but
also from your State, as well as from any other
communities through which the home will pass
on its way to the new site. A relocation project may
also require a permit for the foundation at the new
site.
o Demolishing a damaged home and restoring the
site after demolition, including grading, planting
vegetative cover, capping and abandoning utilities,
and removing or securing underground septic and
fuel storage tanks.
You may wish to obtain the permits necessary for
your retrofitting project yourself or arrange for your
retrofitting contractor or design professional to obtain
them. But remember, you must have the necessary
permits in hand before you begin your project. As
discussed in Chapter 4, your local officials are the best
source of information about State and local permit
requirements.
WARNING
Some communities may restrict or
prohibit the use of active retrofitting
methods for flood protection.
CROSS REFERENCE
Your design professional or contrac-
tor should review some or all of the
applicable versions of the follow-
ing nationally recognized codes and
standards:
• International Code Council,
International Building Code (IBC)
• International Code Council,
International Existing Building
Code (IEBC)
• International Code Council,
International Residential Code
(IRC)
• ASCE, Minimum Design
Loads for Buildings and Other
Structures (ASCE 7)
• ASCE, Flood Resistant Design
and Construction (ASCE 24)
• See Appendix A for more
information.
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3 AN OVERVIEW OF THE RETROFITTING METHODS
n In addition to meeting the requirements of the floodplain management ordinance and building codes,
you may need to comply with the requirements of other Federal, State, and local laws and ordinances, such as those
dealing with zoning setbacks and wetlands. Again, your local officials are the best source of information about
these requirements.
n If your retrofitting project will involve financial assistance from a Federal agency and your property is 50
years old or older, you must work with that agency to ensure that your project complies with the National Historic
Preservation Act (16 U.S.C. 470). The act requires that, before releasing any Federal assistance, the agency
determine whether the property is eligible for inclusion in the National Register of Historic Places and if
so, whether your project will have any effect on the historic character of the property. This requirement
may not apply in some emergency situations or if the agency has made prior arrangements with historic
preservation officials. For more information, contact your SHPO (Appendix E).
n Most retrofitting measures should be designed and constructed by experienced professionals, such as contractors,
engineers, and architects. Using professionals helps you make sure that the work is done properly, that
code and regulatory requirements are met, and that, once completed, the retrofitting measures will work.
n Most retrofitting measures cannot be simply installed and forgotten. You will need to periodically inspect
and maintain them to be sure that they will continue to work over time, especially if they require human
intervention or depend on certain materials.
n Even though retrofitting will help protect your home from flooding, you should never remain in your home during
flooding. Stay informed about flooding conditions by monitoring local radio and television stations. Be
prepared to evacuate when necessary.
n Elevating your home may reduce the cost of your NFIP flood insurance policy. Relocating a home to a
site outside the regulatory floodplain eliminates the mandatory flood insurance purchase requirement
and significantly reduces the cost of flood insurance for an owner who wishes to purchase a policy.
3.2 Construction Terminology
In the remainder of this guide, you will find many references to common types of home construction, such as
frame or masonry, and common types of home foundations, such as slab-on-grade or crawlspace. Even if you are
already familiar with these and other home construction terms, take a minute to review the following information
before you move to the descriptions of the retrofitting methods.
3.2.1 Construction Type
The most common home construction types are (Figure 3-4):
Frame – walls constructed of wood or light-gauge metal studs, with wood, vinyl, or aluminum siding
Masonry veneer – frame walls with a non-structural, decorative, exterior layer of brick, stone, or concrete block
instead of siding
Masonry – walls constructed of brick, stone, or concrete block
Modular home – frame home assembled on site on a permanent foundation from separate sections manufactured
elsewhere (subject to local building codes)
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Manufactured home – prefabricated frame home constructed on a transportable frame that can be placed on a
permanent or temporary foundation (subject to Federal and State standards)
Some homes consist of combinations of two or more of these construction types.
Figure 3-4. Typical cross-sections of three common construction types: frame, masonry veneer, and masonry. The
foundation shown here for all three construction types consists of concrete blocks and a concrete footing. The same
construction types are also found on basement and slab-on-grade foundations.
3.2.2 Foundation Type
Most homes of the construction types listed above are built on
the following types of foundations (Figure 3-5):
Basement – with masonry or cast-in-place concrete walls
Crawlspace – with masonry or cast-in-place concrete walls
Slab-on-grade – either a slab with a masonry or concrete foun-
dation or a thickened slab (see Figure 5-5 in Chapter 5)
Open foundation – usually concrete or masonry piers, but
sometimes wood, concrete, or metal posts, columns, or piles
Some homes are built on more than one type of foundation. Var-
ious combinations of basement, crawlspace, and slab-on-grade
foundations are common. Manufactured homes are occasionally
installed on basement or crawlspace foundations but are more
often supported either by stacks of concrete blocks or by foun-
dation systems designed specifically for manufactured homes.
DEFINITION
Concrete poured into forms at the
construction site is referred to as
cast-in-place concrete.
WARNING
The relative costs in this chapter are
provided only as examples of what to
expect when choosing a retrofitting
method. Be sure to get a complete,
written cost estimate from your con-
tractor and design professional before
you begin any retrofitting project (see
Chapter 4).
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Figure 3-5. Home foundation types.
3.3 Retrofitting Methods and Costs
The following sections give an overview of the six retrofitting
methods, explain how they work and where they are appro-
priate, and list their advantages and disadvantages. With this
information, you will be ready for Chapter 4, Deciding Which Meth-
od Is Right for Your Home.
3.3.1 Elevation
Elevating a home to prevent floodwaters from reach-
ing living areas is an effective retrofitting method.
The goal of the elevation process is to raise the lowest
floor to or above the DFE. You can do this by elevating
the entire home, including the floor, or by leaving the home in
its existing position and constructing a new raised floor with-
in the home. The method used depends largely on construction
type, foundation type, and flooding conditions. Chapter 5 pres-
ents more detailed information on elevation.
During the elevation process, most homes (including manufac-
tured homes) are separated from their foundations, raised on
hydraulic jacks, and held by temporary supports while a new or
extended foundation is constructed below. This method works
well for homes originally built on basement, crawlspace, and
open foundations. As explained later in this section, the new or
extended foundation can consist of continuous walls or separate
piers, posts, columns, or piles.
CROSS REFERENCE
FEMA P-550, Recommended
Residential Construction for Coastal
Areas: Building on Strong and Safe
Foundations (FEMA. 2009), offers
more detail about these foundation
types and elevation.
NOTE
When you elevate your home, the
existing foundation will need to be ex-
tended or demolished and rebuilt. This
decision will depend on the condition
of the existing foundation and its abil-
ity to carry additional loads.
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For homes with slab-on-grade foundations, elevation can be
done in one of two ways. One approach is to leave the home
attached to the slab foundation and lift both together. After the
home and slab are lifted, a new foundation is constructed below
the slab. The other approach is to detach the home from the slab
and elevate the home, leaving the slab foundation in place. After
the home is lifted, a new, elevated floor is constructed.
Unlike other types of construction in which elevation can be
relatively straightforward, elevating slab-on-grade homes with
the slab intact is technically challenging and often not feasible.
When a slab-on-grade home is elevated with the slab intact, the
slab, which was previously continuously supported by the soils
beneath it, must function as a structural element. It must span
the distance between the portions of the foundation that sup-
port the elevated home. Typically, these slabs often are either
unreinforced or only lightly reinforced with welded wire fabric
and are essentially non-structural. These slabs may not be able
to support the loads of an elevated home. Consequently, the slab
foundation should be thoroughly evaluated by a registered de-
sign professional before choosing this mitigation option.
Alternative techniques are available for masonry homes on slab-
on-grade foundations. As described later in this section, these
techniques do not require the lifting of the home. Instead, they
involve raising the floor within the home or moving the living
space to an upper story. Guidance for elevating slab-on-grade
masonry homes can be found in FEMA P-347, Above the Flood: El-
evating Your Floodprone House (FEMA. 2000).
Although elevating a home can help protect it from floodwaters,
you need to consider other hazards before choosing this meth-
od. Elevating the home can make it more susceptible to damage
from earthquakes. In addition, both continuous wall founda-
tions and open foundations can fail as a result of damage caused
by erosion and the impact of debris carried by floodwaters. If
portions of the original foundation, such as the footings, are
used to support new walls or other foundation members, or a
new second story, they must be capable of safely carrying the
additional loads imposed by the new construction and the ex-
pected flood, wind, and earthquake forces.
Method #1: Elevating on Continuous Foundation Walls
Although this method is usually used in flood hazard areas
where the risks of wave action and high-velocity flow are low
(Figures 3-6 and 3-7), continuous foundation walls in low-velocity flow areas with wave action can also be sus-
ceptible to structural damage. Open foundations should be considered as a reasonable mitigation option. After
the home is detached from its foundation and raised on jacks, the existing foundation is often saved and the
DEFINITION
A footing is the base of a foundation.
Footings are usually made of con-
crete and may be reinforced with steel
bars. Foundation walls are support-
ed on continuous footings; separate
foundation members, such as piers,
are supported on individual footings.
CROSS REFERENCE
FEMA has produced a videotape
titled Best Build 3: Protecting a
Flood-Prone Home, which illustrates
the retrofitting methods described in
this guide (see Appendix A).
NOTE
Elevation on open foundations is re-
quired by the NFIP in Zone V areas
(even when the ground elevation lies
above the BFE) and is strongly rec-
ommended for Coastal A Zones.
Some States and communities have
formally adopted open foundation
requirements for Coastal A Zone
construction.
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foundation walls are extended. The new portions of the walls are usually made of masonry block or cast-in-place
concrete. Although this method may be the easiest way to elevate a home, it can involve some additional construc-
tion modifications or reinforcements.
Figure 3-6. Typical cross-
section of home elevated on
continuous foundation walls.
Figure 3-7. Before (left) and after (right) photos of a retrofitted home elevated on extended continuous foundation walls.
Depending on the size of your home, the amount of elevation, and the magnitude of the potential environmental
loads (such as those from floods, wind, earthquakes, and snow), your contractor may have to modify or reinforce
the footings and foundation walls to ensure the structural stability of the home. The original footings may have to
be replaced with ones that have a higher capacity for environmental loads. Both the footings and the foundation
walls may need to be reinforced with steel bars.
This type of foundation creates what is referred to under the NFIP as an “enclosure.” The enclosure must be con-
structed of flood damage-resistant materials, have all service equipment elevated above the DFE, and be used only
for parking, access, or storage. NFIP Technical Bulletin 2, Flood Damage-Resistant Materials Requirements (FEMA. 2008),
defines a “flood [damage]-resistant material” as “any building product [material, component, or system] ca-
pable of withstanding direct and prolonged contact with floodwaters without sustaining significant damage.”
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AN OVERVIEW OF THE RETROFITTING METHODS 3
“Prolonged contact” means at least 72 hours, and “significant damage” means any damage requiring more than
cosmetic repair. Technical Bulletin 2 provides a detailed list of appropriate flood damage-resistant materials and
also classifies flood damage-resistance of materials as acceptable or unacceptable based on water resistance and
ability to be cleaned.
The enclosure must also be constructed with openings to allow equalization of hydrostatic pressure to comply
with NFIP and building code requirements. As explained in Chapter 2, unequalized hydrostatic pressure exerted
by floodwaters can collapse walls, regardless of the construction materials used. The NFIP may require that open-
ings be installed in the foundation walls so that water can flow into and out of any enclosed area below the newly
elevated home. NFIP Technical Bulletin 1, Openings in Foundation Walls and Walls of Enclosures (FEMA. 2008), provides
guidance on the NFIP regulations concerning openings in foundation walls. When the water levels on both sides
of the foundation walls are the same, the hydrostatic pressure is equalized. If you are elevating your home as part
of a Substantial Improvement or in connection with repairs of Substantial Damage, your community’s floodplain
management ordinance, regulation, or provisions of the building code will require that you install openings in all
areas below the BFE. Consult your local officials about local requirements for openings.
Method #2: Elevating on Open Foundations
Unlike continuous foundations, open foundations consist of individual vertical structural members that support
the home only at key points. Because they present less of an obstacle to flood flows than continuous walls, open
foundations can be used in areas where there are risks of wave action and high-velocity flood. Most open founda-
tions consist of piers, posts, columns, or piles.
Piers. Piers (or columns) are commonly built with
masonry block or are made of cast-in-place concrete
(Figure 3-8). Piers can be made from wood and steel as
well. The bottom of each pier sits on a concrete footing.
Pier foundations are used in conventional construction;
they are not just a means of elevating a flood-prone
home. In conventional use, they are designed primarily
for vertical loading—to hold the weight of the home.
They are not normally designed to resist large horizontal
forces, such as those associated with moving floodwa-
ters, waves, impacts from floodborne debris, wind, and
earthquakes. As a result, pier foundations are generally
used where the risks of wave action and high-velocity
flow are low to moderate and the potential for earth-
quakes is low.
If you decide to elevate your home on a pier foundation,
you should expect your contractor to reinforce the piers
and footings with steel reinforcing bars and to connect
the piers to the footings so they will not separate under
flood or other forces. Adequate connections between the
piers and the home are also necessary so that the home
and foundation will resist lateral loads from floods,
winds, and earthquakes, and uplift from buoyancy.
Figure 3-8. Home elevated on reinforced concrete piers.
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Posts. Posts are usually made of wood or steel (Figure
3-9). They are generally square but may also be round.
Posts are set in holes, and their ends are encased in con-
crete, or supported on concrete pads (as in the figure).
After posts are set, the holes are filled with concrete, dirt,
gravel, or crushed stone.
Posts can be connected to each other with bracing made
of wood, steel rods, or guy wires. The type is usually de-
termined by cost, flood conditions, expected loads, the
availability of materials, and local construction practice.
Like piers, posts are generally used where the risks of
wave action and high-velocity flow are low to moderate.
One primary difference between piers, and posts is the
dimension of the element – piers are larger in cross sec-
tion because they usually are CMU (concrete masonry
unit) or concrete block and are usually shorter than
posts. Posts are braced together because they are usu-
ally taller and more slender with less stability than piers.
Piles. Piles are usually made of wood, but fiber-reinforced poly-
mer, steel, or precast concrete piles are also common in some
areas (Figure 3-10). Piles are similar to posts but, instead of be-
ing set in holes, they are driven into the ground or jetted in with
streams of water. Also, piles are embedded deeper in the ground
than either piers or posts. As a result, pile foundations are less
susceptible to the effects of high-velocity flow, waves, debris
impact, erosion, and scour than the other types of open founda-
tions. Piles differ from piers and posts also in that they do not
rest on footings. Instead they are driven until they rest on a solid
support layer, such as bedrock, or until they are embedded deep
enough that the friction between the ground and the piles will
enable them to resist the loads that are expected to act on them.
Because driving and jetting piles requires bulky, heavy construc-
tion machinery, an existing home must normally be moved off
its existing foundation and set on cribbing until the operation
is complete. As a result, elevating a home by placing it on a pile
foundation will usually require more space and cost more than
elevating with another type of foundation. Pile foundations are used primarily in areas where other elevation
methods are not feasible, such as where floodwaters are deep and the risks of wave action and high-velocity flow
are great. For example, pile foundations are used extensively in oceanfront areas exposed to high-velocity flow,
waves, and high winds (Figure 3-11).
Figure 3-9. Home elevated on posts
DEFINITION
Concrete materials such as posts,
beams, and blocks that are brought to
the construction site in finished form
are referred to as precast.
Jetting is a process in which the hole
for the installation of a pile is made by
a high-pressure stream of water from
a nozzle attached to the bottom of the
pile.
Cribbing usually consists of a frame-
work of crisscrossed timbers that
provides temporary structural support.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-17
AN OVERVIEW OF THE RETROFITTING METHODS 3
Figure 3-10. Home elevated on piles.
Figure 3-11. Example of
well-elevated and embedded
pile foundation tested by
Hurricane Katrina. Note
adjacent building failures
(Dauphin Island, AL, 2005).
3-18 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
3 AN OVERVIEW OF THE RETROFITTING METHODS
Methods #3 and #4: Elevating by Extending the Walls of the Home or Moving the Living Space to
an Upper Floor
For masonry homes on slab-on-grade foundations, two alterna-
tive elevation methods are available. One is to remove the roof,
extend the walls of the home upward, replace the roof, and
build a new, raised floor at the DFE (Figure 3-12). This tech-
nique works best where the floor needs to be raised less than
4 feet to reach the DFE. The floor can be either a new slab or a
new wood-framed floor. For a new slab, fill dirt is placed on top
of the old slab and the new slab is built on top. If a new wood-
framed floor is built, the space between it and the old slab is left
open and becomes a crawlspace (and must be retrofitted with
openings to allow floodwaters in the crawlspace).
CROSS REFERENCE
As discussed in Section 2.6, the cost
of elevating a Substantially Damaged
home may be eligible for a flood insur-
ance claim under ICC coverage.
Figure 3-12. The owner of
this flood-prone home in
south Florida decided to build
a new wood-framed second
story on top of the masonry
first story. The new second
story is well above the BFE.
The second technique is to abandon the entire lower floor, or lower enclosed area, of the home and move the
living space to an existing or newly constructed upper story. This technique works best for multi-story homes
where the DFE is more than 4 feet above the level of the lower floor. The abandoned lower floor or enclosed area
is then used only for parking, building access, or storage.
These techniques, like the others, have their limitations. The portions of the home below the DFE will be exposed
to flooding and must, therefore, be made of flood damage-resistant materials. That is why this method is appli-
cable to masonry homes rather than frame homes, which would be much more easily damaged by flooding. The
area below the DFE cannot be used for living space; it may be used only for parking, building access, or storage. In
addition, all appliances and utilities must be moved to the upper floor. Also, openings must be cut into the walls
of the lower floor to allow water to enter during flooding so that the hydrostatic pressure on the walls will be
equalized. In essence, the lower floor is wet floodproofed (see Section 3.4.1).
Adding a new second story to a single-story home may require that the foundation be strengthened so that it can
support the additional load. You must consult an engineer if you plan to use this method. The second story can be
frame or masonry (to match the lower floor). The method you choose will depend on the advice of your engineer,
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-19
AN OVERVIEW OF THE RETROFITTING METHODS 3
cost, appearance, the availability of materials and experienced contractors, and the risks of other natural hazards
such as hurricanes and earthquakes.
Table 3-1 presents the advantages and disadvantages of elevation.
The relative costs shown in Table 3-2 are for elevating frame, masonry veneer, and masonry homes of various
foundation types. The costs for extending utilities and adding or extending staircases are included. The costs
shown for elevating frame, masonry veneer, and masonry homes on existing slab-on-grade foundations are based
on the assumption that the home is raised with the existing slab attached.
Table 3-1. Advantages and Disadvantages of Elevation
Advantages Disadvantages
• Brings a Substantially Damaged or Improved building
into compliance with the NFIP if the lowest horizontal
structural member of the lowest floor is elevated to the
BFE
• Reduces flood risk to the structure and its contents
• Eliminates the need to relocate vulnerable items
above the flood level during flooding
• Often reduces flood insurance premiums
• Uses established techniques
• Can be initiated quickly because qualified contractors
are often readily available (unless project is imple-
mented immediately after a disaster)
• Reduces the physical, financial, and emotional strains
that accompany flood events
• Does not require the additional land that may be
needed for floodwalls or levees
• May be cost-prohibitive
• May adversely affect the structure’s appearance
• May adversely affect access to the structure
• Cannot be used in areas with high-velocity water flow,
fast-moving ice or debris flow, or erosion, unless spe-
cial measures are taken
• May require additional costs to bring the structure up
to current building codes for plumbing, electrical, and
energy systems
• Requires consideration of forces from wind and seis-
mic hazards and possible changes to building design
NFIP = National Flood Insurance Program; BFE = base flood elevation
3-20 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
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Table 3-2. Relative Costs of Elevating a Home
Construction Type Existing Foundation Retrofit Relative Cost
Frame
Basement, crawlspace,
or open foundation
Elevate on continuous foundation walls or
open foundation Lowest
Highest
Frame with masonry veneer Elevate on continuous foundation walls or
open foundation
Load bearing masonry Extend existing walls and create new
elevated living area
Frame
Slab-on-grade
Elevate on continuous foundation walls or
open foundation
Frame with masonry veneer Elevate on continuous foundation walls or
open foundation
Load bearing masonry Elevate on continuous foundation walls or
open foundation
Occasionally, slab-on-grade homes are raised without the slab.
Although this method can be less expensive than raising the
home with the slab, it involves detaching the home from the
slab and requires extensive alterations to interior and exterior
walls.
The cost of abandoning an existing lower level will depend on
whether the home already has an upper level that can be used
for living space. If an upper level is available, abandoning the
lower floor would involve primarily elevating or relocating util-
ities, adding openings in the lower-level walls, and ensuring
that all construction materials below the BFE are flood damage
resistant. This method is well-suited to a home with a walkout-
on-grade basement, which can be wet floodproofed and used
for parking, building access, or storage. The cost of adding a
new frame upper level and raising the roof to accommodate the
new level would vary, depending upon the amount of interior
finishing and other factors.
3.3.2 Relocation and Demolition
Relocation is the retrofitting measure that can offer the greatest security from future flooding. It involves mov-
ing an entire structure to another location, usually outside the floodplain. Relocation as a retrofitting measure not
only relieves anxiety about future flooding, but also offers the opportunity to reduce future flood insurance pre-
miums. Demolition is tearing down a damaged home. A new compliant home can be rebuilt on site, rebuilt on
another property, or the owner can simply move in to another structure elsewhere. These retrofitting methods are
discussed below.
DEFINITION
The footprint of a house is the land
area it covers (see figure). This area
is equal to the length of the house
multiplied by its width. Note that the
footprint is not necessarily equal to
the total square footage of the house.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-21
AN OVERVIEW OF THE RETROFITTING METHODS 3
Relocation
Moving your home to high ground, outside the flood hazard area, is the most effective of the ret-
rofitting methods described in this guide. Retrofitting literature commonly refers to this method as
relocation. Chapter 6 presents more detailed information on relocation. When there is enough space
and the ground is high enough, you may even be able to move your home to another location on the
same piece of property.
Relocating a home involves detaching it from the foundation, raising it with jacks, and placing it on a wheeled
vehicle that delivers it to the new site. The original foundation is demolished and a new foundation is built at the
new site. The home is installed on the new foundation and all utility lines are connected. Relocation is particularly
appropriate in areas where the flood hazard is severe, such as where flood conditions are characterized by one or
more of the following:
n Deep water
n Rapid rates of rise and fall
n Short warning time
n Wave action
n High-velocity flow
n High debris potential
n Long duration
n Erosion
Relocation is also appropriate for homeowners who want to be free of worries about damage from future floods
that may exceed a selected flood protection elevation.
Although similar to elevation, relocation requires additional steps that usually make it more expensive. These in-
clude moving the home, buying and preparing a new site (including building the new foundation and providing
the necessary utilities), and restoring the old site (including demolishing the old foundation and capping and
abandoning old utility lines).
Homes of all sizes and types can be relocated, either as a unit or in segments. One-story frame homes are usually
the easiest to move, particularly if they are built on a crawlspace or basement foundation that provides easy access
to the floor framing. Masonry homes can also be moved, but usually with more difficulty and at a higher cost.
Professional home movers can advise you about the things you need to consider when deciding whether to re-
locate. The structural integrity of your home will have to be checked. Also, you may need to find a place where
you can store furniture and other belongings temporarily. However, in most instances, the contents of your home
may remain in the home while it is being moved. Keep in mind that there must be a clear route to the new site.
Narrow roads, restrictive overpasses, and bridges with low weight limits may make it impossible for your home
to be moved to the new site. Also, many States and communities have requirements that govern the transport of
homes and other buildings on public rights-of-way. For information about structural movers in your area, visit
http://www.iasm.org. Table 3-3 presents the advantages and disadvantages of relocation.
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Table 3-3. Advantages and Disadvantages of Relocation
Advantages Disadvantages
• Allows Substantially Damaged or Improved structure
to be brought into compliance with the NFIP
• Significantly reduces flood risk to the structure and its
contents
• Uses established techniques
• Can be initiated quickly because qualified contractors
are often readily available (unless project is imple-
mented immediately after a disaster)
• Can eliminate the need to purchase flood insurance or
reduce the premium because the home is no longer in
the floodplain
• Reduces the physical, financial, and emotional strains
that accompany flood events
• May be cost-prohibitive
• Requires locating a new site
• Requires addressing disposition of the flood-prone
site
• May require additional costs to bring the structure up
to current building codes for plumbing, electrical, and
energy systems
• May take a long time, depending on time required to
find desired property, purchase it, and develop it with
desired utilities
• May be cost-prohibitive to relocate, as well as to de-
velop the site with desired utilities (water, sewage,
electrical, natural gas, cable, telephone etc.)
NFIP = National Flood Insurance Program
Table 3-4 shows the relative costs of relocating homes of differ-
ent construction and foundation types. In addition to moving
and construction costs, it is important to account for the addi-
tional relocation project costs of any new property that must be
purchased.
Table 3-4. Relative Costs of Relocation
Construction Type Existing Foundation Retrofit Relative Cost
Frame
Crawlspace, or open
foundation
Relocate existing home and install the
home on a new foundation at the new
site, hook up utilities, and restore the old
site
Lowest
Highest
Frame with masonry veneer
Load bearing masonry
Frame
BasementFrame with masonry veneer
Load bearing masonry
Frame
Slab-on-gradeFrame with masonry veneer
Load bearing masonry
WARNING
The relative relocation costs shown
here are based on a small home.
Because relocation costs do not in-
crease proportionally with the size of
a home, the cost per square foot of
moving a larger home may be less
than that shown here.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-23
AN OVERVIEW OF THE RETROFITTING METHODS 3
Demolition
Demolition is tearing down a damaged home. A new compliant home can be rebuilt on site, rebuilt
on another property, or the owner can simply move in to another structure elsewhere. This retrofitting
method may be the most practical of all those described in this guide when a home has sustained ex-
tensive damage, especially severe structural damage. Chapter 6 presents more detailed information on
demolition.
Whether you intend to rebuild or move, you must tear down
your damaged home and then restore the site. Site restoration
usually involves filling in a basement, grading, and landscap-
ing. As a result, you will need the services of a demolition
contractor. The contractor will disconnect and cap all utility
lines at the site and then raze the home with a bulldozer or
other heavy equipment. If you decide to rebuild on the old
site or somewhere else on the same property, your construc-
tion contractor may be able to do the demolition and site
restoration work as part of the home construction.
Remember, all demolition, construction, and site restoration work must be done according to the regulatory re-
quirements of your community. Permits may be required for all or part of this work. If you decide to rebuild on
the site of your old home, you must rebuild in compliance with your community’s floodplain management or-
dinance or law and other ordinances and codes, which means ensuring that the lowest floor of your new home
is at or above the DFE. You can do this by elevating your new home on an extended foundation as described in
Section 3.3.1 or on compacted fill dirt if your property is located in Zone A. If your property is located in Zone V
area, you must elevate your home on piles or columns. A better approach is to build your home on an alternative
building site outside the regulatory floodplain, where you can use standard construction practices, including the
construction of a basement. Remember, if you rebuild on the same site, within the regulatory floodplain, your
community’s floodplain management ordinance, regulation, or provisions of the building code will not allow
your new home to have a basement (as defined by the NFIP regulations) if it is located below the DFE. Figure 3-13
shows a home damaged by Hurricane Irene that is slated for demolition.
Figure 3 13. Many homes in
the Town of Prattsville, NY,
were slated for demolition
during the recovery effort
following Hurricane Irene.
CROSS REFERENCE
As discussed in Section 2.6, the
cost of demolishing a Substantially
Damaged home may be an eligi-
ble flood insurance claim under ICC
coverage.
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3 AN OVERVIEW OF THE RETROFITTING METHODS
The advantages and disadvantages of demolition vary depend-
ing on which of the following three options you choose:
1. Rebuilding on the existing site
2. Rebuilding on an alternative site on a different part of
your property, which may be outside the regulatory
floodplain
3. Moving to a home on another property, which may be
outside the regulatory floodplain
The advantages and disadvantages of option 1 are similar to those listed in Table 3-1 for the elevation method.
The advantages and disadvantages of options 2 and 3 are the same as those listed in Table 3-3 for the relocation
method, with the following exceptions: If you choose option 2, you will avoid the need to buy another lot and
dispose of your existing property.
If you decide to demolish your damaged home and rebuild somewhere on your existing property (option 1 or
2 above), your costs will include tearing down the damaged home, building the new home to the community’s
specified elevation, reconnecting utility lines, and restoring the site around the new home. If you decide to move
to a home outside the regulatory floodplain (option 3), your costs will include tearing down the damaged home,
buying or building a home elsewhere, capping and abandoning the old utility lines, and restoring the old site.
The cost of tearing a home down, which is not a complex or difficult job, will be almost entirely for the disposal
of the resulting debris. This cost can vary widely, depending on the amount of debris and whether a dumping fee
is required at the disposal site. The major costs associated with the demolition method will be for building or buy-
ing a home and will, therefore, depend on how and where you build or on the type of home you buy. Be sure to
get a complete cost estimate before you begin a demolition project. Table 3-5 shows approximate costs for tearing
down your home and rebuilding on the same site.
Table 3-5. Relative Costs of Demolition and Rebuilding
Construction Type Proposed Foundation Type Relative Cost
Frame Closed Foundation Lowest
Highest
Open Foundation
Frame with Masonry Veneer Closed Foundation
Open Foundation
Load bearing masonry Closed Foundation
Open Foundation
CROSS REFERENCE
See Section 7.1.7 for a discussion of
flood damage-resistant materials.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-25
AN OVERVIEW OF THE RETROFITTING METHODS 3
3.4 Floodproofing
Wet floodproofing allows floodwaters to enter your home while using various techniques to minimize flood dam-
age and protect critical systems and contents. Wet floodproofing techniques include raising utilities and important
contents to or above the flood protection level, installing and configuring electrical and mechanical systems to
minimize disruptions and facilitate repairs, installing flood openings or other methods to equalize the hydrostatic
pressure exerted by floodwaters, and installing pumps to gradually remove floodwater from basement areas after
the flood.
The purpose of dry floodproofing your home is to make it watertight (substantially impermeable) to floods of
limited duration (a few hours) and depth (typically less than 2-3 feet). Dry floodproofing reduces the potential
for flood damage by reducing the probability that your home’s interior will be inundated. It can be an appropriate
alternative for flood mitigation when relocating or elevating buildings is not cost effective or technically feasible.
3.4.1 Wet Floodproofing
Wet floodproofing a home is modifying the uninhabited portions of the home (such as a crawlspace,
basement, or other enclosure) so that floodwaters will enter but not cause significant damage to ei-
ther the home or its contents. The purpose of allowing water into portions of the home is to ensure
that the interior and exterior hydrostatic pressures will be equal. Allowing these pressures to equalize
greatly reduces the likelihood of wall failures and structural damage. Wet floodproofing may be used when other
retrofitting methods are either too costly or are not feasible. If you intend to wet floodproof your basement, a
licensed engineer or design professional is needed to determine the structural integrity of the walls. Wet flood-
proofing is practical in only a limited number of situations. Chapter 7 presents more detailed information on wet
floodproofing.
Because wet floodproofing allows floodwaters to enter the
home, all construction and finishing materials below the DFE
should be resistant to flood damage. For this reason, wet flood-
proofing is practical only for portions of a home that are not
used for living space, such as a basement as defined by the NFIP
regulations, an enclosure such as a walkout-on-grade basement
or a crawlspace, or an attached garage. Figure 3-14 illustrates a
home with a wet floodproofed subgrade basement. Wet flood-
proofing this home protects it from hydrostatic pressure, but
not hydrodynamic pressure and floodborne debris. To minimize
damages, service equipment must be elevated above the flood
level and the walls of the basement must be built with flood
damage-resistant materials.
Figure 3-15 illustrates a home in which the lower level was
modified to create an enclosure that is built with flood damage-
resistant materials, service equipment was elevated above the
flood level, and the lower level is used solely for parking, access,
and storage. As illustrated in Figure 3-15, openings must be
placed in the walls to relieve hydrostatic pressure. If the lowest
elevated floor is above the community’s DFE and the enclosure
is protected as described above, the home would meet the mini-
mum requirements of the NFIP.
WARNING
Wet floodproofing mitigation methods
can lead to NFIP compliance only if
the area is limited to parking, access,
or storage; designed to allow for au-
tomatic entry and exit of flood waters;
and uses only flood damage-resis-
tant materials below the DFE. If your
home is being Substantially Improved
or has been Substantially Damaged,
your community’s floodplain man-
agement ordinance or law will restrict
your use of wet floodproofing to at-
tached garages and enclosed areas
below the BFE that are used solely for
parking, building access, or storage.
For more information, consult your
local officials. Note that basements
(any area of the building having its
floor subgrade on all sides) cannot
be wet floodproofed to meet NFIP
requirements.
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Wet floodproofing would not be practical for most slab-on-grade homes in which the living space is at or very
near the ground level. Whether or not wet floodproofing is appropriate for your home will depend on the flood
conditions, the flood protection elevation you have selected, the design and construction of your home, and
whether you are required to bring your home into compliance because it is being Substantially Improved or has
been Substantially Damaged.
Figure 3-14. A home with a
wet floodproofed subgrade
basement. Note: Wet
floodproofing a basement is
not permitted to achieve NFIP
compliance. If Substantial
Improvement or Substantial
Damage requirements are
triggered, the basement
would need to be filled.
WARNING
After floodwaters recede from around a home with a wet flood-
proofed basement, you will need to pump out the water that
filled the basement during the flood. However, you must take
certain precautions before you pump out the water. If the soil
surrounding the basement walls and below the basement
floor is still saturated with water, removing the water in the
basement too quickly can be dangerous. As the water level in
the basement drops, the outside pressure on the basement
walls and floor becomes greater than the inside pressure (see
figure). As a result, the walls can collapse and the floor can be
pushed up or cracked (see Section 2.3.1). If you are unsure
whether pumping out your basement is safe, contact a li-
censed dewatering contractor. Note that basements (any area
of the building having its floor subgrade on all sides) cannot
be wet floodproofed to meet NFIP requirements.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-27
AN OVERVIEW OF THE RETROFITTING METHODS 3
Figure 3-15. A home with a
wet floodproofed enclosure.
Note: Interior grade must be
at or above the exterior grade
along the entire length of the
lowest side to prevent being a
basement.
If you are considering wet floodproofing, keep the following in mind:
n Your home should have space above the DFE in which you can temporarily or permanently store items
that could be damaged by floodwaters.
n If your furnace, water heater, or other service equipment is below the DFE, it should be protected as well.
You may be able to move the equipment to another floor, elevate it, or protect it in place (see Chapter 9).
n Any construction and finishing materials below the DFE that are not flood damage-resistant should be
removed or replaced with materials that are flood damage-resistant.
n If a flood occurs, you will not be able to live in your home as long as floodwaters remain.
n Wet floodproofing does not alleviate the threat of damage from high-velocity flood flow and wave action.
n Your community’s floodplain management ordinance, regulation, or provisions of the building code
will not allow you to wet floodproof your basement as defined under the NFIP if your home has been
Substantially Damaged or is being Substantially Improved.
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Table 3-6. Advantages and Disadvantages of Wet Floodproofing
Advantages Disadvantages
• Reduces the risk of flood damage to a building and its
contents, even with minor mitigation
• Greatly reduces loads on walls and floors due to
equalized hydrostatic pressure
• May be eligible for flood insurance coverage of cost of
relocating or storing contents, except basement con-
tents, after a flood warning is issued
• Costs less than other measures
• Does not require extra land
• Reduces the physical, financial, and emotional strains
that accompany flood events
• Does not satisfy the NFIP requirement for bringing
Substantially Damaged or Improved structures into
compliance
• Usually requires a flood warning to prepare the build-
ing and contents for flooding
• Requires human intervention to evacuate contents
from the flood-prone area
• Results in a structure that is wet on the inside and
possibly contaminated by sewage, chemicals, and
other materials borne by floodwaters and may require
extensive cleanup
• Does not eliminate the need to evacuate during floods
• May make the structure uninhabitable for some period
after flooding
• Limits the use of the floodable area
• May require ongoing maintenance
• May require additional costs to bring the structure up
to current building codes for plumbing, electrical, and
energy systems
• Requires care when pumping out basements to avoid
foundation wall collapse
NFIP = National Flood Insurance Program
Wet floodproofing is generally less expensive than the
other flood protection methods described in this guide. Table
3-7 shows the relative approximate costs of wet floodproofing
homes on basement and crawlspace foundations to heights be-
tween 2 feet and 8 feet. In a home with a basement, this height is
measured from the basement floor. In a home with a crawlspace,
this height is measured from the lowest adjacent grade to the
home. The relative costs include those for adding wall open-
ings for the entry and exit of floodwaters, installing pumps,
rearranging or relocating utility systems, moving large appliances, and making it easier to clean up after flood-
waters recede. The relative costs shown for basements in Table 3-7 are valid only for unfinished basements.
Wet floodproofing a finished basement would involve the removal of all non-flood damage-resistant materi-
als and replacing finish materials with flood damage-resistant materials. As a result, wet floodproofing costs for
finished basements would be higher and would vary, depending on the amount of finish material to be removed
or replaced.
DEFINITION
The lowest adjacent grade is the
lowest ground surface that touches
any of the exterior walls of your home.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-29
AN OVERVIEW OF THE RETROFITTING METHODS 3
Table 3-7. Relative Costs of Wet Floodproofing
Construction Type Existing Foundation Retrofit Relative Cost
Frame, frame with
masonry veneer, or load
bearing masonry
Crawlspace Wet floodproof crawlspace to a height of 2 ft
to 4 ft above LAG*Lowest
Highest
Basement Wet floodproof unfinished basement to a
height of 2 ft to 4 ft above the basement floor
Basement Wet floodproof unfinished basement to a
height of 8 ft above the basement floor
* LAG – Lowest Adjacent Grade
3.4.2 Dry Floodproofing
In some situations, a home can be made watertight
below the DFE, so that floodwaters cannot enter. This
method is called “dry floodproofing.” Section 7.2
presents more detailed information on dry flood-
proofing. Making the home watertight requires sealing the walls
with waterproof coatings, impermeable membranes, or supple-
mental layers of masonry or concrete. Also, doors, windows, and
other openings below the DFE must be equipped with perma-
nent or removable shields, and backflow valves must be installed
in sewer lines and drains.
The flood characteristics that determine whether dry flood-
proofing is effective are flood duration, flow velocity, and the
potential for wave action and floodborne debris. You should
consult a design professional before undertaking a dry flood-
proofing project. Figure 3-16 shows a typical dry floodproofed
home and Table 3-8 presents the advantages and disadvantages
of dry floodproofing.
Flood protection elevation is important to know because of the
hydrostatic pressure that floodwaters exert on walls and floors.
Because water is prevented from entering a dry floodproofed
home, the exterior pressure on walls and floors is not counter-
acted as it is in a wet floodproofed home (see the discussion on
pages 3-26 and 3-27). The ability of a home’s walls to withstand
the pressure exerted by floodwaters depends partly on how the
walls are constructed. Typical frame and masonry veneer walls
are likely to fail at lower flood depths, are more difficult to make
WARNING
Dry floodproofing may not be used
to bring a Substantially Improved or
Substantially Damaged home into
compliance with your community’s
floodplain management ordinance
or law unless the home is located in
a community granted with a flood-
proofing exception.1 Dry floodproofing
residential buildings will not reduce
flood insurance premiums.
WARNING
Even concrete block and brick walls
should not be dry floodproofed above
a height of 3 feet, unless an engineer-
ing analysis has been performed that
shows that the walls will withstand the
expected hydrostatic and hydrody-
namic loads and debris impact forces.
The effects of buoyancy on slab floors
must also be considered.
1 Use FEMA Form 086-0-24, Residential Basement Floodproofing Certificate: This is a form that is provided to communities participating
in the National Flood Insurance Program that have been granted an exception by FEMA to allow the construction of floodproofed
residential basements in Special Flood Hazard Areas.
3-30 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
3 AN OVERVIEW OF THE RETROFITTING METHODS
watertight, and are more vulnerable to damage from moisture.
As a result, dry floodproofing is not recommended for homes
with frame and masonry veneer walls.
Even if frame and masonry veneer walls are reinforced to with-
stand the pressure of deeper water, the effects of buoyancy must
be considered. The buoyancy force exerted by water may be
enough to crack a slab floor or push it up.
Figure 3-16. A typical dry
floodproofed home.
WARNING
Because dry floodproofing requires
human intervention, you must be will-
ing and able to install all flood shields
and carry out all other activities re-
quired for the successful operation of
the dry floodproofing system. As a re-
sult, not only must you be physically
capable of carrying out these activi-
ties, you must be home or able to get
home in time to do so before floodwa-
ters arrive.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-31
AN OVERVIEW OF THE RETROFITTING METHODS 3
Table 3-8. Advantages and Disadvantages of Dry Floodproofing
Advantages Disadvantages
• Reduces the flood risk to the structure and contents if
the design flood level is not exceeded
• May be less costly than other retrofitting measures
• Does not require the extra land that may be needed
for floodwalls or reduced levees
• Reduces the physical, financial, and emotional strains
that accompany flood events
• Retains the structure in its present environment
and may avoid significant changes in appearance
• Does not satisfy the NFIP requirement for bringing
Substantially Damaged or Improved residential struc-
tures into compliance
• Requires ongoing maintenance
• Does not reduce flood insurance premiums for resi-
dential structures
• Usually requires human intervention and adequate
warning time for installation of protective measures
• May not provide protection if measures fail or the flood
event exceeds the design parameters of the measure
• May result in more damage than flooding if design
loads are exceeded, walls collapse, floors buckle, or
the building floats
• Does not eliminate the need to evacuate during floods
• May adversely affect the appearance of the building if
shields are not aesthetically pleasing
• May not reduce damage to the exterior of the building
and other property
• May lead to damage of the building and its contents if
the sealant system leaks
• Involves increased costs for a design professional
• At times, may require invasive retrofits
• Does not minimize the potential for damage from
high-velocity flood flow and wave action
NFIP = National Flood Insurance Program
Duration of flooding is critical because most sealing systems will begin to allow some seepage after prolonged
periods of exposure to water. If your home is in an area where floodwaters remain high for 24 hours or longer,
you should use a different retrofitting method. Dry floodproofing is not appropriate in areas with a risk of high-
velocity flood flow, wave action, or both. Either condition may render dry floodproofing totally ineffective and
cause severe damage.
Floodproofed homes are not meant to be occupied during a flood. Flood warning time should be adequate and
evacuation plans should be developed to ensure that occupants are not stranded in the home during a flood. Dry
floodproofing actually increases the risk to occupants if floodwaters rise higher than the floodproofing design
level because severe structural damage can occur. Further, the interior of the home will likely be subject to inun-
dation, which may occur rapidly.
3-32 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
3 AN OVERVIEW OF THE RETROFITTING METHODS
Dry floodproofing is not recommended for homes with basements. Saturated soils pressing against basement walls
can damage them or cause them to fail. The buoyancy force exerted by saturated soils below the basement can
cause the basement floor to fail or even push the entire home up.
Sealant systems, especially those that rely on membranes and coatings, can be punctured by ice and other types
of debris. If your home is in an area where floodwaters are known to carry debris, you should select a different
retrofitting method.
The total cost for dry floodproofing a home will depend largely on the size of the home, the type and condition
of the wall system, the flood protection elevation, types of sealant and shield materials used, number of plumbing
lines that have to be protected by check valves, and number of openings that have to be covered by shields. Table
3-9 shows approximate costs for elements of a dry floodproofing project.
Table 3-9. Relative Costs of Dry Floodproofing
Component Height of Dry Floodproofing Relative Cost
Waterproof Membrane (above grade)1
3 Feet
Lowest
Highest
Asphalt (two coats on foundation up to 2 feet below grade)1
Sprayed-on Cement (above grade)1
Wood Flood Shield Lowest
Highest
Metal Flood Shield
1 Cement, asphalt, and membrane are alternative sealant methods.
3.4.3 Barrier Systems
Levees and floodwalls are types of flood protection barriers. A levee is a compacted earthen structure; a
floodwall is an engineered structure usually built of concrete, masonry, or a combination of both (con-
crete masonry unit [CMU]). When these barriers are built to protect a home, they are usually referred
to as “residential,” “individual,” or “onsite” levees and floodwalls. The practical heights of these levees
and floodwalls are usually limited to 6 feet and 4 feet, respec-
tively. These limits are the result of the following considerations:
n As the height of a levee or floodwall increases, so does
the depth of water that can build up behind it. Greater
depths result in greater water pressures, so taller levees
and floodwalls must be designed and constructed to
withstand the increased pressures. Meeting this need
for additional strength greatly increases the cost of the
levee or floodwall, usually beyond what an individual
homeowner can afford.
WARNING
Levees and floodwalls may not be
used to bring a Substantially Improved
or Substantially Damaged home into
compliance with your community’s
floodplain management ordinance or
law and do not eliminate the insur-
ance requirement on the home for
federally backed mortgages.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-33
AN OVERVIEW OF THE RETROFITTING METHODS 3
n Because taller levees and floodwalls must be stronger, they usually require more space than is likely to be
available on an individual lot. This is especially true of levees.
n Levees require a large land area for construction. For example, the levee in Figure 3-20 is 4 feet tall and
about 27 feet wide.
Chapter 8 presents more detailed information on levees and floodwalls. Figure 3-17 shows a home protected by a
levee and floodwall; Figure 3-18 shows a home protected by a levee. Remember that levees and floodwalls should
be designed by a licensed engineer.
Figure 3-17. A home
protected by a levee (left)
and a floodwall (right).
Figure 3-18. A home
protected by a levee.
3-34 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
3 AN OVERVIEW OF THE RETROFITTING METHODS
Both levees and floodwalls should provide at least 1 foot of freeboard. For example, if you are building a levee to
protect your home from the base flood, the top of the levee should be at least 1 foot above the BFE.
For a levee to be effective over time, it must be constructed of
soils that cannot be easily penetrated by floodwaters, it must
have proper side slopes for stability, and it must be periodically
inspected and maintained. In areas where high-velocity flows
could erode the surface of a levee, the side of the levee exposed
to floodwater is usually protected with a covering of rock, re-
ferred to as riprap, or with other erosion-resistant material.
Levees can surround a home, or they may be built only across
low areas and tied into existing high ground.
A floodwall can surround a home or it can protect isolated
openings, such as doors, windows, and walkout-on-grade base-
ments, depending on flood depths, site topography, and design
preferences. When built with decorative bricks or blocks or as
part of garden areas, floodwalls can become attractive architec-
tural or landscaping features. But they can also be built solely for
utility, usually at a lower cost.
Because a floodwall is made of concrete or masonry rather than
compacted earth, it is more resistant to erosion than a levee and
generally requires less space than a levee to provide the same
level of protection. But floodwalls are usually more expensive.
As a result, floodwalls are normally considered only for sites
where there is not enough room for a levee or where high-ve-
locity flows may erode a levee. Also, some homeowners prefer
floodwalls because they can be more aesthetically pleasing and
allow for the preservation of existing site features, such as trees.
As shown in Figure 3-17, an interior drainage system, including a sump pump, must be installed in the area pro-
tected by a levee or floodwall. The purpose of the system is to remove rainwater trapped inside the protected area
and, during flooding, to remove water that enters through seepage or infiltration.
Including an opening in a levee or floodwall may also be necessary to provide access for a car or other vehicle.
All openings must be equipped with closures similar to those used in dry floodproofing. Installing closures over
openings in levees and floodwalls requires advance warning of flooding in most cases—in other words, levees
and floodwalls generally require human intervention. One exception is a low, earthen levee that can be sloped to
allow vehicle access.
Table 3-10 presents the advantages and disadvantages of levees and floodwalls. Figure 3-19 shows a home pro-
tected by a floodwall.
DEFINITION
Riprap refers to pieces of rock or
crushed stone added to the surface of
a fill slope, such as the side of a levee,
to prevent erosion.
WARNING
Special design considerations are
necessary when levees or floodwalls
are built to protect a home with a
basement. Even though the surface
water is kept from coming into contact
with the home, the soil below the le-
vee or floodwall and around the home
can become saturated, especially
during floods of long duration. The re-
sulting pressure on basement walls
and floors can cause them to crack
buckle, or collapse.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-35
AN OVERVIEW OF THE RETROFITTING METHODS 3
Table 3-10. Advantages and Disadvantages of Levees and Floodwalls
Advantages Disadvantages
• Protects the area around the structure from inundation
without significant changes to the structure
• Eliminates pressure from floodwaters that would
cause structural damage to the home or other struc-
tures in the protected area
• Costs less to build than elevating or relocating the
structure
• Allows the structure to be occupied during
construction
• Reduces flood risk to the structure and its contents
• Reduces the physical, financial, and emotional strains
that accompany flood events
• Does not satisfy the NFIP requirements for bringing
Substantially Damaged or Improved structures into
compliance
• May fail or be overtopped by large floods or floods of
long duration
• May be expensive
• Requires periodic maintenance
• Requires interior drainage
• May affect local drainage, possibly resulting in water
problems for others
• Does not reduce flood insurance premiums
• May restrict access to structure
• Requires considerable land (levees only)
• Does not eliminate the need to evacuate during floods
• May require warning and human intervention for
closures
• May violate applicable codes or regulations
• Individual residential levees or floodwalls cannot be
used to bring a home with a first floor elevation below
the BFE into compliance with the NFIP
• May not be ideal for homes with basements because
hydrostatic pressure on below-ground portions of the
home can lead to structural failures
• May require a professional determination that the BFE
did not increase in the project area, which could make
levees and floodwalls difficult and expensive to design
NFIP = National Flood Insurance Program
NOTE
The costs for levee construction can
vary greatly, depending on the dis-
tance between the construction site
and the source of the fill dirt used to
build the levee. The greater the dis-
tance that fill dirt must be hauled, the
greater the cost.
3-36 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
3 AN OVERVIEW OF THE RETROFITTING METHODS
Figure 3 19. A home
protected by a floodwall
designed as a landscaping
feature.
Table 3-11 shows the relative costs for levees and floodwalls of various heights. Additional costs for erosion pro-
tection using seeding or riprap, interior drainage, and installation of closures may be required for levees and
floodwalls. Figure 3-20 illustrates the dimensions of these structures.
Table 3-11. Relative Costs of Levees and Floodwalls
Construction Type Existing Foundation Retrofit Relative Cost
Frame, Masonry Veneer, or
Masonry
Basement, Crawlspace,
Open Foundation, or
Slab-on-Grade
Levee constructed 2 feet above grade Lowest
Highest
Levee constructed 4 feet above grade
Floodwall constructed 2 feet above grade
Levee constructed 6 feet above grade
Floodwall constructed 4 feet above grade
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-37
AN OVERVIEW OF THE RETROFITTING METHODS 3
Figure 3-20. Example of floodwall and levee dimensions.
3.5 Summary
To protect your home from flooding, you may be able to use one or more of the retrofitting methods described in
this chapter. However, some retrofitting methods are probably inappropriate for your home and some may not be
allowed by your State or community. Also, if the Substantial Improvement and Substantial Damage requirements
do not apply to your home, you may be faced with decisions about the level of protection you are willing to pay
for and the level of risk you are willing to accept. Table 3-12 provides a comparison of the relative costs of each of
the retrofitting methods listed in this chapter based on home construction type and foundation type.
Chapter 4 will help you decide on a method. Note that cost is not the only consideration when evaluating miti-
gation measures. Depending on your decision, you can move on to Chapter 5, 6, or 7 for a detailed look at your
preferred method.
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3 AN OVERVIEW OF THE RETROFITTING METHODS
Table 3-12. Relative Costs of Various Retrofit Measures
Construction Type Existing Foundation Measure Retrofit Relative Cost
Frame, Masonry
Veneer, or Masonry
Crawlspace or
Basement
Wet
Floodproofing Wet floodproof crawlspace to a
height of 4 feet above lowest
adjacent grade or wet floodproof
unfinished basement to a height
of 8 feet above basement floor
Lowest
Highest
Masonry Veneer or
Masonry
Slab-on-Grade or
Crawlspace
Dry Floodproofing
Dry floodproof to a maximum
height of 3 feet above lowest
adjacent grade
Frame, Masonry
Veneer, or Masonry
Basement,
Crawlspace, or Open
Foundation
Barrier Systems
Levee constructed to 6 feet above
grade or floodwall constructed to
4 feet above grade
Frame, Masonry
Veneer, or Masonry
Basement,
Crawlspace, or Open
Foundation
Elevation
Elevate on continuous foundation
walls or open foundation
Frame, Masonry
Veneer, or Masonry
Basement,
Crawlspace, or Open
Foundation
Relocation
Elevate on continuous foundation
walls or open foundation
Frame, Masonry
Veneer, or Masonry Slab-on-Grade
Elevation
Elevate on continuous foundation
walls or open foundation
Frame, Masonry
Veneer, or Masonry Slab-on-Grade
Relocation
Elevate on continuous foundation
walls or open foundation
Frame, Masonry
Veneer, or Masonry
Slab-on-Grade,
Crawlspace, Base-
ment, or Open
Foundation
Demolition
Demolish existing building and
buy or build a home elsewhere Varies
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-1
4.0 Deciding Which Method is
Right for Your Home
With the information from Chapters 2 and 3, you are ready to decide which retrofitting method is right for your
home. Your decision will be based primarily on hazards to your home, permit requirements, the technical limi-
tations of the methods, and cost. Other considerations might include such things as the appearance of the home
after retrofitting and any inconvenience resulting from retrofitting. Making a decision involves four steps:
The four steps are described in the next section. In Appendix G, you will find a retrofitting checklist that will
help you work with local officials, design professionals, and retrofitting contractors. The checklist includes spaces
where you can record the results of Steps 1 and 2, important questions you should ask, and decision-making ma-
trices that will help you choose a retrofitting method. Before you go any further, you may want to make a copy of
the checklist (see Appendix G) so that you can begin filling it out.
4-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
4.1 Making Your Decision
4.1.1 Step 1 – Determine the Hazards to Your Home
If you are using this guide, your home has probably been dam-
aged by flooding or you know that it is in a flood hazard area.
Refer to Section 2.3 for descriptions of each of the hazards in
the checklist. Information about flooding and other hazards in
your area is available from local officials, as discussed later in
Step 3. But if your home has been flooded, review what you al-
ready know. Look at the Step 1 section of the checklist. Answer
as many of the questions as you can. Local officials, design pro-
fessionals, and contractors can use the information you provide,
along with the flood hazard information developed by FEMA
and other agencies and organizations, to advise you about your
retrofitting options.
You also need to be aware of other hazards, such as high winds
(Figure 4-1), earthquakes (Figure 4-2), fires, landslides, and
tsunamis. If your home is in an area subject to one or more
of these hazards, your retrofitting project should take the ad-
ditional hazards into account. The foundation may need to be
reinforced and the connections between the foundation, walls,
and roof may need to be strengthened as part of the retrofit-
ting project. Depending on the nature of the hazards and your
choice of retrofitting methods, State and local regulations may
require that additional changes be made to your home, beyond
those necessary for flood protection. Your local officials can tell
you if such requirements apply and can give you more informa-
tion. General information for different hazards can be obtained
as follows:
n Wildland fire: Wildland fire risk information is available
from the U.S. Forest Service at http://www.fs.fed.us/
fire/
n Tsunami: Tsunami hazard maps are available from the
NOAA Center for Tsunami Research at http://nctr.pmel.
noaa.gov/time/resources/
NOTE
The results of Steps 1 and 2 will help
your local official to advise you and
will also be useful when you consult
a design professional or retrofitting
contractor.
DEFINITION
A tsunami is a large, rapidly moving
sea wave or series of waves produced
by an undersea earth movement
(earthquakes, crustal displacements,
or landslides) or volcanic eruption.
NOTE
The retrofitting checklist provided in
Appendix G references Figure 4-1
and Figure 4-2. If you are unable to in-
terpret these maps, local officials and
design professionals will be able to
help you. Exposure to hazards quanti-
fied in Figure 4-1 and Figure 4-2 may
limit the options available to safely
retrofit your home.
WARNING
If you are retrofitting a home that is being Substantially Improved or has been Substantially Damaged,
your community’s floodplain management ordinance, regulation, or provisions of the building code will
not allow you to have a basement, as defined by the NFIP, below the BFE. The NFIP regulations define
a basement as “any area of the building having its floor subgrade on all sides.” If your home has such a
basement, you will be required to fill it in as part of any elevation project. See Section 2.3.1 for the NFIP
definition of a basement.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-3
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
n Landslide: Landslide risk information is available from the U.S. Geologic Survey at http://landslides.usgs.
gov/
4.1.2 Step 2 – Inspect Your Home
The discussion in Chapter 3 may have prompted you to begin thinking about your home, specifically how it is
constructed and the type of foundation it has. Before you check with your local officials or consult a design pro-
fessional and contractor, you should inspect your home and fill out the section of the checklist for Step 2. Four
characteristics of your home that are particularly important in retrofitting are construction type, foundation type,
lowest floor elevation, and condition. (When you fill out the portion of the checklist concerning construction and
foundation type, you may want to refer to the descriptions in Chapter 3.)
Construction Type
As explained in Chapter 3, the construction type for most homes will be frame, masonry veneer, masonry, modu-
lar, manufactured, or a combination of two or more of these types. The following generalizations can be made
about the effect of construction type on retrofitting:
n The most appropriate elevation technique for frame homes and manufactured homes usually is to elevate
on extended foundation walls or open foundations.
n Masonry homes are frequently elevated by extending the walls of the home upward and raising the
lowest floor or by abandoning the lowest floor and moving the living area to an existing or new upper
floor.
n Frame homes, masonry veneer homes, and manufactured homes are easier to relocate than masonry
homes.
n Masonry and masonry veneer homes are usually easier to dry floodproof than other types of homes,
because masonry is a more flood damage-resistant material than the materials used in frame homes.
Foundation Type
As explained in Chapter 3, most homes of the construction types listed above are built on a basement, crawlspace,
slab-on-grade, or open foundation or on a combination of two or more of these types. The following generaliza-
tions can be made about the effect of foundation type on retrofitting:
n Homes on basement or crawlspace foundations are easier to elevate than slab-on-grade homes.
n Elevating homes on basement foundations normally involves elevating or relocating utility system
components typically found in basements, such as furnaces and hot water heaters.
n Homes on basement foundations should not be dry floodproofed or protected by levees or floodwalls
unless an engineering evaluation conducted by a design professional shows that it is safe to do so. This
precaution is necessary because neither dry floodproofing nor the construction of levees or floodwalls
prevents saturated soils from pressing on basement walls. This pressure, which is unequalized because
water is not allowed to enter the basement, can damage basement walls or even cause them to fail.
n For some homes on basement foundations, an engineering evaluation is a necessary part of a wet
floodproofing project. If the home is in an area where saturated soils begin to press on basement walls
before water enters the basement, the unequalized pressure may damage walls or cause them to fail. If
wet floodproofing is to be used in this situation, the engineering evaluation must show that the basement
walls can resist the expected pressure.
4-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
Figure 4-1. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings and Other Structures,
ASCE/SEI 7-10. Used with permission from ASCE.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-5
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
Figure 4-1 continued. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings and Other
Structures, ASCE/SEI 7-10. Used with permission from ASCE.
4-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
Figure 4-2. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II structures
located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration with the
Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource Support
Committee (CRSC).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-7
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
Figure 4-2 continued. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II
structures located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration
with the Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource
Support Committee (CRSC).
4-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
Figure 4-2 continued. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II
structures located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration
with the Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource
Support Committee (CRSC).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-9
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
Lowest Floor Elevation
As noted in Chapter 3, the “lowest floor” of your home, as defined by your community’s floodplain management
ordinance, regulation, or provisions of the building code, is not necessarily the first or finished floor. For example,
the lowest floor could be the floor of a basement or the floor of an attached garage. As shown in Figure 4-3, the
location of your lowest floor can vary with foundation type. For homes that are to be elevated, wet floodproofed,
or dry floodproofed, the difference between the elevation of the lowest floor and the DFE determines how high
the home must be elevated or how high the wet or dry floodproofing protection must reach. In general, as the
difference between the lowest floor elevation and the DFE increases, so does the cost of elevating, wet floodproof-
ing, or dry floodproofing. This difference is particularly significant for dry floodproofing. As noted in Chapter 3,
even masonry walls should not be dry floodproofed higher than 3 feet unless a structural evaluation by a design
professional shows that it is safe to do so.
The elevation of your lowest floor can be established by a survey, which may be necessary as part of your retro-
fitting project. But even if you do not know your lowest floor elevation, you can estimate the difference between
it and the flood protection elevation. Your conversations with your local officials, design professionals, and con-
tractors will help you determine the level of flood protection you should provide. Remember, if your home is being
Substantially Improved or has been Substantially Damaged according to your community’s floodplain management ordinance, regulation, or provi-
sions of the building code, your flood protection elevation must be at least equal to the DFE. As explained in Step 3, your local officials
can tell you about this requirement.
Elevation certificates are used to determine insurance premium
rates under the NFIP. If your community participates in the NFIP,
it must obtain the as-built elevation of the lowest floor for all
new or Substantially Improved structures in SFHAs. Your com-
munity may use FEMA’s elevation certificates to keep track of
lowest floor elevations for all of the new and Substantially Im-
proved structures in flood zones. Communities that participate
in the NFIP CRS are required to obtain and maintain elevation
certificates.
If an elevation certificate already exists for your home, it will
provide information about your specific property, including:
n Property information, including address, building use,
and foundation information
n FIRM information, including panel number and BFE
n Building elevation information determined by a survey
n Certification by an engineer, architect, or surveyor
n Photographs of the building
Elevation certificates must be completed by a land surveyor, engineer, or architect who is licensed in your State to perform
surveys. Instructions on completing the elevation certificate and the form itself may be found on the FEMA Web site at
http://www.fema.gov/media-library/assets/documents/160.
NOTE
Occasionally, a small area is inadver-
tently shown to be within the SFHA on
a FIRM, even though the ground is at
or above the BFE. If this occurs, an
individual property owner may sub-
mit survey information to FEMA and
request that FEMA issue a document
that officially removes a property from
the SFHA, called a Letter of Map
Amendment (LOMA).
4-10 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
Figure 4-3. Difference be-
tween flood level and lowest
floor in homes on crawlspace
and basement foundations.
Condition
Your design professional or contractor should conduct a detailed inspection of your home before beginning
any retrofitting work. You can help by first conducting your own assessment of the condition of your home and
recording any information you have about past or current damage. This information may also be helpful to com-
munity officials who advise you about floodplain management and building code requirements and appropriate
retrofitting methods.
If your home has been damaged by a flood, hurricane or other high-wind event, earthquake, fire, or other di-
saster, make a note of the extent of the damage, when it occurred, and whether it was repaired (the checklist
provided in Appendix G can be used to list these damages). If repairs were made, make a note of who made them
and describe what was done. Any structural damage and repairs
to walls, floors, foundations, and roofs is particularly impor-
tant. You should also describe any damage resulting from other
causes, such as foundation settlement, dry rot, and termite dam-
age. Your goal is to give your design professional and contractor
as much information as possible so that they can determine how
the condition of your home will affect your choice of a retrofit-
ting method.
Other Considerations
In addition to construction type, foundation type, lowest floor
elevation, and condition, you should make note of interior and
exterior service equipment that must be protected as part of
NOTE
A historic property is a resource
(i.e., building, structure, site, object,
or district) that is listed in or eligible
for listing in the National Register of
Historic Places or listed in a State or
local inventory of historic places. For
more information, visit your State’s
SHPO Web site (see Appendix E).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-11
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
your retrofitting project. Interior service equipment must be
protected if you elevate or wet floodproof your home. This
equipment includes furnaces, heating and air conditioning
ductwork, hot water heaters, large appliances, and electrical sys-
tem components, such as service panels, outlets, and switches.
Exterior service equipment must be protected if you elevate, wet
floodproof, or dry floodproof and, in some situations, if you
build a levee or floodwall. This equipment includes air condi-
tioning and heat pump compressors and electric and gas meters.
In a home that is dry floodproofed, all openings below the DFE should be sealed. These openings may include
doors and windows as well as openings for water pipes, gas and electric lines, dryer vents, and sump pump dis-
charge pipes. In a home that is wet floodproofed, dry floodproofed, or protected by a levee or floodwall, backflow
valves must be installed on all water and sewer lines with openings below the DFE. These valves prevent floodwa-
ters and wastewaters from backing up into your home. Chapter 9 describes how to protect interior and exterior
service equipment.
4.1.3 Step 3 – Check with Your Local Officials
This is a particularly important step. While you can obtain in-
formation from your FIS and your FIRM online (Chapter 2
discusses how to obtain FIRMs online), your local officials can
help you to interpret that information. They will have hard
copies of the FIS and FIRM published for your community by
FEMA. Your officials will be able to tell you whether your home
is in your community’s regulatory floodplain and, if so, the BFE
at the location of your home. They may also have information
about flood conditions near your home, including flow velocity,
the potential for wave action and debris flow, rates of rise and
fall, warning time, and duration of inundation.
Local officials will inform you of Federal, State, and local reg-
ulations, codes, and other requirements that can determine
what retrofitting methods you will be allowed to use and how
changes can be made to your home. They can also tell you about
Federal, State, and local programs that provide financial assis-
tance for homeowner retrofitting projects, and they can help
you determine whether you are eligible for such assistance.
With the information you recorded in Steps 1 and 2, local offi-
cials may also be able to advise you about the most appropriate
retrofitting method for your home. The officials you need to talk
to will depend on how your community has assigned responsi-
bilities for floodplain management and construction permitting.
If you do not know who has these responsibilities in your com-
munity, you should begin with an official such as a city clerk,
mayor, or county administrator.
Remember that if your property is individually historic, potentially historic, or within the boundaries of a his-
toric district and you are receiving Federal financial assistance for your retrofitting project, the Federal agency
NOTE
Elevation of electric and gas meters
is typically controlled by the utility
company.
NOTE
Be sure to ask local officials about
State or local freeboard requirements
that may apply to your retrofitting
project.
NOTE
In addition to meeting the minimum
requirements laid out in your local
floodplain ordinance, any retrofit ac-
tivities should comply with the current
building code. Talk to your design pro-
fessional about applicable codes and
standards.
4-12 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
providing the assistance must first satisfy Federal historic preservation compliance requirements. Your local offi-
cials may not be aware of these requirements if they do not normally deal with federally assisted projects. Should
historic preservation compliance be triggered, the Federal agency will need to consult with your SHPO. Remem-
ber that any compliance review must be completed before retrofitting work is initiated or the Federal assistance
could be jeopardized.
When you talk to your local officials, be sure to do the following:
n Bring this guide with you.
n Bring your completed retrofitting checklist.
n Discuss what you already know about your home and the hazards that affect it.
n Work through the points listed in the section of the checklist for Step 3.
n Ask any other questions you may have.
n Work through the decision-making matrix provided in Section 4.2 with the official. Use the matrix
that applies to your situation: Substantial Improvement / Substantial Damage or NOT Substantial
Improvement / NOT Substantial Damage.
n Take notes about everything you discuss.
Remember that your goal is to find out what you can legally do to retrofit your home, identify the requirements
you must comply with throughout the retrofitting process, and eliminate retrofitting methods that cannot be ap-
plied to your home or do not meet your needs. You may find that the restrictions and requirements of Federal,
State, and local regulations will eliminate some retrofitting methods from consideration. Ultimately, your decision
will be based on technical limitations of the methods, cost, and other considerations, such as the effect that ret-
rofitting will have on the appearance of your home. The decision-making matrices will help guide you through
this process.
Your next step, whether you have chosen one method or are considering two or more, is to consult a properly
licensed, bonded, and insured design professional and retrofitting contractor.
4.1.4 Step 4 – Consult a Design Professional and Retrofitting Contractor
To complete this step, you will need to know what types of services are required for your retrofitting project and
how to evaluate and select design professionals and contractors.
You will probably need the services of a contractor regardless of the retrofitting method you select. The type of
contractor you hire will depend on the method. You will likely also need to consult a design professional, such as
an architect or a structural engineer. Alternatively, you can hire a general contractor who will arrange for all the
necessary services, including those of a design professional. Table 4-1 shows the types of design professionals and
contractors that may be required for each of the retrofitting methods.
Knowing the types of services required for your retrofitting project is important, but so is hiring a reputable and
competent design professional and contractor.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-13
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
Table 4-1. Requirements for Design Professional and Contractor Services
Method Need for Design Professional
and/or Contractor Primary Services
Elevation Design Professional Evaluating the condition, stability, and strength of the existing
foundation to determine whether it can support the increased
load of the elevated home, including any wind and seismic loads,
or designing a new foundation
Contractor:
Home Elevation Contractor
Disconnecting utilities, jacking the home up, increasing the height
of the foundation or building a new foundation, and connecting
utilities
Wet
Floodproofing
Design Professional Designing any necessary replacements of vulnerable structural
materials and relocated utility systems
Contractor:
General Construction Contractor
Replacing vulnerable structural and finish materials below the
DFE with flood damage-resistant materials, raising utilities and
appliances to a location above the DFE, and installing openings
required to allow the entry of floodwaters
Relocation Design Professional Designing any new building, foundation, and site improvements
that may be required, such as new utility systems
Contractor:
Home Moving Contractor
Jacking the home up, moving it to the new site, and installing it
on the new foundation
Contractor:
General Construction Contractor
Preparing the new site (including grading, foundation con-
struction, and utilities) and restoration of the old site (including
demolition)
Dry
Floodproofing
Design Professional For masonry walls to be dry floodproofed, evaluating the condi-
tion, stability, and strength of the existing walls to verify whether
they can withstand the pressure from floodwaters at the DFE;
designing or selecting flood shields for doors or other openings
Contractor:
General Construction Contractor
Applying waterproof sealants and membranes, installing flood
shields over openings below the DFE, installing backflow valves
in sewer and water lines, and, if necessary, bracing or modifying
walls so that they can withstand the pressure from floodwaters at
the DFE
Levees and
Floodwalls
Design Professional Assessing the adequacy of soils at the site, preparing the engi-
neering design to ensure that the levee or floodwall, including any
closures required, will be structurally stable under the expected
flood loads and will be able to resist erosion, scour, and seepage
Contractor:
General Construction Contractor
Constructing the levee or floodwall
Mitigation
Reconstruction
Design Professional Designing any new building, foundation, and site improvements
that may be required, such as new utility systems
Contractor:
Demolition Contractor
Disconnecting and capping utility lines, tearing down the
damaged home, hauling away debris, and restoration of the site
Contractor:
General Construction Contractor
Building the new home on the restored site or new site; this
contractor may also be able to do all demolition work
DFE = design flood elevation
4-14 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
If you have used a licensed design professional and a licensed
contractor in the past and were satisfied with the work, you
might consider using them again. Even if they do not pro-
vide the types of services you now need, they may be able to
recommend someone who can. Otherwise, you can search on-
line or contact the professional association that represents the
types of specialists you are looking for. Appendix F contains a
list of the addresses and telephone numbers of several of these
associations. They can usually give you a list of members in
your area who specialize in the type of work you need. Before
you hire a design professional or a contractor, check with your
local Better Business Bureau, consumer protection agency, or
licensing authorities. These organizations can tell you whether
there have been any complaints about the quality of the design
professional’s or contractor’s past work, including whether the
work was completed on time.
Next, you will need to meet with the design professional and
contractor to discuss your project. At the meeting, be sure you
do the following:
n Provide the information you collected in Steps 1, 2,
and 3.
n Ask the questions listed on the retrofitting checklist
located in Appendix G, as well as any others you may
have.
n Verify that the design professional is licensed and
registered in the State in which the work will be done.
n Verify that the contractor is licensed, bonded, and
insured as required by State and local laws.
n Ask for proof of insurance. If the design professional
or contractor does not have disability and worker’s
compensation insurance, you may be liable for
accidents that occur on your property.
n Ask for references. Reputable design professionals and
contractors should be willing to give you the names of previous customers. Call some of them and ask
how satisfied they were with the work. Ask if they would hire the design professional or contractor again.
n If you are trying to decide between two or more retrofitting methods, discuss your preferences and ask
for more information.
Any design professional or contractor you hire will need to conduct a site visit to inspect your home and deter-
mine how the work should be carried out. During the site visit, you should expect your design professional or
contractor to assess the structural condition of your home and determine what changes will be required by the
retrofitting method you choose. If you agree on a method and decide to proceed with the project, be sure to do
the following:
WARNING
Areas recovering from floods are
often prime targets for less-than-
honest business activities. Here are
some pointers that can help you avoid
problems:
Check with your local Better Business
Bureau, consumer protection agency,
or licensing authorities before you hire
a contractor.
Beware of “special deals” offered
after a disaster by contractors you
don’t know.
Beware of unknown contractors who
offer to use your home as a “model
home” for their work.
Do not sign any contract under pres-
sure by a salesperson. Federal law
requires a 3-day cooling-off period for
unsolicited door-to-door sales of more
than $25.
Beware if you are asked to pay cash
on the spot instead of with a check
made out to the name of a business.
Ask contractors for references. A
reputable contractor should be able to
give you a list of past clients in your
area who can comment on the quality
of the contractor’s work.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-15
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
n Get a written, signed, and dated estimate. It should cover everything you expect to be done. (Some
design professionals and contractors will charge a fee to prepare the estimate.)
n Get signed and stamped building plans that show details of the proposed retrofitting measure.
n Decide whether you, the design professional or contractor will obtain the necessary permits.
n Ask for a warranty or guarantee. Any warranty or guarantee from the design professional or contractor
should be written into the contract. The contract should clearly state the terms of the warranty or
guarantee, who is responsible for honoring it (such as a manufacturer or the contractor), and how long
it will remain valid.
n Get a written contract. It should be complete and clearly state all work to be done, the estimated cost, the
payment schedule, and the expected start and completion dates for the work.
Note that, if a project is funded by a FEMA HMA grant, starting construction prior to FEMA’s approval or award
of the grant can jeopardize grant funding.
4.2 Decision-Making Matrices
This section provides two matrices that can help you decide which retrofitting method will best meet your needs.
If your home is either being Substantially Improved or has been Substantially Damaged, the NFIP regulations limit
your choice of retrofitting methods to elevation, relocation, or demolition (Table 4-2). If your home is NOT being
Substantially Improved or has NOT been Substantially Damaged, additional retrofitting methods may be consid-
ered, such as dry floodproofing, wet floodproofing, and construction of levees or floodwalls (Table 4-3).
You may require guidance while using the matrix. Local officials, design professionals, and contractors can help
you evaluate factors you are unsure about, so take the matrix with you when meeting with them. This will be help-
ful to determine which methods are cost prohibitive or are not technically feasible.
After you have identified the appropriate matrix to use, identify any methods eliminated by regulations, ordinances,
or laws established by State or other agencies and organizations. Also, you may have already decided that one or
more methods will not meet your needs. Mark each eliminated method by placing an “X” in the box directly be-
low the name of the method (on the line labeled “Prohibited by Federal, State, or Local Regulations or Eliminated
by Homeowner”). An “X” in this row means that the method is eliminated and will not be considered further.
The next step is to evaluate the remaining methods. Your evaluation will be based on the factors listed on the left
hand side of the matrix. The factors are explained below. For each evaluation factor under each method, discuss
your concerns with your local official, design professional, and contractor. If your concerns cannot be resolved,
place an “X” in the appropriate box. After you have worked through the entire matrix, add the number of “Xs”
under each method and show the sum on the Total “Xs” line. Remember, each “X” is based on your preferences
and the input of local officials, design professionals, and contractors. So, although not all factors are equally criti-
cal, the method with the lowest total “Xs” will probably best meet your needs.
4.2.1 Evaluation Factors
Federal, State, and Local Restrictions – Federal, State, and local regulations may restrict the homeowner’s choice
of retrofitting measures. Such regulations may include State and local building codes, floodplain management
ordinance, regulation, or provisions of the building code, zoning ordinances, Federal regulations concerning
the alteration of buildings classified as historic structures, deed restrictions, and the covenants of homeowners’
4-16 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
associations. The homeowner and the homeowner’s design professional or contractor should check with commu-
nity officials to determine whether any such restrictions apply.
Appearance – The final appearance of a home and property after retrofitting will depend largely on the retrofit-
ting method used and the DFE. For example, elevating a home several feet will change its appearance much more
than elevating only 1 or 2 feet, and wet floodproofing will change its appearance very little. However, a change in
appearance will not necessarily be a change for the worse (see photographs in Chapter 3). The homeowner should
discuss the potential effects of each method with local officials and with the design professional or contractor.
Cost – The cost of retrofitting will depend largely on the retrofitting method used and the flood protection eleva-
tion. For some methods, the construction type (frame, masonry, etc.) and foundation type (crawlspace, slab, etc.)
will also affect the cost. In general, costs will increase as the flood protection elevation increases, but there may
be tradeoffs between alternative methods. For example, elevating may be less expensive than relocating when a
home is raised only 1 or 2 feet, but may become more expensive at greater heights. Other costs include those for
both routine and long-term maintenance and insurance premiums. Adding additional freeboard to an elevation
project will generally increase the project’s cost; however, the additional freeboard may produce significant savings
on insurance premiums. The annual savings on insurance premiums may quickly return the investment required
to add freeboard.
Accessibility – Accessibility refers to how easy or difficult it is to routinely reach and enter the home after the
retrofitting project is completed. The retrofitting methods described in this guide affect accessibility in different
ways. For example, elevating a home will usually require the addition of stairs, which may be unacceptable to
some homeowners. In these cases, homeowners may have to consider installing small elevators or using an entire-
ly different retrofit method. Levees and floodwalls can make access more difficult unless they are equipped with
openings, which require human intervention (see below). Wet floodproofing will have little if any effect on acces-
sibility. Dry floodproofing openings can be very expensive; often points of access are sealed off to control project
costs. The effect of relocation on accessibility will depend on the location and configuration of the new site.
Code-Required Upgrades – State and local regulations may require that a retrofitted home be upgraded to meet
current code requirements that were not in effect when the home was built. Portions of the electrical, plumbing,
and HVAC systems could be affected. For example, the electrical panel might have to be upgraded from fuses to
circuit breakers. These changes are required for the safety of the homeowner. Other code-required upgrades in-
clude those for increased energy efficiency. Any required upgrade can add to the scope and cost of the retrofitting
project. The homeowner and the homeowner’s design professional or contractor should check with community
officials to determine whether such regulations apply.
Human Intervention – For retrofitting methods that require human intervention, homeowners must be willing,
able, and prepared to take the necessary action, such as operating a closure mechanism in a floodwall or plac-
ing flood barriers across the doors of a dry floodproofed home. Also, the homeowner must always have adequate
warning of a coming flood and must be at home or near enough to be able to reach the home and take the neces-
sary action before floodwaters arrive. If these conditions cannot be met, retrofitting methods that require human
intervention should be eliminated from consideration.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-17
DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4
4.2.2 Substantial Improvement / Substantial Damage Matrix
Table 4-2. Retrofitting Methods for Substantially Improved or Substantially Damaged Homes
Retrofitting Methods
Substantially Improved or Substantially Damaged Homes
Evaluation
Factors
Elevation1
Relocation Demolition
Elevation on
Extended
Foundation Walls
Elevation
on Open
Foundation
New Living Area
over Abandoned
First Floor
Prohibited by
Federal, State, or
Local Regulations
or Eliminated by
Homeowner
Appearance
Cost
Accessibility
Code-Required
Upgrades
Human
Intervention
Other
Total “Xs”
1 Note that if you elevate a Substantially Improved or Substantially Damaged home, you can still wet floodproof an
enclosed area under the home below the BFE, provided that: (1) the area is only used for parking, building access, and
storage, (2) the area is designed to allow for automatic entry and exit of flood waters through the use of openings, and (3)
the area is constructed with flood damage-resistant materials.
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4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME
4.2.3 NOT Substantial Improvement / NOT Substantial Damage Matrix
Table 4-3. Retrofitting Methods for Homes That are NOT Substantially Improved or Damaged
Retrofitting Methods
for Homes NOT Substantially Improved or Substantially Damaged
Evaluation
Factors
Elevation
Relocation Dry
Floodproofing
Wet
Floodproofing
Levees or
Floodwalls Demolition
Elevation on
Extended
Foundation
Walls
Elevation
on Open
Foundation
New Living
Area over
Abandoned
First Floor
Prohibited by
Federal, State, or
Local Regulations
or Eliminated by
Homeowner
Appearance
Cost
Accessibility
Code-Required
Upgrades
Human
Intervention
Other
Total “Xs”
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-1
5.0 Elevating Your Home
One of the most common retrofitting methods for homes is elevation. When a home is properly
elevated, the living area should be above most flood levels. Several elevation techniques are avail-
able. In general, they involve lifting the home and building a new foundation or extending the
existing foundation below it, or leaving the home in place and either building a new elevated floor
system within the home or adding a new upper story and converting the ground level to a compliant
enclosure.
During the elevation process, most frame, masonry veneer, and masonry homes are separated from their founda-
tions, raised on hydraulic jacks, and held by temporary supports while a new or extended foundation is constructed
below. The living area is raised so that only the foundation remains exposed to flooding. This technique works well
for homes originally built on basement, crawlspace, and open foundations. When homes are lifted with this tech-
nique, the new or extended foundation can consist of continuous walls or separate piers, posts, columns, or piles.
Masonry homes are more difficult to lift, primarily because of their design, construction, and weight, but lifting
these homes is possible. In fact, numerous contractors throughout the United States regularly perform this work.
A variation of this technique is used for frame, masonry
veneer, and masonry homes built on slab-on-grade foundations.
In these homes, the slab forms both the floor of the home and
either all or a major part of the foundation. Although elevating
these homes with the walls and slab attached and lifting them
together may appear easier, this may not be a viable option. A
slab-on-grade home should be inspected by a structural engi-
neer to determine whether the slab is sufficient to support the
house without being continuously supported by the soil it was
designed to sit on top of. If the slab isn’t strong enough to be
lifted, the walls can be elevated and a new wood floor system
constructed.
For masonry homes on slab-on-grade foundations, an alternative mitigation technique in which the home is left
on its original foundation may be easier. This technique involves removing the roof and raising the living space,
either by extending the walls of the home and raising the floor or by abandoning the lower level and moving the
living space to an existing or newly constructed upper floor. Another alternative for homes with high ceilings may
be to shift the floor system on the upper floors reducing the ceiling height, but creating space above the BFE to
construct a new first floor. The abandoned lower enclosed area is then converted to a compliant enclosure that is
used only for parking, building access, or storage. See Section 5.2.2 for more information.
NOTE
Always use a licensed, bonded, and
insured contractor for elevation proj-
ects. Be sure that your contractor has
experience with elevation projects
and understands the considerations
discussed in Section 5.1. Prior to
hiring a contractor, be sure to check
references.
5-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
5 ELEVATING YOUR HOME
In both of these techniques, portions of the original walls will be below the DFE. This approach is appropriate for
masonry construction, but not for frame construction, because of potential code compliance issues and flood in-
surance implications for wood-frame foundations.
This chapter describes and illustrates various elevation methods and discusses the most important considerations
regarding elevation. Remember, you should never attempt an elevation project without the help of experienced
design and construction professionals.
5.1 Considerations
Prior to elevating a home, a number of factors, such as how high to elevate, whether to incorporate the existing
foundation, other hazards (wind, earthquake, etc.), how access to the house will be accomplished, and which
elevation technique is appropriate, should all be considered. Some common factors to consider in elevating your
home are described in the sections that follow.
5.1.1 Amount of Elevation
The amount of elevation required is determined by the flood
protection elevation you have chosen. The minimum elevation
should be determined based on various sources of information.
Decisions need to be made based on the effective date of the
FIRM and whether any additional data, such as changes to the
flood source around the building site or flooding events since
the FIRM, may make is necessary to elevate higher. Homeowners
should also consider that potential future changes to the factors
that influence floods may result in higher flood events. Resourc-
es such as Hurricane Sandy Recovery Advisory No. 5, Designing
for Flood Levels Above the BFE After Hurricane Sandy (FEMA.2013b), may
provide some helpful guidance on how to determine your flood
protection elevation. Consider whether the locally enforced
elevation requirements are sufficient or whether you should
consider elevating even higher. For example, if your house is located in Zone A, you may only be required to
elevate your home to the BFE so that the top of the lowest floor is at or above that elevation (see Figure 5-1).
However, elevating 1 or 2 feet higher will provide increased protection and result in lower annual flood insurance
premiums.
As explained previously, if your home is being Substantially Improved or has been Substantially Damaged, your
community’s floodplain management ordinance, regulation, or provisions of the building code will require that
your lowest floor be elevated to or above the BFE. If Substantial Improvement and Substantial Damage requirements
do not apply, you may be able to elevate to any height you wish. Keep in mind that raising your home to an elevation
below the BFE not only provides less protection, but will not provide the lower insurance premiums that come with
elevation to or above the BFE. If you decide to raise your home to an elevation below the BFE, the community is re-
quired to evaluate the cost of all improvements, including the cost to elevate your home to determine whether your
proposed project is a Substantial Improvement. Regardless of whether your home is being Substantially
Improved or has been Substantially Damaged, you should consider incorporating at least 1 foot of freeboard into
your flood protection elevation (as shown in Figure 5-1). Often this will ensure that at a minimum, the floor
framing will be elevated above the floodwaters.
NOTE
FEMA HMA grants will only support
elevation projects to the flood pro-
tection elevation stipulated by the
engineering standard ASCE 24, Flood
Resistant Design and Construction,
or higher. In most instances, the mini-
mum elevation will be the BFE plus at
least 1 foot of freeboard.
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ELEVATING YOUR HOME 5
Elevating a home to 3 or 4 feet above the existing ground level usually will not have a great effect on its appear-
ance and will require only minimal landscaping and regrading. If you plan to elevate more than 4 feet above the
existing grade, you should consider elevating your home a full story. Not only will your home be protected against
deeper floods, but you can use the space below for parking, building access, or storage (Figure 5-2). If you decide
to incorporate parking under a living area, verify that any necessary code requirements have been addressed in
the retrofit. This could include providing a fire-rated floor assembly between the parking area and the living area
above. Hurricane Isaac Recovery Advisory 1, Minimizing Wind and Water Intrusion by Covering the Underside of Elevated Buildings
(FEMA. 2012c), provides some guidance on such assemblies.
Figure 5-1. As shown in the
cutaway view, the lowest
floor is above the flood
level. When at least 1 foot of
freeboard is provided, only
the foundation is exposed to
flooding.
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WARNING
If your home is being Substantially Improved or has been Substantially Damaged and is in a Coastal
High Hazard Area (Zone V, VE, or V1–V30 on the FIRM for your community), your community’s flood-
plain management ordinance, regulation, or provisions of the building code requires that the bottom of
the lowest horizontal structural member (rather than the lowest floor) be elevated to or above the BFE. In
many homes, the lowest horizontal structural member is a beam that supports the framing of the lowest
floor. With the exception of Elevating on an Open Foundation (Section 5.2.3), the elevation techniques
presented in this guide are not appropriate for homes in Coastal High Hazard Areas. If you have any
doubt about the type of flood hazards that may affect your home, check with your local officials.
Figure 5-2. This home in
Cedar Falls, IA, was elevated
one full story. The garage
and storage area are at the
home’s original elevation.
5.1.2 Existing Foundation
In general, the most economical approach to elevating a
home is to use as much of the existing foundation as possible.
Although some elevation methods do not allow this approach,
most do. If you choose one of the latter, a design professional
must evaluate the capacity of your existing foundation to sup-
port the loads that will be imposed by the elevated home and,
as discussed in the next section, the loads expected to result
from flooding and other hazards at the site. If changes must
be made to the foundation to increase its strength and stability,
they can be made as part of your retrofitting project. A design
professional may determine that an older foundation con-
structed of mortared rock, masonry, or even poured concrete
needs to be completely replaced or the local building code may
require that it be replaced.
CROSS REFERENCE
Fill used for structural support and el-
evation is prohibited in Coastal High
Hazard Areas. Check with your lo-
cal officials about State and local
requirements considering the use of
fill. NFIP Technical Bulletin 5, Free-
of-Obstruction Requirements (2008),
offers further guidance about using fill
in Zone V.
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ELEVATING YOUR HOME 5
The type of foundation on which your home was originally built (basement, crawlspace, slab-on-grade, piers,
posts, piles) also can affect the elevation process. This issue is discussed in Section 5.2.3.
5.1.3 Hazards
Because so many elevation techniques are available, elevation is practical for most flood situations, but the flooding
conditions and other hazards at the home site must be examined so that the most suitable technique can be deter-
mined. Regardless of the elevation technique used, the foundation of the elevated home must be able to withstand
all the necessary loads (wind, seismic, snow, etc.) on the house, which also should include the expected flood
loads from buoyancy, hydrostatic pressure, hydrodynamic pressure, and debris impact. It must also be able to resist
undermining by any expected erosion and scour.
If you are elevating a home in an area subject to high winds, earthquakes, or other hazards, a design profes-
sional should determine whether the elevated home, including its foundation, will be able to withstand all of the
horizontal and vertical forces expected to act on it. In making this determination, the design professional must
consider a number of factors, including the structure and condition of the home, the soil conditions at the site,
the proposed elevation technique, and the hazards at the site. The conclusion may be that additional modifications
must be made during the retrofitting project. In some flooding conditions, another alternative, such as relocation,
may be a better option. High wave loads, swift currents, or unstable soil may make relocation necessary. Some-
times the condition of the house and the necessary retrofits may also indicate that reconstruction of the entire
house is a more cost-effective option.
5.1.4 Access
Elevating a home usually requires that new means of access be provided. For example, if your entry doors were
originally at ground level, new staircases, elevators, or ramps will have to be built. When an attached garage is
elevated, providing access for vehicles may require changes to portions of your lot, such as building a new, el-
evated driveway that ties into high ground elsewhere. This solution can be practical when the amount of elevation
required is no more than 2 or 3 feet. As noted earlier, when the amount of elevation reaches 4 or more feet, you
should consider elevating your home a full story so that you can use the lower level for parking and avoid the
need for an elevated driveway. Constructing a means of access can be a considerable cost and should be included
in the price for the elevation.
Figure 5-3. With attention
to detail and planning,
homeowners have created
attractive retrofitted homes.
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5 ELEVATING YOUR HOME
The need to provide a new means of access is often the main objection that homeowners have to elevating. But
functional and attractive solutions to this problem can usually be developed, as shown in Figures 2-2 and 5-3.
5.1.5 Home Size, Design, and Shape
In general, the larger the home and the more complex its design and shape, the more difficult it will be to lift on
jacks. Multistory homes are more difficult to stabilize during the lifting process and, as the dimensions and weight
of a home increase, so do the required numbers of jacks and other pieces of lifting equipment. Exterior wall cover-
ings such as stucco and brick veneer complicate the lifting process because they must either be removed or braced
so that they will stay in place when the home is lifted. Homes with simple square or rectangular shapes are easier
to lift than those with attached garages, porches, wings, or additions, which often must be detached and lifted
separately, especially if they are built on separate foundations. Features such as chimneys can also add to the cost
of lifting a house because they must be either braced or removed during the lifting process. Older properties may
also include features such as cisterns, which may create access issues and result in higher lifting costs.
Before a home is lifted, a design professional should inspect it to verify its structural soundness. All the structural
members and their connections must be able to withstand the stresses imposed by the lifting process. Lifting an
unsound home can lead to potentially expensive damage.
5.1.6 Service Equipment
Before your home is elevated, all utility lines (water, sewer, gas,
electric, telephone, etc.) must be disconnected. At the end of
the project, the lines will be reconnected and any landscaping
that may be necessary will be completed. Adjustments may be
required for any overhead electrical service lines to ensure they
maintain all appropriate vertical and horizontal clearances. If
you elevate your home on an open foundation, utility lines that
enter the home from below may be exposed to damage from
flooding and below-freezing temperatures. Protecting utility
lines in these situations usually involves anchoring them secure-
ly to vertical foundation members and, if necessary, insulating them. All service equipment outside the home,
such as air conditioning and heat pump compressors, and gas and electric meters, must be elevated to or above the
flood protection elevation. In homes with basements, any service equipment originally installed in the basement
must be raised above the flood protection elevation, which may require relocation to an upper floor or a small
addition to house the equipment. Chapter 9 discusses the protection of service equipment. Moving or relocating
utility meters, such as natural gas or electric meters, may be at the discretion of the utility service provider. Pro-
viders may require meters to stay at elevations below the BFE.
5.2 The Elevation Techniques
The elevation techniques and their applications to different types of homes are discussed in the following sections.
5.2.1 Elevating on Extended Foundation Walls
Frame, masonry veneer, and masonry homes can all be elevated on extended foundation walls. As discussed in the
following sections, the technique used for homes on basements, crawlspaces, and open foundations differs from
that used for homes on slab-on-grade foundations. The potential for an elevated slab-on-grade foundation to fail
DEFINITION
Service equipment includes util-
ity systems, heating and cooling
systems, and large appliances in a
retrofitted home.
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ELEVATING YOUR HOME 5
either during the lifting process, or even worse once the house is occupied, makes this elevation technique one
that should be carefully scrutinized by a design professional familiar with the calculation of building loads and
the design of concrete slabs.
Homes on Basement Foundations and Crawlspace Foundations
The elevation process is the same for frame, masonry veneer, and masonry homes on basement and crawlspace
foundations. Figures 5-4a through 5-4d illustrate the process.
First, holes are made at intervals in the foundation wall so that a series of steel I-beams can be installed at criti-
cal points under the floor framing (Figure 5-4a). If the foundation walls are made of concrete blocks, the lifting
contractor can remove individual blocks to create the required holes. If the walls are made of poured concrete,
the holes will be cut out. The I-beams are placed so that they run perpendicular to the floor joists. A second set
of beams is then placed below and perpendicular to the first set (Figure 5-4a). The two sets of beams extend the
width and length of the home and form a cradle that supports the home as it is being raised.
In Figure 5-4a, the foundation walls are shown extending far
enough above the ground surface to provide easy access to the
area below the floor framing. However, in some homes, the
foundation walls will not be this high. To lift such a home, the
contractor must first dig trenches at intervals around the foun-
dation. The I-beams are then lowered into the trenches and
inserted below the floor framing. The contractor may also have
to dig holes for the lifting jacks, as shown in the figure. The
number of jacks needed will depend on the size, shape, and type
of home being lifted.
Once the beams and jacks are in place, the elevation process be-
gins. The jacks will extend only so high; so at intervals during
the process, the home and jacks are supported temporarily on
cribbing while the jacks are raised (Figure 5-4b). After the home is elevated high enough, it is again supported
on cribbing while the foundation walls are extended to the desired height with concrete blocks or poured con-
crete (Figure 5-4c). The home is then lowered onto the extended foundation walls, the I-beams are removed, and
the holes where the beams passed through are filled. An important part of the project is installing flood openings
in the foundation walls (your building permit should specify the size and location of these openings), no higher
than 1 foot above the ground, so that floodwaters can enter and equalize the internal and external hydrostatic
pressures. As shown in Figure 5-4c, the contractor may be able to create these openings by only partially filling
the I-beam holes.
CROSS REFERENCE
For more information about openings
requirements, refer to FEMA Technical
Bulletin 1, Openings in Foundation
Walls and Walls of Enclosures (2008),
and FEMA P-259, Engineering Prin-
ciples and Practices for Retrofitting
Flood-Prone Residential Structures
(FEMA. 2012a).
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Figure 5-4a through 5-4d.
Elevating a basement or
crawlspace foundation home
on extended foundation
walls.
5-4a
5-4b
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ELEVATING YOUR HOME 5
Figure 5-4a through 5-4d continued. Elevating a basement or crawlspace foundation home on extended foundation walls.
5-4c 5-4d
Homes on Slab-on-Grade Foundations
Frame, masonry veneer, and masonry homes on slab-on-grade foundations are also lifted with hydraulic jacks and
a network of steel I-beams. However, slab-on-grade homes present special difficulties and require a different lift-
ing technique. An alternative is to leave the existing slab and extend the walls (see Section 5.2.2), or convert the
ground level of the home and build a new upper floor (see Figures 5-12a through 5-12c). See Hurricane Sandy
Recovery Advisory No. 7, Reducing Flood Risk and Flood Insurance Premiums for Existing Residential Buildings in Zone A (FEMA.
2013e) for more information on doing such conversions.
The importance of evaluating the slab
To determine the best approach, the slab must be evaluated by a structural engineer. The engineer can determine
which elevation method is suitable for the house. Often the slab will not be of sufficient strength to span the dis-
tances necessary to use the standard interior pier spacings associated with wood-framed floor systems.
The floor of a home on a slab-on-grade foundation is formed by the slab rather than the wood joist and beam
framing found in homes on crawlspace and basement foundations. The slab is usually 3½ to 6 inches thick and is
often reinforced only with wire mesh. As shown in the cross-section view in Figure 5-5, the slab can be supported
by foundation walls and footings or by a thickened edge created when the slab is poured. Slabs are almost never
designed to be lifted and supported on a wall and pier system but rather to rest on the ground. If the slab is not
designed to be supported it could fail during elevation as a result of the loads. The wire mesh is often insufficient
to provide adequate reinforcing in the slab and is only intended to prevent the slab from cracking.
Because the slab forms the floor of the home, and occasionally the foundation as well, elevating a slab-on-grade
home is more difficult than elevating a house with a wood-framed floor system regardless of the lifting method
used. Because this process is more difficult than that used for homes on basement and crawlspace foundations, it
should be performed only by a highly skilled contractor with extensive experience in lifting slab-on-grade homes.
In lifting the slab, the contractor must take extreme care during the lifting process to avoid breaking the slab and
compromising the structural integrity of the home.
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5 ELEVATING YOUR HOME
Although the slab can be lifted while still attached to the walls, the slab may be dangerously weak once the house
is occupied. A more practical method may be to separate the walls from the slab and lift the house leaving the slab
in place. A new wood-framed floor can be constructed and the existing slab can remain in place.
Figure 5-5. Cross-section view of slab-on-grade foundation variations.
Elevating with the slab remaining in place
If a design professional determines that the original slab is strong enough to support the elevated home under the
expected flood, wind, earthquake, and other loads, the slab may be left in place and the new foundation walls built
on top of it. Otherwise, the slab must be cut back and a completely new foundation constructed, as shown in Fig-
ure 5-6. The lift is accomplished by cutting openings into the walls and inserting I-beams through the openings.
To enable the beams to lift the home, the contractor attaches horizontal wood bracing to the interior and exterior
walls at the tops of the openings (Figure 5-7). Figure 5-8 shows an example of a retrofitted slab-on-grade house
where the house was detached from the slab and a new floor system was constructed.
When the beams are jacked up, they push against the bracing, which distributes the lifting force equally across
the walls. The bracing also supports the walls, which lack the structural stability that would otherwise be pro-
vided when the walls and floor are left attached. Without bracing, the walls could twist, bend, or collapse when
the home is lifted.
Another option for elevations that do not exceed more than a few feet may be to construct a new elevated concrete
slab. Building a new slab floor involves placing fill dirt on top of the old slab and pouring a new slab on top of the
fill. Although the old slab is left in place, it is usually broken up so that it will not be forced up by the buoyant ef-
fect of floodwaters or saturated soil.
The primary advantage of lifting the home without the slab is that the home is lighter and, therefore, easier to lift.
This benefit applies mainly to frame and masonry veneer homes. However, this method has several disadvantages:
n Cutting holes in the interior and exterior walls of the home and attaching wood bracing is invasive and
must be repaired before the elevated home is habitable.
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ELEVATING YOUR HOME 5
n Because of the invasive lifting techniques, the habitable parts of the first floor may not be available for
use for an extended period of time during the project.
n The contents of the first floor must be removed before the elevation process can begin.
Figure 5-6. Building a new
foundation for a slab-on-
grade home.
Figure 5-7. Elevating a slab-
on-grade home without the
slab.
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Figure 5-8. House in Zone A
was detached from its slab
foundation (which remains)
and elevated on masonry
piers. The floor system is
supported by new wood
joists (Mandeville, LA).
Elevating with the slab attached
When the slab is determined to be of sufficient thickness and reinforced such that it can be supported on piers, the
slab can be lifted while still attached to the walls. The elevation process (Figures 5-9a through 5-9d) is similar to
that used for homes on basement and crawlspace foundations, except that the I-beams must be placed below the
slab, which is at ground level. Therefore, the contractor must dig trenches at intervals around the foundation, and
tunnel under the slab. The I-beams are lowered into the trenches and moved into place beneath the slab through
the tunnels (Figure 5-9a).
The contractor must also dig holes for the lifting jacks because they have to be placed below the beams. Once the
beams and jacks are in place, the lifting process begins. As shown in Figures 5-9b and 5-9c, the home is lifted and
a new foundation is constructed beneath it.
Some slab-on-grade houses are constructed on what are called stemwalls. These systems consist of a concrete foot-
ing with a short perimeter wall made of poured concrete or masonry block. If the slab was originally supported
by foundation walls and footings (see left and middle illustrations in Figure 5-5), the contractor may be able to
leave them in place and extend the existing walls upward. This approach is possible only when a design profes-
sional determines that the original foundation walls and footings are strong enough to support the elevated home
and slab under the expected flood, wind, earthquake, and other loads. If the slab was originally supported on the
ground by its own thickened edge (see right illustration in Figure 5-5), a completely new foundation must be
constructed.
In both situations, the contractor must construct not only foundation walls under the perimeter of the slab, but
also additional vertical foundation members, such as piers, at several locations under the slab. These additional
foundation members are necessary because slabs are designed to rest directly on the ground, not to support the
weight of the home.
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ELEVATING YOUR HOME 5
Figure 5-9a through 5-9d.
Elevating a slab-on-grade
home with the slab attached.
5-9a
5-9b
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Figure 5-9a through 5-9d
continued. Elevating a slab-
on-grade home with the slab
attached.
5-9c
5-9d
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ELEVATING YOUR HOME 5
The primary advantage of lifting the home with the slab still attached to the walls is that the home can remain
intact and many of the contents can remain inside during the lifting process. However, this method has several
disadvantages:
n Most slabs were constructed to be continuously supported by the ground underneath them and are
minimally reinforced. Insufficiently supporting such a slab can result in cracking or catastrophic failures
that could potentially injure the occupants.
n Retrofitting slabs with insufficient thickness or reinforcement can be expensive.
n If the house is not lifted evenly, the slab could crack during the elevation process.
n If uneven settlement occurs, the weight of the elevated slab may exceed the capacity of the masonry piers
commonly used for elevation projects.
Do not consider elevating a slab-on-grade house without seeking the help of a structural engineer. Although many
elevation contractors have experience elevating slab-on-grade houses, concrete has the potential to catastrophi-
cally fail and appropriately assessing the strength of the slab may be difficult for most contractors. Slabs cast on
the ground can have wide variations in thickness and the pier spacing may need to be adjusted once the bottom
of the slab becomes visible. Structural engineers familiar with the design requirements for slabs can properly ad-
dress the risk of a slab failure.
5.2.2 Alternative Elevation Techniques for Masonry Homes on Slab-on-Grade
Foundations
Elevating by Extending the Walls of the Home
An alternative technique for elevating a masonry home on a slab-on-grade foundation is to extend the existing
walls of the home upward and then build a new raised floor above the old slab. This technique is illustrated in
Figures 5-10a through 5-10c.
First the roof framing and roof are removed so that the tops of the walls will be accessible. The contractor can then
extend the walls upward with additional courses of either concrete block (as shown in Figure 5-10b) or brick or
with wood or metal framing. The choice of materials is based on several considerations, including cost, the final
appearance of the home, the strength of the existing foundation, and the design requirements associated with the
identified hazards, including high winds and earthquakes.
The final height of the extended walls will depend on how high the lowest floor must be elevated. For example,
if the lowest floor must be elevated 3 feet to reach the flood protection elevation, the height of the walls must be
increased by the same amount if the original ceiling heights in the home are to be maintained.
The new raised floor can be either a wood-framed floor system or an elevated concrete slab similar to the original
slab (referred to as a stemwall). When a new wood-framed floor system is installed, the area below the floor be-
comes a crawlspace (as in Figure 5-10c) or other enclosed area that may be used for parking, building access, or
storage. Flood openings must be installed in the foundation walls to allow external and internal water pressures
to equalize. Additional openings may be needed for ventilation.
For a new elevated slab floor, fill dirt is placed on top of the old slab and compacted as required. Then a new slab
is poured on top of the fill. When this method is used, openings in the foundation walls are not required because
the entire area under the new slab is completely filled with dirt and is therefore protected from the pressure of
floodwaters.
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5-10a
Figure 5-10a through 5-10c. Elevating by extending the walls
of a solid masonry home.
5-10b
5-10c
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ELEVATING YOUR HOME 5
Elevating by Abandoning the Lower Enclosed Area
Another alternative for a masonry home on a slab-on-grade
foundation is to abandon the existing lower enclosed area of the
home (the area with the slab floor) and allow it to remain be-
low the flood protection elevation. This technique requires that
the living area be restricted to upper floors of the home and
that the lower enclosed area be used only for parking, build-
ing access, or storage. Because this technique leaves the original
floor and walls below the flood protection elevation exposed to
flooding, it is best suited to masonry homes on slab-on-grade
foundations. In these homes, both the walls and floor are made
of concrete or masonry, which are not easily damaged by con-
tact with floodwaters. Only materials resistant to flood damage
should be used on portions of the building below the flood pro-
tection elevation.
The amount of work required for this technique depends largely on whether the home already has an upper floor
that can be used for living space. When an upper floor exists, abandoning the lower enclosed area involves remov-
ing any interior finishing materials below the flood protection elevation (including interior wall sheathing and
insulation unless required by code) and elevating or relocating vulnerable appliances (such as furnaces, washing
machines, and freezers) and utility system components (such as electrical wiring and service boxes). These modi-
fications are the same as those required for wet floodproofing, as described in Chapter 7.
This elevation measure may be the most practical for town houses or row houses. In an attached dwelling at least
one wall and usually two are common or “party” walls. These walls make lifting the actual walls impossible.
Shifting the elevation of the floor joists may be the only practical solution in these situations. This technique re-
quires significant alterations to the front and back walls of the unit or any walls that are not common to the other
units. These walls typically have the windows and exterior doors, which must be relocated (shifted up) as the
floor framing is shifted. Interior walls also must be removed and replaced with these projects. Although this is an
invasive method, the flood risk and potential financial implications of flood insurance premiums may make it a
palatable mitigation option. Figure 5-11 illustrates how this could be done for a row house with high ceilings.
This method also makes it possible to convert the ground floor to an NFIP-compliant enclosure and make adjust-
ments to the upper floors, such as moving utilities and mechanical equipment to higher floors. Uses appropriate
for areas below the BFE are described in Chapter 7.
For one-story homes, abandoning the lower enclosed area requires the construction of a new second story as
shown in Figures 5-12a through 5-12c. The required steps are similar to those described in Section 5.2.1. The roof
and roof framing are removed, a new second story is built on top of the existing walls, the roof and roof framing
are replaced, and openings are added for floodwaters. The construction options are the same: frame or masonry.
Again, the choice is based primarily on the considerations of cost, final appearance, the strength of the existing
foundation, and the need to address other natural hazards, such as high winds and earthquakes.
CROSS REFERENCE
For more information about flood open-
ings, refer to FEMA Technical Bulletin
1, Openings in Foundation Walls
and Walls of Enclosures (2008), and
FEMA P-259, Engineering Principles
and Practices for Retrofitting Flood-
Prone Residential Structures (FEMA.
2012a).
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Figure 5-11. Elevation of
the floor levels in a row
house to maximize living
area above the BFE in
Zone A (Source: Hurricane
Sandy Recovery Advisory 3
(FEMA. 2013f)).
Figure 5-12a through 5-12c.
Home elevated by adding a
new second story over an
abandoned lowest floor.
5-12a
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ELEVATING YOUR HOME 5
Figure 5-12a through 5-12c
continued. Home elevated by
adding a new second story
over an abandoned lowest
floor.
5-12b
5-12c
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Mitigation Reconstruction
Mitigation reconstruction is the construction of an improved, elevated building on the same site where an exist-
ing building and/or foundation has been demolished. There may be reasons why elevating your home may not be
feasible. If physical or economic obstacles are too great, you may want to consider demolishing your home and
rebuilding a code-compliant home that is elevated above the flood level (see Chapter 6).
For FEMA HMA grants, mitigation reconstruction is only permitted if traditional structure elevation cannot be
implemented. Activities that result in the construction of new living space at or above the BFE will only be con-
sidered when consistent with the mitigation reconstruction requirements.
5.2.3 Elevating on an Open Foundation
Frame, masonry veneer, and masonry homes on basement,
crawlspace, and slab-on-grade foundations can also be elevat-
ed on open foundations consisting of piers, posts, columns, or
piles. Homes originally constructed on open foundations can
also be elevated this way.
Piers
Figures 5-13a through 5-13d show how a home on a basement
or crawlspace foundation can be elevated on masonry piers. The
lifting process is the same as that shown in Figure 5-4 for elevat-
ing on extended foundation walls. Once the home is lifted high
enough, new masonry piers may be built on the existing foundation, if it is adequate. If the existing foundation
is not adequate to support the elevated home, it will have to be either modified or removed and replaced by sepa-
rate footings for the individual piers.
An existing basement must be filled in with dirt and graded. An old basement slab can be left in place and cov-
ered with fill dirt. A basement slab does not need to be removed, but it should be broken up in place so that it will
allow water to seep through it and reduce buoyancy forces before being covered with fill dirt. The home in Figure
5-13d has been elevated approximately one full story, and a new concrete slab has been poured at ground level
below it. The open area below the home can be used for parking, building access, or storage.
Piers can be constructed of cast-in-place concrete as well as fully grouted masonry blocks. However, regardless of
the construction materials used, piers are designed primarily for vertical loading imposed by the weight of the
home, including its contents and any exterior loads, such as those imposed by snow. Because the forces associated
with flooding, wind, and earthquakes can impose horizontal loads, piers used in retrofitting must be adequately
reinforced with properly sized and placed steel bars. The connections between the piers and the original founda-
tion and elevated home also must be able to resist the expected horizontal and vertical loads on the home so the
home does not shift off the foundation.
NOTE
Open foundations are required for ele-
vations in Coastal High Hazard Areas
(Zones V, VE, and V1–V30) and are
recommended for elevations in river-
ine floodplains where flow velocities
are greater than 5 fps.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-21
ELEVATING YOUR HOME 5
Figure 5-13a through 5-13d.
Elevating a basement or
crawlspace foundation home
on piers.
5-13a
5-13b 5-13c
5-13d
5-22 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
5 ELEVATING YOUR HOME
Posts or Columns
For posts or columns, the home elevation process is the same as that described for piers; however, the existing
foundation usually must be removed so that the posts or columns and their concrete encasements or pads can be
installed. Posts are usually placed in drilled or excavated holes. Each post or column is either encased in concrete
or anchored to a concrete footing.
Figure 5-14 shows a home elevated on two types of post or column foundations. Because an elevated house sits
higher off the ground on a slender foundation, the lateral (sideways) loading on the house becomes a more im-
portant factor than a house sitting only a few feet off the ground on a continuous foundation. Large lateral loads
can be exerted on the house by forces such as wind, earthquakes, or floodwaters. Simple wooden posts will not
likely be able to resist these lateral loads and would require a formal design by a structural engineer. Lateral brac-
ing can be used to prevent movement of the building for occupant comfort, but it should not be used to provide
lateral support to prevent foundation failure. Additionally, bracing in two directions is only recommended in areas
of low velocity flooding—areas with high-velocity flooding should only be braced in one direction (as shown in
Figure 5-14). Depending on the potential lateral loads that the house must resist, a metal framing system may be
a more practical approach than simple wooden posts. This system may also require an extensive concrete footing
system so that the loads can be transferred down the posts or columns and into the ground. Although this eleva-
tion technique may appear simple, you should retain the services of a structural engineer who understands how
loads are transferred.
Figure 5-14. Home elevated on post or column foundations.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-23
ELEVATING YOUR HOME 5
Piles
Elevating on piles is a more involved process than elevating on piers, posts, and columns. Piles are usually driven
or vibrated into the ground or jetted in with a high-pressure stream of water. They are not supported by concrete
footings or pads. Unlike the construction of wall, pier, or post or column foundations, the pile-driving operation,
which requires bulky, heavy construction machinery, cannot be carried out under a home that has been lifted on
jacks. Instead, the home is usually lifted and moved aside until the piles have been installed. Because the existing
foundation is not used, it must be removed. Figure 5-15 shows a home elevated on a pile foundation.
More information on elevating homes on open foundations can be found in Hurricane Sandy Fact Sheet No. 2,
Foundation Requirements and Recommendations for Elevated Homes (FEMA. 2013c). This fact sheet addresses many of the com-
mon issues associated with elevating homes on open foundations, and also addresses elevating a home on an open
foundation that is confined by narrow lot lines.
Figure 5-15. Home elevated
on piles.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-1
6.0 Relocation and Demolition
This chapter describes two mitigation alternatives: relocation and demolition.
Relocation Demolition
These mitigation options can be more effective than other mitigation methods because they provide the opportu-
nity to relocate or rebuild in an area outside of the floodplain. If rebuilding outside the floodplain is not possible,
then moving to less vulnerable locations (i.e., from Zone V to a Zone A) on the same property or on a new proper-
ty is also an option. If neither rebuilding outside the floodplain or in a less vulnerable location is feasible, elevation
may be your best option. Elevation is described in detail in Chapter 5. This chapter addresses relocation outside
of the floodplain.
Because relocation and demolition are both complex, you
should consult design and/or construction professionals to help
with your mitigation project.
NOTE
Always use a licensed, bonded, and
insured contractor for relocation pro-
jects. Be sure that your contractor has
experience with relocation projects
and understands the considerations
discussed in Section 6.1.1. Checking
the contractor’s references is very
important.
For information about home relocation
companies, contact the International
Association of Structural Movers at
P.O. Box 2104, Neenah, WI 54956-
2104 (803) 951-9304, http://www.
iasm.org/.
6.1 Relocation
Relocation, or moving your home out of the flood
hazard area, offers the best protection from flooding. It
also can free you from anxiety about future floods and
lower your flood insurance premiums. However, relo-
cation usually is the most expensive of the retrofitting methods.
The relocation process involves lifting a home off its founda-
tion, placing it on a heavy-duty flatbed trailer, hauling it to a
new site outside the flood hazard area, and lowering it onto a
new conventional foundation. The process sounds straightfor-
ward, but a number of considerations require careful planning.
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6.1.1 Considerations
Condition of Home
For a home to be picked up and moved successfully, it must be structurally sound. All the structural members and
their connections must be able to withstand the stresses imposed when the home is lifted and moved. Before the
home is lifted, the home moving contractor must inspect it to verify its structural soundness. A home that is in
poor condition, especially one that has been damaged by flooding, may need so much structural repair and brac-
ing that relocation is not be practical (see Section 6.2 for demolition).
Home Size, Design, and Shape
In general, the types of homes that are the easiest to elevate (as discussed in Section 5.1.5) are also the easiest
to relocate: single-story, wood-frame homes over a crawlspace or basement foundation, especially those with a
simple rectangular shape. These homes are relatively light, and their foundation design allows the home moving
contractor to install lifting equipment with relative ease. Multistory homes and solid masonry homes are more
difficult to relocate because their greater size and weight requires additional lifting equipment and makes them
more difficult to stabilize during the move. Slab-on-grade foundations complicate the relocation process because
they make the installation of lifting more difficult.
The relocation process is also more complicated for homes with
brick or stone veneer, which can crack and peel off when dis-
turbed. Removing the veneer before the home is moved and
replacing it once the home is on the new foundation at the new
site may be less expensive. For the same reason, chimneys may
need to be removed before the move and rebuilt afterwards.
If they are to be moved with the home, they must be braced
extensively.
Moving Route Between Old and New Sites
Restrictions along the route to the new site can complicate a
relocation project, especially for large homes. Narrow roads, re-
strictive load capacities on roads and bridges, and low clearances
under bridges and power lines can make finding an alternative
route necessary. When no practical alternatives are available, the
home moving contractor may have to cut the home into sec-
tions, move them separately, and reassemble the home at the
new site. Experienced home movers can make the cuts and re-
assemble the home in such a way that it will not appear to have
ever been apart.
Disruption of Occupants
Among all the retrofitting methods, relocation is the most dis-
ruptive for the occupants of the home. Before the home can be
lifted, all utility systems must be disconnected, and the home
becomes uninhabitable. You cannot move back into the home
until it has been installed at the new site and all utility systems
NOTE
Relocation is sometimes used as an
alternative to demolition (as described
in Section 6.2) when a home has been
damaged. Instead of demolishing the
home, the owner may be able to sell
it for salvage to a contractor, who will
then move the home to another site,
renovate it, and sell it. Relocation is
also used after a community acquires
a flood-prone property from the own-
er. Instead of leaving the home to be
demolished, the owner may decide to
keep the home and move it to proper-
ty outside the flood hazard area.
CROSS REFERENCE
See Section 4.1.3 for information
about working with local officials
regarding flood hazards and permit-
ting requirements in your community.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-3
RELOCATION AND DEMOLITION 6
reconnected. In the interim, you will need temporary lodgings and a place to store your furniture and other
belongings.
6.1.2 The Relocation Process
The relocation process consists of more than lifting and moving the home. You must work with your contractor
to select a new site for the home, and the contractor must plan the moving route, obtain the necessary permits,
prepare the new site, and restore the old site.
Selecting the New Site
Selecting a new site for your relocated home is similar to select-
ing a site on which to build a new home. You need to consider
the following:
Natural Hazards – Remember that the goal of relocating is to
move your home to a site that will be safe from flooding and
other natural hazards. Before buying new property, check with
local officials about the flood, wind, and earthquake hazards at
any new site you may be considering (see Section 4.1.3).
Utilities – Determine what steps you need to take to install new
utility systems and to have utility lines extended to your new
site. Consider electrical, gas, water and sewer, telephone, and ca-
ble TV services. Your community will probably require that your
new utility systems meet current code requirements. Regardless
of these requirements, you should consider upgrading one or
more of your utility systems to provide more energy-efficient
service.
Accessibility – Your new site must be accessible to the home movers and to the construction crews that will pre-
pare the site and build the new foundation for your home. The more difficult it is for contractors to reach and
work at your new site, the more expensive your relocation project is likely to be. If extensive grading and clearing
are necessary for adequate access, some of the characteristics that made the site attractive to you may be dimin-
ished. Your existing site may also present some accessibility issues if your home has a cistern or septic tank system
installed on the property. If these need to be detached from your home and installed at the new project site, ad-
ditional time and cost may be involved.
Another important consideration regarding accessibility is the difficulty of moving the home to the new site.
In determining the best route between the old and new sites, the moving contractor must anticipate potential
problems. For example, the routing of the home may be impeded by narrow bridges and road cuts, bridges with
low weight limits, low-hanging utility lines and traffic signals, low underpasses, tight turns, road signs, and fire
hydrants.
The moving contractor should also coordinate any special services that may be required to deal with obstacles,
such as raising traffic lights, relocating signs, and constructing temporary bridges. Utility lines can usually be
raised temporarily during the move, but utility companies often charge for this service. In some cases, it may be
possible to avoid some obstacles by choosing an overland (non-road) travel route.
WARNING
Regardless of the age of your home,
you may be required by local regu-
lations to bring it up to current code
when you move it to a new site. This
requirement could affect not only the
home but also its utility systems. You
should check with your local officials
about such requirements before you
decide to relocate.
6-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
6 RELOCATION AND DEMOLITION
Permitting
You or your moving contractor must obtain permits to move the home on public roads or other rights-of-way.
These permits may be required by local governments, highway departments, and utility companies, not only in
the jurisdiction from which your home is being moved, but also any jurisdiction through which the home will
pass. If the moving route crosses or affects private land, you may need to obtain the approval of the landowner.
Obtaining the necessary permits and approvals may be a lengthy and complex process, and you may find that the
requirements vary from jurisdiction to jurisdiction and agency to agency. So it is extremely important that you,
your design professional, and your moving contractor investigate the need for permits and approvals before you
make a final decision to relocate.
You or your design professional should check with local officials to make sure that, when your home is moved to
the new site, it will conform to all zoning requirements and building codes in effect at the time of the relocation.
The design professional should also determine the local design standards and permitting requirements that govern
the development of your new site. All permits required for construction at the new site, moving your home, and
restoring the old site after the home is moved should be obtained before the relocation project begins.
Preparing the New Site
Before the home is moved, the new foundation must be de-
signed and is usually partially constructed. The foundation will
be completed after the home is brought to the site. Clearing,
excavation, and grading are necessary to allow construction
to begin and to ensure that the home can be maneuvered on
the site. Also, unless already available, utility service must be
brought into the site so that there will be no delay in connect-
ing them to the home and making it habitable. Figure 6-1 shows
a new slab-on-grade foundation that is being constructed for a
relocation project.
CROSS REFERENCE
Refer to Section 5.2 for a description of
how homes on various types of foun-
dations are lifted off their foundations.
Figure 6-1. New foundation
is being prepared (photo
courtesy of Wolfe House
Movers).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-5
RELOCATION AND DEMOLITION 6
Lifting the Home
In general, the steps required to lift a home off its foundation are the same as those described in Section 5.2.1 for
elevating a home on extended foundation walls. As described in Section 5.2.2, the steps to lift homes on basement
and crawlspace foundations differ from those for homes on slab-on-grade foundations.
Homes on basement and crawlspace foundations are separated from their foundations and lifted on steel I-beams
that pass through the foundation walls directly below the floor framing. The lifting is done with hydraulic jacks
placed directly under the I-beams. The process for homes on slab-on-grade foundations is similar. However, be-
cause these homes are lifted with the concrete floor slab attached, the I-beams are inserted below the slab. Figures
6-2 through 6-5 show the basic steps for lifting a home.
Figure 6-2. Clearing
pathways beneath the
structure for lifting supports
(photo courtesy of Wolfe
House Movers).
6-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
6 RELOCATION AND DEMOLITION
Figure 6-3. Pathways for
lifting beams (photo courtesy
of Wolfe House Movers).
Figure 6-4. Beams supported
by cribbing are placed at
critical lift points (photo
courtesy of Wolfe House
Movers).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-7
RELOCATION AND DEMOLITION 6
Figure 6-5. Hydraulic jacks
lift the structure, and the
home is separated from
existing foundation (photo
courtesy of Wolfe House
Movers).
Moving the Home
After the home is lifted, the moving contractor performs the grading and excavation necessary to create a tempo-
rary roadway that will allow the home to be moved to the street. The area beneath the home must be leveled and
compacted so that trailer wheel sets can be placed under the home (Figure 6-6). The wheel sets and lifting beams
form the trailer on which the home will be moved.
Figure 6-6. Trailer wheel sets
are placed beneath the lifting
beams (photo courtesy of
Wolfe House Movers).
6-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
6 RELOCATION AND DEMOLITION
After the wheels are attached, a tractor or bulldozer tows the home to the street. As the home is being moved,
workers continually block the wheels to prevent sudden movement. At the street, the home is stabilized, the trailer
is attached to a truck, and the move to the new site begins (Figure 6-7).
Figure 6-7. The move to
the new site begins (photo
courtesy of Wolfe House
Movers).
At the new site, the moving contractor positions the home over the partially completed foundation and supports
the home on cribbing so the trailer wheels can be removed. As in the home elevation process described in Chapter
5, the home is lifted on hydraulic jacks to the desired height and the foundation is completed below it. The home
is then lowered onto the foundation, all utilities are connected, and any necessary backfilling and landscaping is
completed (Figure 6-8).
Figure 6-8. House is
lowered and connected
to the foundation after
the foundation is fully
constructed (photo courtesy
of Wolfe House Movers).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-9
RELOCATION AND DEMOLITION 6
Restoring the Old Site
After the home is moved, the old site must be restored accord-
ing to the local regulations. Restoring the site usually involves
demolishing and removing the old foundation and any pave-
ment, such as a driveway or patio; backfilling an old basement;
removing all abandoned utility systems; grading to restore areas
disturbed by demolition; and stabilizing the site with new veg-
etation. Permits are normally required for demolition, grading,
and vegetative stabilization.
If your old site included a septic tank or fuel storage tank, you
may have to meet the requirements of environmental regulations
aimed at preventing contamination of groundwater. Depending
on the age and condition of the tank, you may be required to
drain and remove it. If it is an underground tank, you may have
to drain it and anchor it to prevent flotation. You may also be
required to test the soil around an underground fuel tank to
determine whether leakage has occurred. As the homeowner,
you will usually be responsible for cleaning contaminated soil if
there has been any leakage from the tank. In this situation, you
will need the services of a qualified geotechnical or environ-
mental engineer.
Local utility companies or regulatory officials can inform you
about requirements concerning capping, abandoning, or re-
moving various utility system components.
6.2 Demolition
Demolition is tearing down a damaged home and either rebuilding a compliant home on the same
property, rebuilding a compliant home on new property, or moving into another structure. This
retrofitting method may be the most practical of all those described in this guide when a home has sus-
tained extensive damage, especially severe structural damage.
If a flood-prone home has been severely damaged, because of
flooding or any other cause, demolition can be practical and
effective. Demolition may also be practical for an undamaged
home that, because of deterioration over time or for other rea-
sons, is not worth retrofitting with any of the other methods
described in this guide. If you choose demolition, you will tear
down your damaged home and either rebuild a compliant home
on the same property or elsewhere outside the floodplain. If you
decide not to rebuild, your State or local government may buy
or acquire your property. Depending on your choice of a site
for your new home, this method can lower or even eliminate
your flood insurance premiums. If you decide to rebuild, your
NOTE
Always use a licensed, bonded, and
insured contractor for demolition
projects and for reconstruction proj-
ects. Be sure that your contractor has
experience with demolition (and con-
struction for mitigation reconstruction)
and understands the considerations
discussed in Section 6.2.1.
NOTE
Many homeowners have sold or
deeded vacated flood-prone proper-
ties to local municipalities for use as
parkland or open space.
DEFINITION
Acquisition is the process by which
your State or local government pur-
chases your flood-prone property,
demolishes the building, and main-
tains the land as an open space.
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6 RELOCATION AND DEMOLITION
mitigation reconstruction project may be eligible for FEMA
grant money (see Section 2.6.1).
The demolition process involves disconnecting and capping
utility lines at the damaged home, tearing the home down,
removing debris and otherwise restoring the old site, and build-
ing or buying a new home. The most important considerations
relate to how badly your home has been damaged and your op-
tions of building or buying a new home.
6.2.1 Considerations
Amount of Damage
Demolition is more practical for severely damaged homes than for those with little or no damage. If a flood, fire,
earthquake, hurricane, or other disaster has caused extensive damage to the interior and exterior of your home
or left it structurally unsound, you will probably find that demolishing the home and rebuilding it is easier than
making all of the necessary repairs. Also, remember that a severely damaged home in the regulatory floodplain will
almost surely be considered Substantially Damaged under your community’s floodplain management ordinance,
regulation, or provisions of the building code. Salvaging such a home would require repairing the damage and
elevating the home (including backfilling a basement); wet floodproofing areas used only for parking, building
access, or storage; or relocating the home as described in Section 6.1.
Rebuilding or Buying Another Home
After demolishing your home, you may buy or build a home elsewhere or, in some cases, rebuild on your existing
property at an elevation above the BFE. Regardless of your decision, your goal is to greatly reduce or eliminate the
potential for damage from floods, earthquakes, high winds, and other hazards. If you buy or build a home else-
where, you’ll want to find a site that is outside the regulatory floodplain, ideally one that is well above the BFE. You
should also check with your local officials about other hazards before you make your final decision.
If you demolish your existing house and plan to relocate elsewhere, you will need to think about what to do with
the existing property (land). Property that is entirely within the regulatory floodplain may be difficult to sell be-
cause of restrictions on its use. Your community may be interested in acquiring your property and then converting
it to a public use, open space area. If you receive a FEMA grant to buy out your property then the land will most
likely be deeded to the community and its use will be restricted to open space. As explained in Section 2.6, some
Federal programs provide grants to States and communities that they can use to buy flood-prone homes and prop-
erties. State and local programs may also provide financial assistance. Check with your local officials about these
programs.
When buying or building a home elsewhere is too expensive, you may be able to rebuild on your existing prop-
erty, either on the site of your old home or, preferably, on a portion of your property that is outside the regulatory
floodplain. If you rebuild on the site of your old home, your community’s floodplain management ordinance,
regulation, or provisions of the building code will require that the lowest floor be at or above the BFE. How you
meet this requirement depends on the flood zone and code requirements of your community. An important dis-
advantage of this approach is that you may not have access to your home during floods.
If your existing property includes a large enough area outside the regulatory floodplain, a better choice is to re-
build there. Building outside the floodplain gives you greater freedom to build the type of home you want. Also,
DEFINITION
Mitigation reconstruction is the
construction of an improved, elevat-
ed building on the same site where
an existing building and/or foundation
has been demolished.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-11
RELOCATION AND DEMOLITION 6
because both the home and property are outside the floodplain, restricted access during flooding is less likely
to be a problem. Remember that floods do not follow the lines on FIRMs, so although building outside of the
floodplain may not involve insurance implications, building high is safer and smarter. Property owners outside of
high-risk flood areas file over 20 percent of NFIP claims and receive one-third of disaster assistance for flooding.
Disruption of Occupants
Like relocation, demolition can be disruptive for the occupants of the home. Unless you decide to buy an existing
home elsewhere, you must find a place to live and to store your furniture and belongings while your new home
is being built.
Permitting
You or your design professional or contractor must check with local officials regarding permitting requirements
for the necessary work. All permits for demolition should be obtained before the demolition process begins, in-
cluding disconnecting and capping utilities, disposing of debris, new construction, and restoration of the old site.
6.2.2 The Demolition Process
Tearing Down the Old Home
Your utility companies must first turn off all services to the home. Your demolition contractor will then discon-
nect the utility lines. If you do not plan to rebuild on the same site, the contractor will cap the lines permanently
or remove them according to the requirements of the utility companies. Before demolition begins, environmen-
tal hazards, such as asbestos, must be abated in accordance with Federal, State, and local requirements. Typically,
the demolition contractor will bulldoze the home and then dispose of the resulting debris as required by Federal,
State, and local regulations.
Restoring the Old Site
If you are not rebuilding on the old site, it must be restored according to the requirements of local regulations.
Site restoration usually involves demolishing and removing not only the home, but also any pavement, such as a
driveway or patio; grading to restore areas disturbed by the demolition; and stabilizing the site with grass.
If your old site included a septic tank or fuel storage tank, you may have to meet the requirements of environ-
mental regulations aimed at preventing contamination of groundwater. You may be required to drain and remove
aboveground and underground storage tanks, or you may have to anchor them to resist flotation. You may also be
required to test the soil around an underground tank to determine whether leakage has occurred. As the home-
owner, you will usually be responsible for cleaning contaminated soil if there has been any leakage from the tank.
In this situation, you will need the services of a qualified geotechnical or environmental engineering firm.
Local utility companies or regulatory officials can inform you about requirements concerning capping, abandon-
ing, or removing various utility system components.
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Rebuilding – Mitigation Reconstruction
Your construction contractor will prepare the site and build
your new home according to the local building code, flood-
plain management, and zoning requirements. The lowest floor
of your new home must be at or above the BFE, so your new
home cannot include a basement. Figure 6-9 shows a mitigation
reconstruction project that was recently completed in Louisiana
following Hurricane Katrina.
Depending on where you decide to rebuild, local util-
ity companies may have to extend new lines onto the site
of your new home. This is usually done before construc-
tion is completed and your contractor will hook up the
utility lines as part of construction. You may need the services of a design professional if specialized utility
systems are required because of the location of your site, the type of home you decide to build, or the nature of
the hazards at the site.
WARNING
If you rebuild on the site of your old
home, your community’s floodplain
management ordinance, regulation,
or provisions of the building code will
not allow you to have a basement be-
low the BFE.
Figure 6-9. Typical mitigation
reconstruction project.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 7-1
7.0 Floodproofing
This guide describes two types of floodproofing: wet and dry. As
its name implies, wet floodproofing allows floodwaters to en-
ter the enclosed areas of a home. In contrast, dry floodproofing
prevents the entry of floodwaters. Because both approaches rely
on varying philosophies of managing flood waters, this chapter
separates the approaches and mitigation methods.
7.1 Wet Floodproofing
The benefit of wet floodproofing is that, if floodwaters
are allowed to enter the enclosed areas of the home
and to quickly reach the same level as the floodwaters
outside, the effects of hydrostatic pressure, including
buoyancy, are greatly reduced. As a result, there are equalized
loads imposed on the home during a flood and the likelihood
of structural damage may be greatly reduced. Wet floodproofing
is generally used to limit damages to enclosures below elevated
buildings, walkout-on-grade basements, below-grade base-
ments, crawlspaces, or attached garages. It is not practical for
these areas to be used as living space, and, if the home is being
Substantially Improved or has been Substantially Damaged, wet
floodproofing can lead to NFIP compliance only if (1) the area
is limited to parking, access, or storage, (2) designed to allow
for automatic entry and exit of flood waters through the use of
flood openings, and (3) uses only flood damage-resistant mate-
rials below the DFE.
Successful wet floodproofing involves the following:
n Ensuring that floodwaters enter and exit the home’s
enclosed area (for NFIP compliance, floodwaters must
exit the enclosed area automatically, without the use of
pumps)
WARNING
If your home is being Substantially
Improved or has been Substantially
Damaged, your community’s flood-
plain management ordinance or
regulations will restrict the use of wet
floodproofing to attached garages and
enclosed areas below the BFE that
are used solely for parking, building
access, or storage. For more informa-
tion, refer to NFIP Technical Bulletin
7, Wet Floodproofing Requirements
(1993).
WARNING
Non-compliant wet floodproofing a
residence will not reduce the flood in-
surance premium.
NOTE
Flood damage-resistant materials are
discussed later in this chapter.
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n Ensuring that floodwaters inside the home rise and fall at the same rate as floodwaters outside the home
n Reducing damage caused by contact with floodwaters to areas of the home that are below the flood level
n Protecting service equipment inside and outside the home
n Relocating high-value contents stored below the DFE
This chapter describes the modifications that must be made to a home as part of a wet floodproofing project and
the most important considerations for this retrofitting method. Protection of service equipment is discussed in
Chapter 9.
7.1.1 Design Flood Elevation
All construction and finish materials in the areas of the home that
will be allowed to flood should be resistant to damage caused by
direct, and possibly prolonged, contact with flood-water. Areas
used for living space typically contain floor and wall coverings
and other finishing materials, furniture, appliances, and items
that could be easily damaged by floodwater and expensive to
clean, repair, or replace. Therefore, wet floodproofing is practical
only for portions of a home that are not used for living space,
such as a basement, walkout-on-grade basement, crawlspace,
non-air-conditioned porch, or attached garage. As shown
in Figure 7-1, the lowest floor should be at or above the DFE
(including freeboard) for wet floodproofing.
If your DFE is above the elevation of your lowest finished floor, you should consider one or more of the other ret-
rofitting methods described in this guide, such as elevation (Chapter 5). As you review Chapter 5, note that most
of the elevation methods incorporate the principles of wet floodproofing. Elevation raises the living space above
the flood level and allows floodwaters to enter the enclosed areas of the home below the living space if those areas
have been retrofitted for compliance.
7.1.2 Hazards
Wet floodproofing protects a home from the effects of hydrostatic pressure but not from other flood hazards, such
as the hydrodynamic force of flowing water, erosion and scour, saturation of building elements, damage to con-
tents, the impact of ice and other floodborne debris, and damage from floodborne contaminants. If you have seen
evidence of these hazards in past floods in your area, or if your community officials confirm that your home may
be affected by these hazards, you should consider an alternative retrofitting method, such as relocation (Chapter
6) or elevation on an open foundation (Chapter 5). Wet floodproofing a home does not change its vulnerability
to damage from high winds or earthquakes.
NOTE
Always consult a licensed, bonded,
and insured contractor before initi-
ating a wet floodproofing project. Be
sure that your contractor has expe-
rience with wet floodproofing and
understands the considerations dis-
cussed in Section 7.1.
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FLOODPROOFING 7
7.1.3 Post-Flood Cleanup
Remember that floodwater is rarely clean and may pose other
safety hazards to occupants and contractors. Use caution when
entering a recently flooded home; watch for structural instabil-
ity or shifted contents as well as displaced animals. There are
three important principles to follow when you first return to a
flooded home before beginning repairs:
1. Personal Safety
Flooded buildings pose a number of health and safety risks, for
both individuals who wish to maintain occupancy and those
who work to repair the buildings. Eliminating hazards is the
best way to protect occupants and workers; until conditions can
NOTE
If more than 10 square feet are af-
fected by mold, you should contact a
mold cleanup professional. For more
information about mold prevention
and remediation, visit the Center for
Disease Control’s (CDC’s) mold Web
site at http://www.cdc.gov/mold.
Figure 7-1. Typical wet
floodproofing.
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7 FLOODPROOFING
be returned to normal, anyone working in a flooded building should use appropriate personal safety equipment
and take appropriate safety precautions.
Mold: The Occupational Safety and Health Administration (OSHA) Fact Sheet, Hurricane Sandy Cleanup PPE Matrix
(OSHA-FS-3612, 2012), provides information on personal protective equipment. Anyone entering a house with
visible mold growth should wear a disposable suit, rubber gloves or other hand protection, and respiratory protec-
tion. The OSHA Fact Sheet, Mold Hazards During Hurricane Sandy Cleanup (OSHA-FS-3619, 2012), provides information
on mold.
Asbestos and Lead Paint: Asbestos in floor tile, pipe and boiler installation, and electrical wiring is common in
many homes built before 1980. Breathing asbestos fibers released from building products can increase the risk of
cancer and cause a number of serious lung diseases. Paint in homes constructed prior to 1978 may contain lead.
If asbestos or lead paint is suspected, obtain the services of a specialist to perform material testing, and do not
disturb the material until testing has been completed. If testing confirms the presence of lead, remediation should
be conducted by a licensed professional in accordance with State and Federal regulations.
2. Cleaning Flood Damaged Homes to Prepare for Repair and Reconstruction
All objects that came into contact with the floodwater should be
cleaned and sanitized. Water-damaged porous materials are dif-
ficult to properly clean and should be discarded.
Move out: Remove salvageable contents that were not affected
by the water; dispose of all saturated porous materials, such as
mattresses or upholstery.
Tear out: Remove all water-damaged interior finishes, includ-
ing wet carpet and padding, curled vinyl tiles and linoleum,
saturated drywall and plaster, saturated wall insulation, flooded
electrical receptacles, and swollen wall paneling.
Barriers: Place plastic barriers between affected and unaffected
areas of the building (typically between the first and second
floors at the base of the stairs) to reduce the potential of mold
spores spreading to unaffected areas.
Application of Cleaners: Cleaners are most efficiently applied using a combination of foam cleaning processes
and brush cleaning, followed by pressure washing. Foam cleaning processes allow the product to stay on the
surface long enough for the chemicals to kill the mold or bacteria and makes drying easier. Brushes improve de-
contamination of wooden studs and other surfaces by scrubbing the foam into affected surfaces. Water-damaged
porous materials should be removed. Care should be taken to inspect both the front and back side of the non-
flooded gypsum wall board and plaster walls for remaining dirt and mold to ensure all affected areas are cleaned.
Pressure Washing: The fastest and most efficient rinse tool, which minimizes the amount of water used to re-
move residual foam from wall studs, floor joists, and other surfaces, is a residential-type pressure washer set at low
pressure so that the spray is a light mist.
WARNING
Although bleach is an inexpensive
and convenient cleaning agent, it has
many serious drawbacks when used
to clean flood-impacted materials. It is
not effective on porous materials, such
as gypsum wall board or as a disin-
fectant on surfaces with residual dirt
and can corrode electrical and metal
components of mechanical systems.
Do NOT combine chlorine bleach
and ammonia, as the combination of
chemicals will release vapors that can
be extremely toxic or even fatal.
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Cleaning Crawlspaces: Removing the flooring is the simplest way to enter crawlspaces to decontaminate these
areas. Solid contaminants should be removed from under the building, along with any remaining water. All ex-
posed sides of floor joists, foundation walls, and remaining structural elements should be cleaned with cleaning
foam and brushing.
Cleaning in Weather Extremes: Although cold weather pos-
es challenges for restoring flooded buildings, it also has some
advantages. Cooler weather slows down the spread of mold.
However, buildings need to be warmed to 50° to 75°F to pro-
vide for worker comfort, improve the effectiveness of cleaning
and sanitizing agents, and allow commercial drying equipment
to operate efficiently. Mold and bacteria spread more quickly in
hot and humid weather, slowing natural drying of flooded and
contaminated building elements; in such circumstances, the use
of drying equipment is critical to lower the moisture content of
structural materials prior to rebuilding or repair.
3. Proper Drying Prior to Rebuilding
After the cleaning process has been completed, the building
and any salvageable contents need to dry. Failure to allow ad-
equate drying prior to reconstruction can trap moisture in the
building, which can cause fungal growth and potential health
problems. Once the electrical and HVAC systems have been re-
stored and sanitized, the moisture content of wetted salvageable
building materials should be checked to determine whether
drying equipment, such as fans and dehumidifiers, is necessary.
For more information about restoring flooded buildings or ini-
tial precautions to be taken when entering flooded buildings,
refer to the Hurricane Sandy Recovery Fact Sheet Number 1,
Cleaning Flooded Buildings (FEMA. 2013a)1.
FEMA P-942, Hurricane Sandy in New Jersey and New York (FEMA. 2013d) provides a comprehensive assessment of build-
ing material performance and mitigation actions appropriate to flooded homes, other structures, and infrastructure.
7.1.4 Modifications Required for Wet Floodproofing
Wet floodproofing requires a variety of modifications to your home, including its walls, construction and finish-
ing materials, and service equipment. Consult with a design professional or licensed contractor before you make
any modifications.
7.1.5 Installing Openings
The most important part of a wet floodproofing project is installing wall openings that allow the entry and exit of
floodwaters. The openings must be installed in foundation walls and in garage walls as appropriate, below the ex-
pected flood level (Figure 7-2). The goal is not simply to allow the entry and exit of floodwaters, but also to ensure
1 The fact sheet is part of FEMA’s Hurricane Sandy Recovery Advisory and Fact Sheet technical series and can be downloaded at
http://www.fema.gov/hurricane-sandy-building-science-activities-resources
CROSS REFERENCE
For more information about openings
requirements for wet floodproofing,
refer to NFIP Technical Bulletin 1,
Openings in Foundation Walls and
Walls of Enclosures (2008), and
FEMA P-259, Engineering Principles
and Practices for Retrofitting Flood-
Prone Residential Structures (FEMA.
2012a).
WARNING
Failure to allow adequate drying prior
to reconstruction can trap moisture in
the building, which can cause future
fungal growth and potential health
problems.
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that the water level inside the home rises and falls at roughly
the same rate as the water level outside so that hydrostatic pres-
sures inside and outside are continuously equalized. As shown
in Figure 7-2, large differences in the interior and exterior wa-
ter levels allow unequalized hydrostatic pressures and, therefore,
defeat the purpose of wet floodproofing. Figure 7-3 illustrates
typical enclosures with flood openings.
For equal water levels to be maintained, both the size and num-
ber of openings must be adequate. Otherwise, when floodwaters
are rising and falling, water will not be able to flow into or out
of the home fast enough. The number of openings required and
their size will depend on the rate of rise and the rate of fall of
the floodwaters (see Chapter 2) and on the size of the area that
is being allowed to flood. In general, the faster the rates of rise
and fall and the larger the flooded area within the home, the
greater the number and size of openings required.
NOTE
If you cover wall openings with lou-
vers or screens, keep in mind that,
the more restrictive they are, the more
likely they are to become clogged
with debris during floods and prevent
the flow of floodwaters. Make sure
that any screens or louvers allow the
passage of water that contains sus-
pended sediment and other small
debris. After floodwaters have re-
ceded, screens and louvers must be
cleaned of any debris that may have
accumulated.
Figure 7-2. Wall openings
must allow floodwaters not
only to enter the home, but
also to rise and fall at the
same rate as floodwaters
outside the home.
Figure 7-3. Sketch of foundation plan of home with multiple enclosed areas, each with flood openings. Typical enclosures
with flood openings (Left). Flood opening in typical crawlspace foundation (Right).
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FLOODPROOFING 7
If you are wet floodproofing areas below the BFE in a Substantially Improved or Substantially Damaged home,
your community’s floodplain management ordinance or regulation will require you to install openings in the ex-
terior walls of all enclosed areas below the BFE (see Section 3.1.1). The minimum requirements are:
n You must provide at least two wall openings for each enclosed area—one in each of two different walls.
In other words, you cannot put both openings in the same wall.
n If your home has more than one enclosed area, you must install openings in the exterior walls of each enclosed
area so that floodwaters can enter directly from the outside.
n The total area (size) of all openings for each enclosed area must equal at least 1 square inch for every
square foot of floor space in the enclosed area. For example, if the enclosed area is 25 feet by 40 feet
(1,000 square feet), the total net area of the openings must be at least 1,000 square inches, or roughly
7 square feet. In this example, you could meet the size requirement by providing two 3½-square-foot
openings or several smaller openings whose total net area equals 7 square feet.
n The bottom of each opening must be no higher than 1 foot above the higher of the exterior grade or
interior grade directly below the opening.
n Floodwaters must be able to flow in and out of enclosed areas automatically. If you place louvers, screens,
or other types of covers over the openings (which many homeowners do to prevent animals from
entering the enclosed areas), they must not block the flow of water. Note that the area of any screens
or louvers covering the openings must be subtracted from the gross opening area. Because the need
for human intervention reduces the reliability of wet floodproofing, you may not install any type of
electrical-, mechanical-, or manual-operated cover.
n Flood openings must be entirely below the BFE.
FEMA developed these requirements to provide homeowners with a straightforward means of determining where
and how to install wall openings without the aid of an engineer or design professional. The requirements provide
a margin of safety for wet floodproofed homes subject to flooding with rates of rise and fall as high as 5 feet per
hour. If you wish to install openings that do not meet one or more of the requirements listed above, your de-
sign must be certified by a registered engineer or other licensed design professional and approved by your local
officials. See FEMA’s NFIP Technical Bulletin 1, Openings in Foundation Walls and Walls of Enclosures (2008), for more in-
formation about openings requirements.
7.1.6 Protecting the Underside of Elevated Buildings
The undersides of elevated coastal buildings are typically covered with vinyl or aluminum soffits or plywood
sheathing to protect insulation and metal floor system connectors. The undersides of these buildings are often
damaged by high hurricane force winds, allowing water to be driven into the building. Lost paneling or sheath-
ing can become wind-borne debris, increasing the risk of damage. How the space below the building is designed
and built is determined by local floodplain regulations and building codes, which may include fire resistant-rated
building materials, depending on the use of the underneath space (parking, storage areas).
Underside materials should meet flood damage-resistant requirements outlined in NFIP Technical Bulletin 2, Flood
Damage-Resistant Materials Requirements (2008), and local code requirements, including fire resistance requirements
where applicable. In coastal areas, make sure to use corrosion-resistant fasteners to secure the underside materials.
Wind loads based on wind speed maps for the area where the building is located must be included in the under-
building wind protection assembly design. To ensure the assembly is effective, a licensed engineer or architect
should prepare the design in accordance with Hurricane Isaac Recovery Advisory 1 (see Cross Reference).
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7.1.7 Using Flood Damage-Resistant Materials
In the areas below the anticipated flood level, any construction
and finishing materials that could be damaged by floodwaters
must be either removed or replaced with flood damage-resistant
materials as required by your community’s floodplain manage-
ment ordinance or regulations. Vulnerable materials include
gypsum wall board (also called dry wall), blown-in and fiber-
glass batt insulation, carpeting, and non-pressure-treated wood
and plywood. Flood damage-resistant materials are those that
can be inundated by floodwaters with little or no damage. They
include such materials as concrete, stone, masonry block, ce-
ramic and clay tile, pressure-treated and naturally decay-resistant
lumber, epoxy-based paints, and metal. In addition to resisting
damage from floodwaters and their contaminants, these materi-
als are relatively easy to clean after floodwaters recede.
Table 7-1 lists materials that are acceptable and unacceptable
for use in wet floodproofing projects. NFIP Technical Bulletin
2, Flood Damage-Resistant Materials Requirements (2008), offers more
complete guidance on materials that can and cannot be used to
wet floodproof an area below the DFE. Consult a design profes-
sional before selecting materials to wet floodproof any areas in
your home.
CROSS REFERENCE
For more information about flood dam-
age-resistant materials, refer to NFIP
Technical Bulletin 2, Flood Damage-
Resistant Materials Requirements
(2008). This bulletin includes a de-
tailed list of common floor, wall, and
ceiling materials categorized accord-
ing to their applicability for use in areas
subject to inundation by floodwaters.
CROSS REFERENCE
For more information about openings
protecting the underside of elevat-
ed buildings, refer to Hurricane Isaac
Recovery Advisory 1, Minimizing
Wind and Water Intrusion by Covering
the Underside of Buildings (FEMA.
2012c).
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FLOODPROOFING 7
Table 7-1. Flood Damage-Resistant Materials
Material Type Acceptable Unacceptable
Structural Flooring Materials • Concrete
• Naturally decay-resistant lumber
• Pressure-treated plywood
• Engineered wood or laminate
flooring
• Oriented-strand board (OSB)
Finish Flooring
Materials
• Clay tile
• Ceramic or porcelain tile
• Terrazzo tile
• Vinyl tile or sheets
• Engineered wood or laminate
flooring
• Carpeting
• Wood flooring
Structural Wall and Ceiling Materials • Brick face, concrete, or concrete
block
• Cement board / fiber-cement board
• Pressure-treated plywood
• Solid, standard structural lumber
(2x4)
• Non-paper-faced gypsum board
• Fiberglass insulation
• Paper-faced gypsum board
• OSB
Finish Wall and Ceiling Materials • Glass blocks
• Metal cabinets or doors
• Latex paint
• Wood cabinets and doors
• Non-latex paint
• Particleboard cabinets and doors
• Wallpaper
7.1.8 Protecting Service Equipment
When you wet floodproof a home, you should also protect the service equipment below the anticipated flood
level, both inside and outside the home in accordance with NFIP requirements. Service equipment includes utility
lines, heating ventilation and air conditioning (HVAC) equipment, ductwork, hot water heaters, and large appli-
ances. Chapter 9 describes a variety of methods you can use to protect interior and exterior service equipment.
7.2 Dry Floodproofing
Dry floodproofing involves completely sealing the exterior of a building to prevent the entry of flood-
waters. Unlike wet floodproofing (Section 7.1), which allows water to enter the building through
wall openings, dry floodproofing seals all openings below the flood level and relies on the walls of
the building to keep water out. Even if your home is dry floodproofed, water can still seep through
small openings in the sealant system or through the gaskets of shields that are protecting openings (doors and
windows). Internal drainage systems, utilizing sump pumps, are required to remove any water that has seeped
through and to remove water collected from any necessary underdrain systems in the below-grade walls and floor
of the home.
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Because the walls are exposed to floodwaters and the pressures
they exert, dry floodproofing is practical only for homes with
walls constructed of masonry or poured concrete and only
where flood depths are low (typically no more than 2 to 3 feet).
Successful dry floodproofing involves the following:
n Sealing the exterior walls of the home
n Covering openings below the flood level
n Protecting the interior of the home from seepage
n Protecting service equipment outside the home
The following sections discuss the most important considerations
regarding dry floodproofing and describe the modifications that
must be made to a home as part of a dry floodproofing project.
Protection of service equipment is discussed in Chapter 9.
7.2.1 Considerations
Flood Depth
The primary consideration in dry floodproofing, and the one
that imposes the greatest limitations on the application of this
method, is the effect of hydrostatic pressure. Because dry flood-
proofing prevents water from entering the home, the external
hydrostatic pressure exerted by floodwaters is not countered by
an equal force from water inside the home (see Chapter 2).
This external pressure results in two significant problems: heavy
unequalized loads on the walls of the home and buoyancy, or
uplift force, which acts on the entire home.
When water rises against a wall, it pushes laterally against the
wall. As the depth of water increases, so does this force, as indi-
cated by the arrows in Figure 7-4. Tests performed by the USACE2
indicated that, on a test subject, the maximum allowable flood
depth for masonry and masonry veneer walls was approximate-
ly 3 feet. In these tests, walls exposed to greater depths of water
either collapsed or suffered serious structural damage. These
tests only addressed flood loads on the house and did not ex-
pose the house to wind loads. Additionally, the tests represented
one flood event and the test procedures did not address the im-
pact of similar flood loads on the longevity of the house or its ability to resist future flood events. Masonry veneer
is not allowed by design standards to be considered as a material to resist lateral loads, such as flood loads. Houses
should not be considered resistant to increased or high loads (such as lateral loads from floodwaters) because of
the presence of a masonry veneer alone.
2 The test results are documented in the following reports published by the USACE National Flood Proofing Committee: Flood
Proofing Tests – Tests of Materials and Systems for Flood Proofing Structures, August 1988; Systems and Materials to Prevent
Floodwaters from Entering Buildings, May 1985; Structural Integrity of Brick-Veneer Buildings, 1978; Tests of Brick-Veneer Walls
and Closures for Resistance to Floodwaters, May 1978.
WARNING
Dry floodproofing cannot be used
to bring a Substantially Improved or
Substantially Damaged home into
compliance with the requirements
of your community’s floodplain man-
agement ordinance or regulation. In
addition, dry floodproofing measures
can fail during larger flood events.
WARNING
The flood depth limits discussed
here are provided as general guide-
lines only. Before you attempt to dry
floodproof your home, a design profes-
sional, such as a structural engineer,
must inspect it to determine whether
it is structurally sound and able to re-
sist increased flood loads expected as
a result of dry floodproofing. Design
professionals familiar with dry flood-
proofing techniques and technologies
should design the dry floodproofing
system so that the building’s load ca-
pacities can be properly addressed.
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FLOODPROOFING 7
Hydrostatic pressure is exerted not only by floodwater, but also
by soils saturated by floodwaters. As a result, basement walls can
be subjected to pressures much greater than that from 3 feet of
water alone (Figure 7-4). These pressures can easily cause base-
ment walls to buckle inward or collapse (Figure 2-8). For this
reason, dry floodproofing in basements is strongly discouraged. In fact, your com-
munity’s floodplain management ordinance or regulation does not allow basements
in Substantially Improved or Substantially Damaged homes to be dry floodproofed.
As shown in Figure 7-4, water and saturated soils also push up
from below the home. The buoyancy force resulting from flood
depths of over 3 feet can separate a dry floodproofed home
from its foundation and buckle concrete slab floors in dry flood-
proofed slab-on-grade homes.
The degree of danger posed by buoyancy depends on the flood depth, the type of soil at the home site, how satu-
rated the soil is, the duration of the flood, whether the home has a drainage collection and disposal system, and
how well that system works. Only an experienced engineer can evaluate these factors.
CROSS REFERENCE
For additional information about dry
floodproofing techniques, refer to NFIP
Technical Bulletin 3, Non-Residential
Floodproofing – Requirements and
Certification (1993), and FEMA
P-259, Principles and Practices for
Retrofitting Flood-Prone Residential
Structures (2012).
Figure 7-4. The lateral and
buoyancy force resulting
from the same depth of
flooding is much less on a
home without a basement
(a) than on a home with a
basement (b). The pressure
on basement walls is caused
by water and saturated soils.
Flow Velocity, Erosion and Scour, Debris Impact, and Wave Action
Dry floodproofing does not protect a home from the hydrodynamic force of flowing water, erosion and scour,
the impact of ice and other floodborne debris, or wave action. If your home is located in an area subject to any
of these hazards, consider an alternative retrofitting method, such as elevation on an open foundation (Section
5.2.3) or relocation (Section 6.1). Dry floodproofing a home does not change its vulnerability to damage from
high winds or earthquakes.
Flood Duration
Flood duration is an important consideration because the potential for seepage through and deterioration of the
materials used to seal the home increase with the length of time that the home is exposed to flooding. Also, the
longer the duration, the greater the likelihood that the soil beneath and adjacent to the home will become fully
saturated and add to the loads on the walls and floor (Figure 7-4). Additionally, most dry floodproofing methods
depend on sump pumps to address water that has leaked into the house, and those pumps require electricity to
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run. Although some sump pumps have battery backups, these backups typically only last a few hours, so a genera-
tor system may also be required for long-duration flooding. If your home is in an area where floodwaters remain
high for days, weeks, or even months at a time, consider an alternative retrofitting method, such as elevation or
relocation.
Human Intervention
Dry floodproofing systems almost always include components that have to be installed or activated each time
flooding threatens. One example is a flood shield placed across a doorway. For this reason, dry floodproofing is not
an appropriate retrofitting method in areas where there is little or no flood warning or where, for any other rea-
son, the homeowner will not be able or willing to install shields or other components before floodwaters arrive.
Post-Flood Cleanup
Remember that floodwaters are rarely clean. They usually carry sediment, debris, and even corrosive or hazardous
materials, such as solvents, oil, sewage, pesticides, fertilizers, and other chemicals. The walls of a dry floodproofed
home will be exposed to whatever is in the floodwaters. Cleaning up a dry floodproofed home after a flood may,
therefore, involve not only removing mud and debris from around the home, but also decontaminating or dis-
infecting walls and other exterior surfaces. Hurricane Sandy Fact Sheet 1, Cleaning Flooded Buildings (FEMA.
2013a), provides some guidance on cleaning up following a flood.
7.2.2 Modifications Required for Dry Floodproofing
Dry floodproofing involves the use of sealants and shields, the installation of a drainage system, and the protec-
tion of service equipment.
Sealants
Except for some types of high-quality concrete, most wall materials are not impervious to water. Therefore,
sealants must be applied to the walls of a dry floodproofed home to prevent leakage. Prior to applying a sealant, a
structural engineer must determine whether the walls can resist the loads. Flexible sealants are compounds (such
as asphalt coatings) or materials (such as polyethylene film) that are applied directly to the outside surface of the
home walls. Sealants must also be applied to all structural joints, such as the joint between the walls and a slab
floor, and to any other openings below the flood level, such as those where utility lines enter the home through
the walls or floor. Some of these sealants are designed to be applied to the outside of the wall, while others can be
applied to the inside of the walls. Which sealant is appropriate will depend on the manufacturer’s recommenda-
tions and the access to the wall surfaces or structural joints.
Sealants that can be applied to outside walls include cement- and asphalt-based coatings and clear coatings, such as
epoxies and polyurethanes. Cement- and asphalt-based coatings are often the most effective, but they can change
the appearance of the wall (Figure 7-5). The aesthetic advantage of many exterior treatments is lost when these
coatings are applied over them. Clear coatings do not change the appearance of the wall, but are less effective
Figure 7-6 shows one method of sealing masonry walls with an asphalt-based coating that does not detract from
their appearance. In this method, a new masonry veneer is added to the existing veneer after the coating is applied.
An alternative to using coatings is to temporarily wrap the entire lower part of the home in polyethylene film
when flood conditions threaten. This alternative is sometimes referred to as the “wrapped home” technique. The
cross-section view in Figure 7-7 shows how this technique works. There must be at least several hours of warn-
ing time in order to properly deploy this method. The use of a flood wrapping system should be considered
temporary and largely an emergency solution to a flooding problem.
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FLOODPROOFING 7
Figure 7-5. Example of an exterior application of a spray-applied asphalt membrane (left – courtesy of GMX, inc.) and an
interior application of a fiber reinforced polymer wrap (right).
Figure 7-6. A way to seal an
existing brick-faced wall is
to add an additional layer of
brick with a seal in between.
Please note that weep holes
(drainage) and wick drains
are moved up to prevent
moisture from getting inside
the walls.
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Polyethylene film is not a strong material; it cannot withstand water pressure on its own and can be punctured
fairly easily. As a result, the following requirements must be met when the wrapped home technique is used:
n The manufacturer’s literature must demonstrate applicability of the film to the home’s building materials.
Rely on actual test results, if available.
n The installation must be carried out very carefully. Even a small hole in the film will leak under the
pressure of floodwaters.
n The film must be applied directly against the walls of the home so that the walls, rather than the film,
provide the resistance to water pressures. This may require strengthening the walls of the home and
openings, such as doors.
n Where the film covers doorways and other openings, it must be backed by framed plywood panels that
are braced to resist water pressures.
n A temporary drainage system must be provided to collect and dispose of any water that leaks through
holes in the film. (Drainage systems are discussed later in this section.)
n The duration of flooding should be less than 12 hours and the flood depth adjacent to the home should
not exceed 1 foot.
Home wrap systems require secure connections at both the top and bottom of the wrap. The actual loads imposed
vertically on the wrap are difficult to determine because they can vary depending on the quality of the installation.
Voids or weak spots left from poor construction may force the wrap to carry the weight of the water and should
be avoided.
Figure 7-7. In the “wrapped
home” method, the lower
portion of the home is
protected with a temporary
layer of polyethylene film. As
shown, a temporary drainage
line is also required.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 7-15
FLOODPROOFING 7
The following should be considered in the selection of a top-of-
wall connection system:
n A clamping system that uniformly supports the wrap.
A small spacing on the connections and a connection
system with some rigidity on the outside of the wrap
can provide this needed support.
n The existing wall construction can vary widely. Part of
the connection may need to be a permanent part of the
wall.
Anchoring a wrap into the ground at the base of a wall is the most important link in the wrap system (see Figure
7-7). The following recommendations should be followed during selection of a system:
n A drain line between the wrap and the building is usually required to remove any water that leaks
through the wrap or seeps through the soil under the anchor.
n As with the top-of-wall connection, wrap forces are difficult to determine. Details that have worked in
the past and that are compatible with the building and the selected wrapping system should be followed.
n The end of the wrap should be buried at least below the topsoil layer. Additional ballast may be needed
(e.g., sandbags, stone) to prevent wrap movement in a saturated and/or frozen soil condition.
n The product literature for the wrap material and applicable codes and standards should be reviewed and
followed.
Before selecting a wrapping system, make sure that the manufacturer’s literature addresses the following issues.
n Are any chemicals used or stored around the home or onsite that could damage the wrapping system?
Evaluate adjacent properties to identify any potential chemicals that could damage a wrap system.
n How should the wrapping system be repaired and approximately how much additional wrapping
material is required for each repair? Understanding whether the wrapping material can be repaired
under flood conditions or if it must be dry for a proper repair to be made is important.
Shields
Shields are flood barriers placed over openings in walls such as doorways and windows. Shields can be made of
several materials, depending on the size of the opening to be covered, and should include gaskets along their
edges. When flood depths are expected to reach the maximum allowable 2 to 3 feet, shields for openings wider
than approximately 3 feet must be made of strong materials such as heavy-gauge aluminum or steel plates (Fig-
ure 7-8); shields for lesser depths and smaller openings can be made of lighter materials. Because of the potential
risk of a shield failing, a structural engineer must assist with the design of the shields and evaluate the entire dry
floodproofing system. The engineer may also determine that the walls to which the shield is attached need to be
strengthened to carry the flood loads associated with the shield.
Because permanently blocking all doors and other openings would be impractical, shields are usually placed tem-
porarily, after flood warnings are issued. Most residential shields are light enough that they can be stored in the
home and, when needed, brought out and bolted in place or secured in permanently installed brackets or tracks
(Figure 7-9). Although rare for residential applications, some larger, heavier shields may have to be permanently
installed on hinges or rollers so that they can be opened and closed easily.
WARNING
Wrap systems may be affected by
freeze-thaw cycles. Careful installa-
tion in accordance with manufacturer
instructions and evaluation of perfor-
mance in frozen climates is advisable.
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7 FLOODPROOFING
Figure 7-8. Heavy-gauge
metal shield over sliding
glass door opening.
Figure 7-9. Light-gauge
metal shield held in place by
permanently installed tracks.
Companies that specialize in flood protection devices can provide custom-fitted flood shields. Usually, these com-
mercial shields are made of heavy-duty materials, and some are equipped with inflatable or other types of gaskets
that help eliminate leaks. Gaskets left exposed to the elements can rapidly decay. Gasket materials should be stored
indoors and checked periodically for tears or decay. A faulty gasket can allow floodwaters to get past the gasket,
nullifying any of the other floodproofing techniques.
An alternative to using shields is to permanently seal openings. For example, a low-level window can be removed
or raised and the opening bricked up or filled with glass block (Figure 7-10).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 7-17
FLOODPROOFING 7
Figure 7-10. Low window
raised approximately 2 feet
and original opening filled
with brick.
DEFINITION
Underseepage is water that migrates
downward along the sealed walls of a
home and then under the foundation.
Drainage Systems
Sealants and shields provide the bulk of the protection in dry
floodproofing, but they may permit some leakage, especially
during floods of longer duration and when damaged by debris.
They also do not protect against “underseepage,” water that
migrates downward along the sealed wall and then under the
foundation. For these reasons, a dry floodproofed home must
have a drainage system that will remove any water that enters
the home through leaks in sealants and shields and any water
that accumulates at the base of the foundation. Depending on
the permeability of the soils around and under the home, the
drainage system may also have to be designed to reduce buoy-
ancy forces.
An adequate drainage system includes drains along the base of the foundation and under the floor. The drains
consist of perforated pipe surrounded by crushed stone. The pipes collect water that seeps through the ground
and channel it to a central collection point equipped with a sump pump. This system is shown in Figure 7-11.
The sump pump must have sufficient capacity to handle the inflow of water and must have an emergency power
source, such as a portable generator, so that it will continue to operate if conventional electric service is disrupted.
Depending on soil conditions, seepage rates may exceed the maximum discharge rates of standard sump pumps.
Drainage systems should be designed and laid out based upon several factors, such as the design flood depth, soil
conditions, and the construction methods and materials of the area to be protected. These factors will also affect
the size of the sump pump and the requirements for a backup power source. Because of the complexity of these
designs and the potential consequences of a system failure, seek the input of a design professional familiar with
dry floodproofing systems.
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Figure 7-11. Drainage system
for a dry floodproofed home.
Protecting Service Equipment
Dry floodproofing a home will not protect service equipment outside the home. Examples of service equipment
typically found outside the home are utility lines, air conditioning compressors, heat pumps, and fuel storage
tanks. Chapter 9 discusses the protection of service equipment.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 8-1
8.0 Barriers
Levees and floodwalls are types of flood protection
barriers. A levee is typically a compacted earthen
structure; a floodwall is an engineered structure usu-
ally built of concrete, masonry, or a combination
of both (Figure 8-1). Barriers can be built to protect a single
structure or multiple structures. Types of barriers include levees,
floodwalls, and temporary barriers.
Table 8-1 includes a summary of advantages and disadvantages
for using barriers as a mitigation measure.
WARNING
Floodwalls and levees are not per-
mitted to address Substantial
Improvement/Damage and do not
bring new buildings into compliance
with NFIP regulations unless they are
accredited per 44 CFR § 65.10.
Furthermore, the floodwalls and
levees described in this chapter will
not lower your flood insurance premi-
um cost.
Figure 8-1. Structure
protected by levee (on left)
and floodwall (on right).
NOTE
For more information about barriers refer to FEMA 511, Reducing Damage from Localized Flooding.
USACE’s Floodproofing – How to Evaluate your Options (FEMA.2005) document is also a good source for
barrier options.
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8 BARRIERS
Table 8-1. Considerations for Using Barriers
Advantages Disadvantages
• Floodwaters cannot reach the structure(s) in the protect-
ed area and, therefore, will not cause damage through
inundation, hydrodynamic pressure, erosion, scour, or
debris impact.
• The structure and the area around it will be protected
from inundation, and no significant changes to the struc-
ture will be required.
• Barriers may not be used to bring a Substantially
Damaged or Substantially Improved structure into com-
pliance with the community’s floodplain management
ordinance or regulation.
• Cost may be prohibitive, as a large area may be required
for construction.
• Periodic maintenance is required.
• Local drainage can be affected, possibly creating or
worsening flood problems for others.
8.1 Levees
Levees are embankments or structures constructed of compacted
earthen materials. Construction of a levee begins with excavat-
ing and inspecting the cutoff trench. This gives the designer a
better look at the subsurface soil conditions, so that the presence
of roots, utility lines, and animal burrows, or changes in soil
conditions can be considered during the design process. The in-
terior of the levee is composed of an impermeable core, usually
clay. The lifts of impervious clay fill are placed in 6-inch layers,
with each lift compacted to the density specified by the designer
(Figure 8-2). As with large floodwalls, a licensed Professional
Engineer should perform the levee design and certification.
DEFINITION
A cutoff trench is a core located
below the base of a dam or levee
structure. The trench is filled with an
impervious material, such as clay, to
form a watertight barrier to prevent
under-levee seepage.
Figure 8-2. Levee
construction.
Levees can be used to completely circle a building. However, they require a lot of space and a large quantity of
earthen fill. Unless the fill is readily available nearby, hauling it to the site may prove to be cost-prohibitive. Inte-
grating parts of the new levee into existing ground that is close to or above the levee’s design elevation can help
reduce construction costs.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 8-3
BARRIERS 8
8.2 Floodwalls
A floodwall is an engineered structure made of reinforced concrete or reinforced concrete block. A typical residen-
tial floodwall usually varies from 1 foot to 4 feet in height and can surround a structure or, depending on flood
depths, site topography, and design preferences, protect building openings, such as doors, windows, and base-
ment entrances, including entry doors and garage doors. When built with decorative bricks or blocks or as part
of garden areas, floodwalls can be attractive architectural or landscaping features. They can also be built solely for
utility, usually at a much lower cost.
Because a floodwall is made of concrete or masonry rather than compacted earth, it is more resistant to erosion
than a levee and requires less space than a levee that provides the same level of protection. However, floodwalls
are often more expensive. As a result, floodwalls are normally considered only for sites where there is not enough
space for a levee or where high-velocity flows may erode a levee. Also, some property owners prefer floodwalls
because they can be more aesthetically pleasing and allow for the preservation of existing site features, such as
landscaping and trees, or covered with a decorative stone finish (Figure 8-3).
Figure 8-3. Structure
protected by a floodwall with
decorative stone finish.
8.3 Temporary Barriers
Several types of temporary barriers are available to address typical flooding problems. They work with the same
principles as permanent barriers, such as floodwalls or levees, but can be removed, stored, and reused in subse-
quent flood events. Most of these barriers are meant to take the place of sandbag floodwalls and may also be used
to reinforce existing permanent barriers such as levees (Figure 8-4).
Temporary barrier products are designed so that they can be used numerous times. The Association of State Flood-
plain Managers (ASFPM) worked with the USACE and Underwriters Laboratories (UL) to establish a testing/
certification program for temporary flood barriers. ASFPM, UL, and USACE initiated program development, and
FM Approvals (a division of FM Global) developed an approval system for recognizing temporary barriers as flood
8-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
8 BARRIERS
abatement equipment for their policyholders. In 2006, FM Approvals published FM Standard 2510, Approval Stan-
dard for Flood Abatement Equipment (2006). The current FM Approvals test protocols are for self-supporting, temporary
barriers designed to protect against riverine flood depths up to 3 feet. These barriers are not tested for coastal
flooding applications, where the presence of saltwater may hinder their performance. Because saltwater is denser
than freshwater, a barrier filled with freshwater in a coastal location may float instead of providing protection
against flooding.
Figure 8-4. Two-foot-high
water-filled temporary barrier
protecting a residence from
flooding ( 2010 – Courtesy of
Hydrological Solutions, Inc.).
8.4 Technical Considerations
The factors discussed in the following sections affect the type of a barrier best suited for your home and should
be considered before making a barrier selection.
8.4.1 Height of Barrier
When barriers are built to protect a single structure, they are referred to as “residential,” “individual,” “on-site,”
or “local” levees and floodwalls. Levees and floodwalls should be built to protect the residence from predicted
flood heights as depicted on FEMA FIRMs, in FISs, or local flood vulnerability analyses. If the height of the levee
or floodwall would make the project cost-prohibitive, then elevation or relocation of the residence should be con-
sidered. The practical, cost-effective heights of these levees and floodwalls are usually limited to 6 feet and 4 feet,
respectively. These limits are the result of the following considerations:
n The higher the levee or floodwall, the greater the depth of water that builds behind it and the greater the
water pressure exerted on the barrier. Taller levees and floodwalls must be designed and constructed to
withstand the increased pressures. Meeting this need for additional strength greatly increases the cost of
the levee or floodwall, usually beyond what an individual property owner can afford.
n Because taller levees and floodwalls must be stronger, they must also be more massive, so they usually
require more space than is likely to be available on an individual lot. This is especially true of levees.
n Local zoning and building codes may also restrict the use, size, and location.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 8-5
BARRIERS 8
Local floodplain management ordinances and regulations may require a “no-rise” study to prove that the barrier
system will not increase flood heights downstream of the barrier structure.
If the flood depth at the project site is above the practical height limits of available barriers, an alternative miti-
gation method, such as elevation, should be considered. The levee or floodwall can always be overtopped by a
higher-than-expected flood regardless of the height of the barrier. Overtopping is a greater concern for a levee
than a floodwall because a small amount of overtopping can cause erosion at the top of the levee and cause it to
fail.
8.4.2 Basement Foundations
Special design considerations are necessary when levees or floodwalls are built to protect a structure with a base-
ment. Even though the surface water is kept from coming into contact with the structure, the soil below the levee
or floodwall and around the structure can become saturated, especially during floods of long duration. The re-
sulting pressure on basement walls and floors can cause them to crack, buckle, or even collapse. An analysis by a
qualified soils engineer can help to determine a sufficient distance for the floodwall or barrier from the structure
to lessen or alleviate this pressure.
8.4.3 Soil Conditions
The type of soils encountered may have a significant impact on the choice of barriers as a flood protection option.
This is true regardless of the choice of a permanent barrier or a temporary barrier. The following soil character-
istics must be considered:
n Bearing capacity. This is the capacity of a soil to support applied loads. Permanent barriers such as
levees and floodwalls, as well as many temporary barriers, are very heavy. If the soil type has low bearing
capacity, the barrier may either fail structurally or begin to sink, losing its design protection height and
capability. In this instance, alternative mitigation, such as elevation, relocation, or floodproofing should
be considered.
n Permeability. Barriers should be deployed on tight, impermeable soils. If the soils are permeable, such
as sand or sandy loam, steps need to be taken to counteract the seepage of water under or through the
barriers. These steps include installing an impervious core for a levee and a cutoff trench filled with
impermeable bentonite clay soil. Bentonite clay should also line the levee surface. A cutoff trench is a
below-grade core of bentonite clay that prevents movement of pervious materials, such as loose sand and
gravel, which can compromise the levee’s performance.
8.4.4 Duration of Flooding
All barriers exposed to floodwaters for an extended period of time will be subject to seepage or leakage. If the du-
ration of flooding is relatively short (less than 1 day) and the depth of flooding is relatively low (less than 1 foot),
many barriers will at least slow down the effects of inundation. Longer exposures require barriers that are better
engineered and more carefully constructed or deployed. Likewise, deeper flood depths also need to be considered
as a result of the extremely high forces exerted on the barriers by the weight of the floodwaters.
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8.5 Additional Considerations
The factors discussed in the following sections involve practical considerations affecting barrier selection.
8.5.1 Annual Maintenance
A barrier requires periodic inspections and maintenance to address any necessary repairs. Otherwise, small prob-
lems, such as cracks, loss of surface vegetation, erosion and scour, animal tunnels, and trees and shrubs can quickly
become large problems during a flood event. The barrier should be inspected at a minimum each spring and fall,
before each impending flood, and after each flood event. To facilitate slope stability as well as maintenance and
safe grass mowing, the side slopes of most levees should not be steeper than 1 foot vertically to 2.5 feet horizon-
tally (1:2.5) on the floodwater side and 1 foot vertically to 3 feet horizontally (1:3) on the land side. In general,
driveways positioned to provide access over a protective levee that circles a residence should not be steeper than
1:3. Trees and large shrubs should not be located on barriers as they can be overturned during high-wind events
and compromise the structural integrity of the levee. When trees and shrubs die, their roots decay, leaving cavities
for water to pass through, which can cause the barrier to fail.
Homeowners interested in additional information on inspection of levees can refer to the following technical
manuals available for download from the FEMA Website at http://www.fema.gov/technical-manuals-and-guides:
Technical Manual for Dam Owners: Impacts of Animals on Earthen Dams (FEMA 473) and Technical Manual for Dam Owners: Impact
of Plants on Earthen Dams (FEMA 534). Although these manuals were developed for dam owners, they contain many
principles that are applicable to levees.
8.5.2 Housing of Occupants
Although a residence can be used during construction of a barrier, the residence should not be occupied during
a flood event. Levees and floodwalls may give the homeowner a false sense of security. Every flood is different and
one that exceeds the height of the barrier could occur at any time. If water overtops the barrier, the protected area
will fill rapidly. Homeowners should evacuate when a flood warning is first issued.
8.5.3 Access to Structure
Barriers can make access to the structure difficult. Openings must be created or provided for driveways, side-
walks, and other entrances. These openings must be closed prior to the flood event, as floodwaters can rise rapidly
enough to prevent an opening from being closed. Examples of these closure mechanisms for floodwalls include
shields similar to the ones used in dry floodproofing or prefabricated panels and permanently mounted, hinged,
or sliding flood gates and prefabricated stop logs or panels for levee openings. Unless the gates remain in the
closed position at all times, human intervention is required to close an entry point to prevent rising floodwaters
from entering the structure (Figure 8-5).
8.5.4 Human Intervention
As described in Section 8.5.3, openings in the barrier must be closed prior to a flood event. Putting the closure
mechanisms in place requires human intervention. The barrier will not protect the structure from flooding unless
the property owner is willing and able to operate all closures before the flooding begins.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 8-7
BARRIERS 8
Figure 8-5. The City of
Boulder, CO, installed a “pop
up” closure to this floodwall
at a City office building
subject to flash floods. The
closure floats up into place
automatically when the site
is flooded.
8.5.5 Interior Drainage
A barrier that keeps floodwater out of the protected area also will keep water in. Drains and sump pumps should
be installed to remove water collected inside the barrier. In addition, caution must be taken to ensure that local
drainage patterns in the area are not disrupted. An interior drainage system, including a sump pump (Figure 8-6),
must be installed in an area protected by a levee or floodwall.
Figure 8-6. Small patio
floodwall with sump pump.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-1
9.0 Protecting Service
Equipment
Homes are typically provided with a variety of building support service equipment. Five major services
make up the mechanical, electrical, and plumbing (MEP) systems found in most homes:
n HVAC systems, including air conditioning
compressors, heat pumps, furnaces, ductwork, and
n Fuel systems, including natural gas lines and fuel
storage tanks
n Electrical systems, including wiring, switches,
outlets, fixtures, and fuse and circuit breaker panels
n Sewage management systems, including sewer lines,
drains, septic tanks, and drainage fields
n Potable water systems, including water lines, private
wells, storage tanks, and water heaters
Most homes also have communications systems, including
telephone, internet, and cable television lines.
Some MEP equipment is typically located inside a home (e.g., furnaces, ductwork, water heaters, appliances) and
some is located outside (e.g., propane tanks, air conditioning and heat pump condensers, septic tanks). Other MEP
equipment includes components found both inside and outside a home (e.g., electrical systems; plumbing, gas,
telephone, internet, and cable television lines; oil storage tanks).
The original placement of service equipment in and around your home was probably based on standard construc-
tion practices and the builder’s preferences. As a result, service equipment is often installed in areas where it will
be exposed to floodwaters, such as in a basements or crawlspaces or at ground level outside the home.
Elevation, wet floodproofing, and dry floodproofing protect the structure of your home from damage by floodwa-
ters. But these methods, unlike relocation and the construction of levees or floodwalls, do not prevent floodwaters
CROSS REFERENCE
For more information about elevating
electrical and HVAC systems, refer
to FEMA 348, Protecting Building
Utilities from Flood Damage (1999),
Hurricane Sandy Recovery Advisory
No. 3, Restoring Mechanical,
Electrical, and Plumbing Systems
(2013), and FEMA 499, Fact Sheet
No. 8.3: Protecting Utilities (2010).
9-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
9 PROTECTING SERVICE EQUIPMENT
from reaching the home. For this reason, protecting service equipment located below the expected flood level is
an essential part of a retrofitting project.
When relocating or elevating MEP systems, consider horizontal and vertical clearances; venting; and unions,
fittings, and valves. The replacement of MEP systems also presents an opportunity to improve the energy efficiency
of your house by selecting high-efficiency equipment that may not have been available when the damaged equip-
ment was installed.
If your house has been damaged by a flood, the repair and restoration work must not violate any floodplain
management requirements in effect when the house was originally built. Always check with your local building
department, as locally enforced codes may differ from what is described in this chapter. For example, some com-
munities may require all MEP system restoration or alteration work to comply with the applicable sections of the
current code, even in houses that are not Substantially Damaged. When considering relocating or elevating MEP
systems, follow all applicable codes, regulations, and manufacturers’ installation requirements.
Flood Insurance Implications
Houses built after communities joined the NFIP were required to be elevated to or above the BFE to minimize
flood damage. These houses should already have elevated MEP systems and components. However, if some equip-
ment was not elevated (such as a furnace or ductwork located in a crawlspace), owners may be paying much
higher NFIP flood insurance premiums than necessary. Replacing damaged equipment and elevating it on plat-
forms not only minimizes future damage, but may lower flood insurance premiums. Check with insurance agents
to find out whether taking this action will affect your flood insurance premiums.
You can protect interior and exterior service equipment in three ways: elevating it, relocating it, or protecting it
in place. More information on these methods can be found in FEMA 348, Protecting Building Utilities from Flood Damage
(1999).
9.1 Elevation
Service equipment installed outside your home can usually be
elevated above the flood level. Equipment mounted on an exte-
rior wall (e.g., an electric meter, incoming electric, telephone,
and cable television lines) usually can be mounted higher up on
the same wall. Equipment typically placed on the ground (e.g.,
air conditioning compressors, heat pumps) can be raised above
the flood elevation on pedestals or platforms (Figures 9-1 and
9-2).
When you elevate service equipment, you should always con-
sider raising it at least 1 foot above the BFE, just as when you
protect your home with one of the methods described in this
guide. Elevating service equipment an additional 1 or 2 feet
often will not increase your retrofitting costs significantly but
will provide an extra measure of flood protection. Since gas and
electric meters are typically owned by a utility company, you
may not be allowed to move or elevate them without the utility
company’s permission.
NOTE
Some utility companies have re-
quirements for ensuring their meter
readers can access the meters, such
as providing stairs to a platform under
the reader. Check with your service
provider before elevating service
equipment. Refer to the Hurricane
Isaac Recovery Advisory No. 2,
Minimizing Damage to Electrical
Service Components (2012).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-3
PROTECTING SERVICE EQUIPMENT 9
Figure 9-1. Air conditioning / heat pump
compressor mounted on a brick pedestal
outside an elevated home.
Figure 9-2. Air conditioning/
heat pump compressor
mounted on a cantilevered
platform attached to a
home elevated on an open
foundation. (Source: FEMA
P-55 Figure 12-2)
9-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
9 PROTECTING SERVICE EQUIPMENT
The feasibility of elevating equipment inside a basement or
garage depends largely on the flood level. Simply raising the
equipment above the floor using a solid pad (such as masonry
or concrete) or a framed platform (wood or steel) may be possi-
ble. Outdoor equipment can be elevated on a platform attached
to the side of the house. The materials selected to construct el-
evated platforms should meet the requirements described in
NFIP Technical Bulletin 2, Resistant Materials Requirements (2008),
and should be non-combustible when required by the code. A
pad should be properly anchored to the floor system or slab, and
the equipment should be properly anchored to the pad.
As the height of the flood level increases above the floor, the amount of space available above the flood level dimin-
ishes and elevation is feasible only for smaller pieces of equipment (e.g., electrical system components, ventilation
ductwork, or specialized equipment such as furnaces designed to be suspended from the ceiling). If the flood
level is at or near the ceiling, elevation may not be possible. Instead, equipment must be relocated or protected in
place as described in Section 9.3.
Keep in mind that most service equipment must remain accessible for routine maintenance. For example, your
fuel company must be able to reach your fuel tank to fill or empty it. Before elevating any service equipment,
check with the utility company to find out whether it has any requirements that would prohibit elevation or
restrict elevation height.
Also, remember that any large equipment elevated on platforms or pedestals, both inside and outside your home,
may be more vulnerable to wind and earthquake damage and may require additional bracing or anchorage. A
design professional must determine the expected wind and earth¬quake forces at the site and account for them
in the elevated platform design.
This precaution is especially important for elevated fuel storage tanks, which could rupture if they are dislodged
or toppled by wind and earthquake forces. In earthquake-prone areas, fuel storage tanks are sometimes equipped
with cutoff valves that can help prevent leaks when supply lines are ruptured. Your utility service provider can
give you more information about cutoff valves and other ways to protect fuel storage tanks from natural hazards.
9.1.1 Maintaining Horizontal and Vertical Clearances
When moving equipment, either to another floor or elevated on a platform, maintain the recommended horizontal
and vertical clearance around it as required by building codes and the National Electrical Code or as recommended
by manufacturers. Minimum clearances required for equipment, conduits, piping, and duct work should be con-
sidered before relocating or elevating equipment. Designing for the minimum clearance is important to maintain
air circulation, meet insurance or code requirements related to distance from combustible building materials, and
provide space for maintenance. Most codes dictate that clearance requirements should follow those specified on
the equipment label or installation instructions. Required clearance typically ranges from 6 to 36 inches, and can
sometimes be reduced by installing heat shields if allowed by the building code. The use of a heat shield or other
method to reduce clearance should be verified in codes and manufacturers’ installation requirements. Failure to
maintain proper clearance can result in safety issues, including fire, and can void equipment warranties.
NOTE
When elevating HVAC and other
equipment, be sure to leave sufficient
space around the unit to allow access
for maintenance work.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-5
PROTECTING SERVICE EQUIPMENT 9
9.1.2 Venting Considerations
Oil- or gas-fueled boilers, furnaces, and water heaters require adequate combustion air and venting of exhaust
gases. Although some units may vent exhaust directly out of the unit through an exterior wall, other units may
need to vent exhaust through a chimney. The type of venting system and the clearances necessary for the venting
system may affect how high the equipment can be elevated.
The venting system should be tested to ensure it draws adequate air and backdrafting does not occur. If relocating
equipment, consider the required venting system, as it may affect the final placement of the unit.
9.1.3 Unions, Fittings, and Valves
When relocating or elevating equipment is not feasible, consider replacing unions, fittings, or valves to allow
faster replacement of equipment when damaged, or disconnecting equipment prior to a flood event and relocat-
ing it to a higher floor. Although this approach will not bring a non-conforming building into compliance with
NFIP requirements, it may reduce potential flood damage to utility systems.
9.2 Relocation
When space permits, you can move service equipment from a
basement or other area below the flood level to an upper floor
of the home or even an attic. Relocation usually requires more
extensive changes to both your home and the equipment being
moved, but it often provides a greater level of flood protection
because the relocated equipment is farther above the flood lev-
el. In some situations, you may also be able to relocate outside
equipment to higher ground, but only when the slope of your
lot and other site conditions permit.
Another relocation option is to build a new, elevated utility room as an addition to your home. The addition could
be built on an open foundation or extended foundation walls.
Relocating and elevating equipment and systems can be a simple process, such as elevating a water heater on a
small platform, or a complex process involving relocating equipment to a higher floor or to a new addition built
specifically as a utility room. Each type of system has specific vulnerabilities, characteristics, and restrictions on
placement that can affect a homeowner’s ability to relocate it.
9.2.1 Electrical Panels
Power outages after a flood event often last much longer if a house’s electrical panel is located below the flood
elevation because the panel must be replaced before power can be restored. To address this problem, the electrical
panel should be relocated to an elevation above the lowest floor (into the living space). When moving electrical
panels to an elevation above the lowest floor, additional components, such as a service disconnect, may need to
be incorporated into the system to meet the requirements of the National Electrical Code. Also, when relocating
electrical panels, codes or local requirements may require replacing significant portions of the house wiring. For
additional information on relocating electrical systems, consult Hurricane Isaac Recovery Advisory No. 2, Minimiz-
ing Damage to Electrical Service Components (2012).
CROSS REFERENCE
Chapters 3 and 4 of FEMA 348,
Protecting Building Utilities from
Flood Damage (1999), discuss relo-
cation of service equipment in detail.
9-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
9 PROTECTING SERVICE EQUIPMENT
9.2.2 Electric Meters
Damage to electrical meters is common during flood events. Relocating meters can often result in reduced out-
age times following flood events. Although some electric utility companies allow meters to be relocated, they
often have specific requirements and specifications. Most electric utility companies do not want their employees
to be put at risk climbing ladders or stairs. You may be able to work with your electric utility company to find an
appropriate spot to relocate your meter to reduce the risk of it being damaged by floodwaters.
9.2.3 Electrical Wiring
In many houses, some wiring is located below the BFE, especially where the utility service is routed underground.
If wiring is located below the BFE and the wiring is not rated for wet locations, the wiring should be encased in
a non-corrosive metal or plastic pipe (conduit) when allowed by code. The conduits should be installed vertically
to promote thorough drainage when floodwaters recede. Damaged wiring is easier to replace if it is installed in
a conduit.
9.2.4 Mechanical Systems
Mechanical systems include the HVAC system, duct work, and the air handler that delivers the conditioned
air throughout the house. Elements of the heating and cooling system below the BFE are subject to flooding.
Ductwork beneath a house’s floor system is susceptible to flooding and should be removed and replaced if it is
inundated by floodwaters. The ductwork connected to the furnace and air handler is often the most prone to flood
damage because the furnace is often located in the basement or the building’s lowest floor.
In many instances, elevating mechanical systems above the BFE may not be possible. They should still be elevated
as high as possible. Relocating mechanical equipment may require replacing ductwork and moving electrical sup-
plies and refrigerant lines. Physical obstructions, such as walls or framing, may restrict the relocation of ductwork
and the final location of the system components.
Condensing units. Protecting the condensing unit for an air conditioning system can often be achieved by elevat-
ing it on a platform or attaching a platform to the side of the house. A cantilevered platform is preferred over a
platform on posts. Posts can obstruct floodborne debris and are more vulnerable to damage and failure, including
floodborne debris impacts and undermining by scour and erosion.
Heating systems. Boiler systems, which are typically oil- or gas-fired, heat water and either force hot water or
steam through radiators or baseboards throughout the home. A hot water boiler system consists of the main boil-
er, heat exchanger and burner, circulation pumps or control valves, and an expansion tank. Many components of
a boiler system can be damaged by contact with floodwaters. Protecting a boiler system from flooding usually
requires raising the system in its entirety. Although most boiler systems in residential use are hot water systems,
the protection of a steam boiler is similar. Relocating a boiler system to an upper level is ideal, but can present
some significant challenges, such as needing to reroute the plumbing associated with the system. Elevating the
boiler as high as possible on its current floor may be more practical. The main concerns when elevating a boiler are
clearances, venting the exhaust, and protecting the supply tank from contamination. Systems using heating oil rely
on either an above- or below-ground storage tank. The storage tank should be properly anchored and sufficiently
sealed to prevent floodwater from contaminating the heating oil or allowing the oil to be released.
A furnace or forced air heating system uses oil or natural gas (and sometimes electricity) to heat air blown across
heating coils in the system. Relocating these systems to upper floors or attic areas may be possible. If elevating the
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-7
PROTECTING SERVICE EQUIPMENT 9
furnace to an upper floor is not possible and elevating the furnace in its existing location below the living area
is the only practical mitigation measure, the required clearances and venting of the unit must be accommodated.
9.2.5 Water Heaters
Water heaters, which are oil- or gas-fired, are powered from an electric coil. Conventional residential water heaters
that use storage tanks typically range in capacity from 40 to 80 gallons. When exposed to floodwater, the internal
components of the water heater can be damaged.
Electric water heaters. In some buildings, electric water heaters can be relocated to a higher floor or the
attic. Relocating the unit requires plumbing and electrical work, as well as a method to drain the tank and prevent
water damage from leakage. Although relocating a water heater to the attic effectively protects it from flood dam-
age, the heater must be equipped with a drain pan and drain to avoid costly water damage in the event of leakage.
If a water heater is placed in an attic, it should be routinely maintained and inspected for leaks or other problems.
Oil or gas-fired water heaters. Oil- or gas-fired water heaters must be vented and may, therefore, be difficult to
move into a main living space. If an appropriate location for the water heater is not available on a higher floor, it
can potentially be elevated in its current location. Elevating the tank usually requires a small pad or platform, an
appropriate location to vent the exhaust, and extending or shortening water supply lines and distribution lines.
Other water heaters. Although more expensive than conventional water heater systems, tankless systems, which
heat water instantaneously, require significantly less space and may present a flood mitigation opportunity
because of their smaller size. Converting a conventional water heater unit fueled by natural gas to a tankless system
requires minimal additional work. Electric tankless water heaters, by comparison, may not be practical because
of the electrical system upgrades needed in some houses to provide the additional electrical power for the water
heater.
Although moving equipment into the attic area may appear to be an effective use of space, equipment such as
water heaters can cause problems if they are not properly installed. Drain pans and piping to address a water heater
leak must be carefully considered to make sure water will not overflow and damage rooms below. In areas subject
to freezing temperatures, drain lines could freeze and prevent water from draining, causing significant interior
water damage.
9.2.6 Washer/Dryer Units
Many washing machines and clothes dryers are located in basements, where they are vulnerable to flooding.
Relocating this equipment to a higher floor may not be practical if space is limited in the living area. Even minimal
elevation may prevent the units from being damaged in low-level flooding situations. A permanent pad or plat-
form should be constructed to elevate these units; stacked bricks or blocks should not be used because they can
shift and result in injuries to users or damage to the equipment. Elevating washing machines and clothes dryers
may require altering the water and drain piping, electrical connections, and gas connections.
9.3 Protection in Place
When elevation and relocation are infeasible or impractical, you may be able to protect service equipment in place
with low floodwalls and shields and with anchors and tie downs that prevent flotation. Plumbing systems can be
protected with valves that prevent wastewater from backing up into the home.
9-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
9 PROTECTING SERVICE EQUIPMENT
9.3.1 Floodwalls and Shields
Floodwalls and shields are typically components of dry floodproofing systems (Chapter 7) that are used to protect
entire buildings. However, if a building is wet floodproofed, these components can be used for the protection of
small areas within a building that contain service equipment that cannot be elevated or relocated. For example,
you can build a concrete floodwall that surrounds one or more pieces of service equipment, such as a furnace and
water heater (Figure 9-3).
If the expected flood depth is less than about 12 inches, the floodwall could be low enough that you could step
over it to reach the protected equipment. A higher floodwall can include an opening equipped with a removable
shield, as shown in Figure 9-3, to permit easy access to the protected equipment. In this example, the shield does
not interfere with the normal operation of the equipment, so it should be left in place and removed only when
necessary to service the equipment. Leaving the shield in place allows the barrier to function without human
intervention.
In general, barriers and shields of the type shown in Figure 9-3 are practical only when flood depths are less than
about 3 feet. The greater hydrostatic pressure exerted by deeper water requires barriers and shields that are more
substantial, have more complex designs, and are, therefore, more expensive. As discussed in Chapter 8, all flood-
walls should provide at least 1 foot of freeboard above the expected flood elevation.
Regardless of the height of the barrier, the area it protects should
be equipped with a sump pump that will remove any water that
accumulates through seepage.
9.3.2 Anchors and Tiedowns
Anchors and tiedowns are used primarily for aboveground stor-
age tanks (ASTs) that are not el-evated above the flood level and
for underground storage tanks (USTs). Both types of tanks are
extremely vulnerable to flotation. Floodwaters and debris im-
pact forces act directly on ASTs, and USTs can be forced out
Figure 9-3. Water heater
and furnace protected by
a concrete floodwall with
opening and gasketed shield.
CROSS REFERENCE
For more information about anchor-
ing fuel storage tanks, refer to FEMA
348, Protecting Building Utilities
from Flood Damage (1999), and the
FEMA Fact Sheet series Protect Your
Property from Flooding, Anchor Fuel
Tanks (2011).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-9
PROTECTING SERVICE EQUIPMENT 9
of the ground by the buoyancy force of saturated soils. When
either type of tank is displaced, its connections can be severed
and the escaping fuel can cause hazardous conditions.
ASTs can be anchored with metal straps or cables that cross over
the tank and connect to ground anchors. The length and type
of ground anchor you need depends largely on the type of soil
at the site. A design professional can advise you about anchors.
Another way to anchor an AST is to embed its legs in a concrete
slab (Figure 9-4).
Ground anchors can also be used for USTs. The anchoring meth-
od involves excavating the soil above the tank, placing steel
I-beams across it, and connecting them to ground anchors.
Again, check with a design professional concerning the required
size and type of anchor. USTs can also be anchored with a concrete slab similar to the one shown in Figure 9-4.
Installing the slab involves excavating around the tank and removing it temporarily while the slab is poured.
Another alternative is to excavate down to the tank and pour a concrete slab on top, ensuring not to cover access
openings.
On all tanks below the flood level, both aboveground and underground, flexible connections must be used
between the tank and the supply line. Also, the vent and filler tubes must extend above the flood protection eleva-
tion (Figure 9-4). If you have adequate warning of an impending flood, top off the tank. A full tank will be less
susceptible to corrosion from accumulated moisture and will be heavier and better able to resist buoyancy.
Figure 9-4. Anchoring a fuel
storage tank with a concrete
slab.
NOTE
Be especially careful when anchoring
storage tanks or other service equip-
ment in floodways, Zone V areas,
and other high-risk areas. Consider
the effects of high-velocity flows,
wave action, fast moving floodborne
debris, and extensive erosion and
scour wherever these hazards are
likely to occur.
9-10 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
9 PROTECTING SERVICE EQUIPMENT
Although anchoring is particularly important for storage tanks, remember that the levels of future floods can rise
higher than expected and inundate service equipment that you have elevated, relocated, or protected in place. For
this reason, service equipment should be anchored whenever possible so that it will remain in place when acted
on by flood forces. Anchorage systems should be designed assuming a worst-case scenario of an empty tank.
9.3.3 Backflow Valves
Flooding can inundate and overload sanitary sewer systems and
combined sanitary/storm sewer systems. As a result, water can
flow backward through sewer lines and out through toilets or
drains. The best solution to this problem is usually to install a
backflow valve. These valves include check valves, gate valves,
and dual backflow valves.
Check valves operate without human intervention. Under nor-
mal conditions, they allow wastewater to flow from the home to
the main sewer line. When flooding causes the flow to reverse, a
flap or other check mechanism in the valve prevents water from
flowing back into the home. A disadvantage of check valves is
that they can become blocked open by debris and fail to operate.
For this reason, check valves must be inspected regularly and cleaned as necessary.
Gate valves are manually operated, provide a better seal, and are unlikely to be blocked open. However, they are
more expensive than check valves and require human intervention.
The third alternative is dual backflow valves, which combine the benefits of the check valve and the gate valve.
As the most expensive of the three valve types, the dual backflow valve should be considered primarily for use in
homes subject to repeated backflow flooding. Gate valves and dual backflow valves are usually installed outside
the home in a valve pit (Figure 9-5). A licensed plumber should install any check valve system in compliance with
local codes. Some current community codes only allow use of dual check valve systems.
Figure 9-5. Example of an
exterior backflow valve
installed in a valve pit.
WARNING
The installation of backflow valves
and other plumbing modifications is
usually regulated by State and local
building codes. Some municipali-
ties may prohibit the use of backflow
valves. A plumber or contractor licen-
sed to work in your area will know
about the code requirements that
apply to your retrofitting project.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING A-1
Appendix A
Bibliography and Sources of Information
FEMA and other organizations have produced many documents about floodproofing and flood hazard mitigation.
Those listed below provide information that may be useful to a homeowner who is thinking about undertaking a
retrofitting project or to a homeowner’s designer or builder.
ASCE (American Society of Civil Engineers). 2005a. Flood Resistant Design and Construction. ASCE Standard ASCE 24-05.
ASCE. 2010. Minimum Design Loads for Buildings and Other Structures. ASCE Standard ASCE 7-10.
FEMA (Federal Emergency Management Agency). 1999. Protecting Building Utilities from Flood Damage. FEMA 348.
FEMA. 2000. Above the Flood: Elevating Your Floodprone House. FEMA P-347.
FEMA. 2005. Reducing Damage from Localized Flooding. FEMA 511.
FEMA. 2006. Homebuilders’ Guide to Earthquake-Resistant Design and Construction. FEMA 232.
FEMA. 2009. Recommended Residential Construction for Coastal Areas: Building on Strong and Safe Foundations. FEMA P-550.
FEMA. 2010a. Protecting Utilities. FEMA 499, Fact Sheet No. 8.3.
FEMA. 2010b. Substantial Improvement/Substantial Damage Desk Reference. FEMA P-758.
FEMA. 2010c. Wind Retrofit Guide for Residential Buildings. FEMA P-804.
FEMA. 2011a. Anchor Fuel Tanks: Protect Your Property from Flooding. FEMA Fact Sheet.
FEMA. 2011b. Coastal Construction Manual: Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining
Residential Buildings in Coastal Areas. FEMA P-55, Fourth Edition.
FEMA. 2012a. Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures. FEMA P-259, Third Edition.
A-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
A BIBLIOGRAPHY AND SOURCES OF INFORMATION
FEMA. 2012b. Minimizing Damage to Electrical Service Components. Hurricane Isaac Recovery Advisory No. 2.
FEMA. 2012c. Minimizing Wind and Water Intrusion by Covering the Underside of Elevated Buildings. Hurricane Isaac Recovery
Advisory No. 1.
FEMA. 2013a. Cleaning Flooded Buildings. Hurricane Sandy Recovery Fact Sheet No. 1.
FEMA. 2013b. Designing for Flood Levels Above the BFE After Hurricane Sandy. Hurricane Sandy Recovery Advisory No. 5.
FEMA. 2013c. Foundation Requirements and Recommendations for Elevated Homes. Hurricane Sandy Recovery Fact Sheet No. 2.
FEMA. 2013d. Hurricane Sandy in New Jersey and New York. FEMA P-942.
FEMA. 2013e. Reducing Flood Risk and Flood Insurance Premiums for Existing Residential Buildings in Zone A. Hurricane Sandy
Recovery Advisory No. 7.
FEMA. 2013f. Restoring Mechanical, Electrical, and Plumbing Systems. Hurricane Sandy Recovery Advisory No. 3.
FEMA. 2013g. Unified Hazard Mitigation Assistance Guidance.
FM Approvals. 2006. Approval Standard for Flood Abatement Equipment. FM Standard 2510.
International Code Council. 2012. 2012 International Building Code (IBC 2012).
International Code Council. 2012. 2012 International Existing Building Code (IEBC 2012).
International Code Council. 2012. 2012 International Residential Code (IRC 2012).
OSHA (Occupational Safety and Health Administration). 2012a. Hurricane Sandy Cleanup PPE Matrix. Fact Sheet,
OSHA-FS-3612.
OSHA. 2012b. Mold Hazards During Hurricane Sandy Cleanup. Fact Sheet, OSHA-FS-3619.
Federal Emergency Management Agency – Technical Bulletin Links
Openings in Foundation Walls and Walls of Enclosures, Technical Bulletin 1, August 2008,
http://www.fema.gov/media-library/assets/documents/2644.
Flood Damage-Resistant Materials Requirements, Technical Bulletin 2, August 2008,
http://www.fema.gov/media-library/assets/documents/2655.
Non-Residential Floodproofing – Requirements and Certification. Technical Bulletin 3, April 1993,
https://www.fema.gov/media-library/assets/documents/3473.
Free-of-Obstruction Requirements, Technical Bulletin 5, August 2008,
http://www.fema.gov/media-library/assets/documents/3490.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING A-3
BIBLIOGRAPHY AND SOURCES OF INFORMATION A
Wet Floodproofing Requirements, FIA-TB-7, December 1993,
http://www.fema.gov/media-library/assets/documents/3503.
U.S. Army Corps of Engineers
Tests of Brick-Veneer Walls and Closures for Resistance to Floodwaters, May 1978.
http://www.dtic.mil/docs/citations/ADA064860.
Structural Integrity of Brick-Veneer Buildings, 1978. http://www.dtic.mil/docs/citations/ADA055972.
Systems and Materials to Prevent Floodwaters from Entering Buildings, May 1985.
http://www.dtic.mil/dtic/tr/fulltext/u2/a156050.pdf.
USACE National Flood Proofing Committee: Flood Proofing Tests – Tests of Materials and Systems for Flood Proofing Structures,
August 1988. http://cdm16021.contentdm.oclc.org/cdm/ref/collection/p16021coll11/id/6.
Flood Proofing – How to Evaluate Your Options, July 1993. http://www.usace.army.mil/Library/Pages/default.aspx.
For additional information about natural hazards and hazard mitigation, visit the Internet sites listed below:
American Red Cross
http://www.redcross.org
Applied Technology Council
http://www.atcouncil.org
Association of State Floodplain Managers
http://www.floods.org
Disaster Research Center, University of Delaware
http://www.udel.edu/DRC/
Federal Alliance for Safe Homes
http://www.flash.org/
Federal Emergency Management Agency
http://www.fema.gov
Hazard Reduction and Recovery Center (HRRC), Texas A&M
http://archone.tamu.edu/hrrc/
Insurance Institute for Business & Home Safety (IBHS)
http://www.disastersafety.org/
National Association of Home Builders
http://www.nahb.org/
A-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
A BIBLIOGRAPHY AND SOURCES OF INFORMATION
National Flood Insurance Program (NFIP)
http://www.floodsmart.gov/floodsmart/
National Geophysical Data Center
http://www.ngdc.noaa.gov
National Information Service for Earthquake Engineering, University of California at Berkeley
http://nisee.berkeley.edu
Natural Hazards Center at the University of Colorado, Boulder, Colorado
http://www.colorado.edu/hazards
StromStruck – A Tale of Two Homes
http://www.stormstruck.com/
U. S. Army Corps of Engineers – National Nonstructural Flood Proofing Committee
http://www.usace.army.mil/Missions/CivilWorks/ProjectPlanning/nfpc.aspx
U.S. Department of Housing and Urban Development (HUD) – Office of Policy Development and Re-
search (PDNR)
http://www.huduser.org/portal/index.php
U. S. Geological Survey – Earthquake Hazards Program
http://quake.wr.usgs.gov
U. S. Natural Resources Conservation Service
http://www.nrcs.usda.gov
Wind Engineering Research Center, Texas Tech University
http://www.depts.ttu.edu/weweb/
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-1
Appendix B
Glossary
Many of the terms defined here are also defined in the margins of pages on which they first appear or explained
in the body of the text.
Acquisition and demolition – The voluntary process by which your State or local government purchases an
existing at-risk building, and, typically, the underlying land; demolishes the building; and converts the land to
open space. The land is then maintained as open space and used to restore and/or conserve the natural floodplain
functions.
Active retrofitting method – Method that will not function as intended without human intervention. See “pas-
sive retrofitting method.”
Adjacent grade – See “lowest adjacent grade (LAG).”
Alluvial fan flooding – Flooding that occurs on the surface of an alluvial fan (or similar landform) that originates
at the apex of the fan and is characterized by high-velocity flows; active processes of erosion, sediment transport,
and deposition; and unpredictable flow paths.
Armor – To protect fill slopes, such as the sides of a levee, by covering them with erosion-resistant materials such
as rock or concrete.
Backfill – To fill in a hole with the soil removed from it or with other material, such as soil, gravel, or stone.
Backflow valve – See “check valve.”
Barrier systems – See “floodwall” or “levees.”
Base flood – Flood that has a 1 percent probability of being equaled or exceeded in any given year (formerly
known as the 100-year flood).
B-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
B GLOSSARY
Base flood elevation (BFE) – The elevation of the base flood relative to the datum specified on a community’s
Flood Insurance Rate Map (FIRM). The elevation is shown on the FIRM for Zones AE, AH, A1–A30, AR, AR/A, AR/
AE, AR/A1–A30, AR/AH, AR/AO, V1–V30, and VE and indicates the water surface elevation resulting from a flood
that has a 1 percent chance of equaling or exceeding that level in any given year. The BFE is the National Flood
Insurance Program’s (NFIP’s) minimum elevation to which the lowest floor of a building must be elevated or
floodproofed (Zone A). In Zone V, the bottom of the lowest horizontal structural member must be elevated to or
above the BFE; floodproofing is not permitted in Zone V. Many SFHAs are shown on FIRMs without BFEs; in these
areas, community officials and permit applicants are required to obtain and use information from other sources,
or must estimate or develop BFEs at specific locations.
Basement – Any area of the building having its floor subgrade (below ground level) on all sides.
Benchmark – A reference point established by a survey with a precisely known relationship to a datum.
Building envelope – The entire exterior surface of a building (including cladding, roofing, exterior walls, doors,
and windows) that encloses or envelopes the space within.
Buoyancy – The upward hydrostatic force that floodwater exerts on the underside of submerged members (such
as floor slabs, walls and footings) of homes that have enclosed spaces below the flood level.
Cast-in-place concrete – Concrete poured and formed at the construction site.
Check valve – Valve that allows water to flow in one direction, but automatically closes when the direction of
flow is reversed.
Closure – Shield made of strong material, such as metal or wood, used to temporarily close openings in levees,
floodwalls, and dry floodproofed buildings.
Coastal A Zone – The portion of the coastal SFHA referenced by building codes and standards, where base flood
wave heights are between 1.5 and 3 feet, and where wave characteristics are deemed sufficient to damage many
NFIP-compliant structures on shallow or solid wall foundations.
Coastal High Hazard Areas – SFHAs along the coasts that have additional hazards due to wind and wave action.
These areas are identified on FIRMs as Zones V, V1–V30, and VE.
Compaction – In construction, the process by which the density of earth fill is increased so that it will provide a
sound base for a building or other structure.
Crawlspace – Type of foundation in which the lowest floor of a home is suspended above the ground on continu-
ous foundation walls.
Cribbing – A temporary framework that usually consists of criss-crossed timbers that provide temporary struc-
tural support. Cribbing usually consists of layers of heavy timber.
Cutoff trench – A core located below the base of a dam or levee structure. The trench is filled with an impervious
material, such as clay, to form a watertight barrier to prevent under-levee seepage.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-3
GLOSSARY B
Datum – An elevation datum is an arbitrary surface that serves as a common reference for the elevations of points
above or below it. Elevations are expressed in terms of feet, meters, or other units of measure and are identified as
negative or positive, depending on whether they are above or below the datum. Three common elevation datums are
mean sea level (msl), NGVD, and NAVD.
Debris – Materials carried by floodwaters, including objects of various sizes and suspended soils.
Demolition – The act or process of reducing a structure, as defined by State or local code, to a collapsed state.
Design capacity – For drainage systems, the volume of water that a channel, pipe, or other drainage line is de-
signed to convey.
Design flood elevation (DFE) – The elevation of the design flood relative to the datum specified on the communi-
ty’s FIRM. The design flood is associated with the greater of the area subject to the base flood or the area designated
as a flood hazard area on a community flood hazard map. The I-Codes, ASCE 7, and ASCE 24 use the term DFE. In
most communities, the DFE is identical to the BFE. Communities may designate a design flood (or DFE) in order
to regulate based on a flood of record, to account for future increases in flood levels based on upland develop-
ment, or to incorporate freeboard.
Dry floodproofing – Protecting a building through a combination of measures in order to prevent the entrance
of floodwaters. Structural components of the building must have the capacity to resist the resulting flood loads.
Duration – The measure of how long a flood lasts. Duration can also refer to how long it takes for a creek, river,
bay, or ocean to return to its normal level.
Elevation – In retrofitting, the process of physically raising an existing building so that it is above the height of
a given flood.
Elevation datum – Arbitrary surface that serves as a common reference for the elevations of points above or be-
low it. Elevations are expressed in terms of feet, meters, or other units of measure and are identified as negative
or positive, depending on whether they are above or below the datum. Three common datums are mean sea level
(msl), National Geodetic Vertical Datum (NGVD), and North American Vertical Datum (NAVD).
Enclosure – That portion of an elevated building below the lowest elevated floor that is either partially or fully
shut in by rigid walls.
Erosion – A general lowering of the ground surface over a wide area.
Federal Emergency Management Agency (FEMA) – Agency within the Department of Homeland Security (DHS)
that administers the NFIP. The NFIP is the Federal program, created by Congress in 1968, that makes flood insur-
ance available in communities that adopt and enforce floodplain management ordinances or laws that meet the
minimum requirements of the NFIP regulations.
Federal Insurance and Mitigation Administration (FIMA) – Component of FEMA directly responsible for ad-
ministering the flood insurance aspects of the NFIP.
Fill – Material such as soil, gravel, or stone that is dumped in an area to increase the ground elevation. Fill is usu-
ally placed in layers and each layer compacted (see “compaction”).
B-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
B GLOSSARY
Flap valve – See “check valve.”
Flash Flood – A flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours.
A flash flood rises and falls very quickly and is usually characterized by high flow velocities.
Flood – Under the NFIP, “a general and temporary condition of partial or complete inundation of normally dry
land areas” from: 1) the overland flow of a lake, river, stream, ditch, etc.; 2) the unusual and rapid accumulation
or runoff of surface waters; and 3) mudflows or the sudden collapse of shoreline land.
Flood damage-resistant material – Any building product (material, component, or system) capable of with-
standing direct and prolonged contact with floodwaters without sustaining significant damage.
Flood depth – Height of floodwaters above the surface of the ground at a given point.
Flood elevation – Water surface elevation of floodwaters based on a given elevation datum.
Flood frequency – Probability, expressed as a percentage, that a flood of a given size will be equaled or exceeded
in any given year. For example, the 1 percent annual chance flood has a 1 percent chance (1 in 100) of being
equaled or exceeded in any given year.
Flood protection elevation – The elevation to which you choose to protect your home. Although a flood protec-
tion elevation less than the DFE is feasible, FEMA recommends protecting your home to at least the DFE.
Floodplain – Any area susceptible to inundation by water from any source. See “regulatory floodplain.”
Floodplain management – Program of corrective and preventive measures for reducing flood damage, including
flood control projects, floodplain management regulations, floodproofing or retrofitting of buildings, and emer-
gency preparedness plans.
Floodproofing – Any combination of structural or nonstructural changes or adjustments included in the design,
construction, or alteration of a building that reduce or eliminate flood damage to the building and its contents.
See “dry floodproofing” and “wet floodproofing.”
Floodwall – Flood barrier constructed of manmade materials, such as concrete or masonry, to keep water away
from or out of a specified area.
Floodway – Portion of the SHFA that must be reserved to prevent significant increases in flood elevations. The
flood hazard is usually greater in the floodway (higher flood depths and velocities) than in the surrounding areas
of the SFHA, referred to as the “flood fringe.”
Flow velocity – Speed at which water moves during a flood. Velocities usually vary across the floodplain and are
generally greatest near the channel and lowest near the edges of the floodplain.
Footing – The base of a foundation, usually made of concrete and sometimes reinforced with steel bars. Founda-
tion walls are supported on continuous footings; separate foundation members, such as piers, are supported on
individual footings.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-5
GLOSSARY B
Footprint – The land area a house covers. This area is equal to the length of the home multiplied by its width. The
footprint is not necessarily equal to the total square footage of the home.
Frame Construction – A type of construction in which a supportive framework forms the primary structural ele-
ment of a building. In residential construction, the framework typically consists of wood or steel members.
Freeboard – An added margin of safety, expressed in feet above a specific flood elevation, usually the BFE. In States
and communities that require freeboard, buildings are required to be elevated or floodproofed to the higher eleva-
tion. For example, if a community adopts a 2-foot freeboard, buildings are required to be elevated or floodproofed
to 2 feet above the BFE.
Frequency – See “flood frequency.”
Grade beam – In a slab foundation, a support member cast as an integral part of the slab, as opposed to a sepa-
rate footing.
Hazard mitigation – Sustained action taken to reduce or eliminate long-term risk to people and property from
hazards such as floods, hurricanes, earthquakes, and fires.
Human intervention – Any action that a person must take to enable a flood protection measure to function as
intended. This action must be taken every time flooding threatens.
High-velocity flow – During a design flood or lesser conditions, water movement adjacent to structures and/or
foundations with flow velocities greater than 10 feet per second.
Hydrodynamic force – Force exerted by moving water.
Hydrostatic force – Force exerted by water at rest, including lateral pressure on walls and uplift (buoyancy) on
floors.
Ice Jam – Accumulation of floating ice fragments that causes the bridging or damming of a channel or stream.
Impervious soils – Soils that resist penetration by water.
Intensity of rainfall – The amount of rain that falls during a given amount of time. It is usually expressed in inch-
es of rainfall per hour. The greater the number of inches per hour, the greater the intensity.
Jetting – A process in which the hole for the installation of a pile is made by a high-pressure stream of water from
a nozzle attached to the bottom of the pile.
Letter of Map Amendment (LOMA) – Occasionally, a small area is inadvertently shown to be within the SFHA on
a FIRM, even though the ground is at or above the BFE. If this occurs, an individual property owner may submit
survey information to FEMA and request that FEMA issue a document that officially removes a property from the
SFHA, called a Letter of Map Amendment.
Levee – Manmade barrier, usually constructed of compacted soil, designed to contain, control, or divert the flow
of flood water from a specified area.
B-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
B GLOSSARY
Local officials – Community employees who are responsible for floodplain management, zoning, permitting,
building code enforcement, and building inspection.
Lowest adjacent grade (LAG) – The lowest ground surface that touches any of the exterior walls of a home. The
LAG is determined at the pier or post of an attached deck or porch if the elevation is lower than the point where
soil touches the foundation of the building.
Lowest floor – Floor of the lowest enclosed area within a building, including a basement. The only exception is
an enclosed area below an elevated building, but only when the enclosed area is used solely for parking, building
access, or storage and is compliant with relevant regulations
Limit of Moderate Wave Action (LiMWA) – A line indicating the limit of the 1.5-foot wave height during the
base flood. FEMA requires new flood studies in coastal areas to delineate the LiMWA.
Minimal Wave Action (MiWA) area – The portion of the coastal Special Flood Hazard Area where base flood
wave heights are less than 1.5 feet.
Moderate Wave Action (MoWA) area – see Coastal A Zone.
Manufactured home – A prefabricated frame home constructed on a transportable frame that can be placed on a
permanent or temporary foundation (subject to Federal and State standards).
Masonry – Walls constructed of brick, stone, or concrete block.
Masonry veneer – Nonstructural, decorative, exterior layer of brick, stone, or concrete block added to the walls
of a building.
Mean sea level (msl) – A tidal elevation datum based on data collected over a 19-year tide cycle.
Mitigation reconstruction – The construction of an improved, elevated building on the same site where an exist-
ing building and/or foundation has been partially or completely demolished or destroyed.
Modular home – A frame home assembled on site on a permanent foundation from separate sections manufac-
tured elsewhere (subject to local building codes).
National Geodetic Vertical Datum (NGVD) – A geodetic elevation datum previously used by FEMA for the de-
termination of flood elevations. While NGVD has been updated to the NAVD datum on many FIRMs, it is still the
datum referenced on many of the older FIRMs.
North American Vertical Datum (NAVD) – A geodetic elevation datum currently used by FEMA for the deter-
mination of flood elevations.
Passive retrofitting method – Method that operates automatically, without human intervention. See “active ret-
rofitting method.”
Permeable soils – Soils through which water can easily penetrate and flow.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-7
GLOSSARY B
Pier – Vertical support member of masonry or cast-in-place concrete that is designed and constructed to func-
tion as an independent structural element in supporting and transmitting both building loads and environmental
loads to the ground.
Piling – Vertical support member of wood, steel, or precast concrete that is driven or jetted into the ground and
supported primarily by friction between the pilings and the surrounding earth. Pilings often cannot act as inde-
pendent support units and therefore are often braced with connections to other pilings.
Post – Long vertical support member of wood or steel set in holes that are backfilled with compacted material.
Posts often cannot act as independent support units and, therefore, are often braced with connections to other
posts.
Precast concrete – Concrete materials such as posts, beams, and blocks that are brought to the construction site
in finished form.
Prolonged contact – At least 72 hours of contact with floodwaters.
Rates of rise and fall – How rapidly the elevation of the water rises and falls during a flood.
Regulatory floodplain – Flood hazard area within which a community regulates development, including new
construction, the repair of Substantially Damaged buildings, and Substantial Improvements to existing buildings.
In communities participating in the NFIP, the regulatory floodplain must include at least the area inundated by the
base flood, also referred to as the SFHA.
Reinforcement – Inclusion of steel bars in concrete members and structures to increase their strength.
Relocation – In retrofitting, the process of moving a home or other building to a new location outside the flood
hazard area.
Retrofitting – Making changes to an existing home or other building to protect it from flooding or other hazards.
Riprap – Pieces of rock or crushed stone added to the surface of a fill slope, such as the side of a levee, to prevent
erosion.
Saturated soils – Soils that have absorbed, to the maximum extent possible, water from rainfall or snowmelt.
Scour – A localized loss of soil, often around a foundation element.
Sealant – In retrofitting, a waterproofing material or substance used to prevent the infiltration of floodwater.
Service equipment – The utility systems, heating and cooling systems, and large appliances in a retrofitted home.
Significant damage – As it relates to flood-damage resistant materials, any damage requiring more than cosmetic
repair.
Slab-on-grade – Type of foundation in which the lowest floor of the home is formed by a concrete slab that sits
directly on the ground. The slab may be supported by independent footings or integral grade beams.
B-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
B GLOSSARY
Special Flood Hazard Area (SFHA) – An area delineated on a FIRM as being subject to inundation by the base
flood, designated Zone A, AE, A1–A30, AR, AO, AH, A99, V, VE, or V1–V30.
Storm surge – Water pushed toward the shore by the force of the winds swirling around a storm. It is the greatest
cause of loss of life due to hurricanes..
Subgrade – Below the level of the ground surface.
Substantial Damage – Damage to a building, regardless of the cause, is considered Substantial damage if the cost
of restoring the building to its before-damage condition would equal or exceed 50 percent of the market value of
the building before the damage occurred
Substantial Improvement – Under the NFIP, an improvement of a building (such as reconstruction, rehabilita-
tion, or an addition) is considered a Substantial Improvement if its cost equals or exceeds 50 percent of the market
value of the building before the start of construction of the improvement.
Substantially impermeable – A wall is considered substantially impermeable if it limits water accumulation to 4
inches in a 24 hour period. In addition, sump pumps are required to control any seepage and flood-resistant ma-
terials must be used in all areas where seepage is likely to occur. This standard is the minimum requirement; lower
seepage rates are possible and strongly encouraged by FEMA, particularly in new construction.
Sump pump – Device used to remove water from seepage or rainfall that collects in areas protected by a levee,
floodwall, or dry floodproofing. In addition, a sump pump is often part of a standard home drainage system that
removes water that collects below a basement slab floor.
Tsunami – Large, rapidly moving sea waves produced by an undersea earth movement (earthquakes, crustal dis-
placements or landslides) or volcanic eruption.
Underseepage – Water that migrates downward along the sealed walls of a home and then under the foundation.
Veneer – See “masonry veneer.”
Walkout-on-grade basement – Basement whose floor is at ground level on at least one side of a home. The term
“walkout” is used because most basements of this type have an outside door or doors (entry door, garage door, or
both) at ground level. A walkout-on-grade basement is not considered a basement under the NFIP. See “basement.”
Watershed – The land area that drains water to a particular stream, river, or lake. It is a land feature that can be
identified by tracing a line along the highest elevations between two areas on a map, often a ridge.
Wave action – The characteristics and effects of waves that move inland from an ocean, bay, or other large body
of water. Large, fast-moving waves can cause extreme erosion and scour, and their impact on buildings can cause
severe damage.
Wet floodproofing – The use of flood-damage-resistant materials and construction techniques to minimize flood
damage to areas below the flood protection level of a building, which is intentionally allowed to flood. Usually,
only enclosed areas used for parking, building access, or storage are wet floodproofed.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING C-1
Appendix C
FEMA Offices
The addresses and telephone numbers of FEMA Headquarters and the 10 FEMA Regional Offices are listed below.
Staff members of the Regional Office for your area can give you more information about retrofitting, hazard miti-
gation, and the National Flood Insurance Program.
C-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
C FEMA REGIONAL OFFICES
FEMA HEADQUARTERS500 C Street, SW
Washington, DC 20472
(202) 646-2500, (800) 621-FEMA (3362)
TTY: (800) 462-7585
REGION I – CT, MA, ME, NH, RI, VT
99 High Street, Sixth Floor
Boston, MA 02110
(877) 336-2734
REGION II – NJ, NY, PR, VI
26 Federal Plaza, Suite 1337
New York, NY 10278-0002
(212) 680-3600
REGION III – DC, DE, MD, PA, VA, WV
615 Chestnut Street
One Independence Mall, Sixth Floor
Philadelphia, PA 19106-4404
(215) 931-5500
REGION IV – AL, FL, GA, KY, MS, NC, SC, TN
3003 Chamblee Tucker Road
Atlanta, GA 30341-4112
(770) 220-5200
REGION V – IL, IN, MI, MN, OH, WI
536 South Clark Street, Sixth Floor
Chicago, IL 60605-1521
(312) 408-5500
REGION VI – AR, LA, NM, OK, TX
Federal Regional Center
800 North Loop 288
Denton, TX 76209-3698
(940) 898-5399
REGION VII – IA, KS, MO, NE
9221 Ward Parkway, Suite 300
Kansas City, MO 64114-3372
(816) 283-7061
REGION VIII – CO, MT, ND, SD, UT, WY
Denver Federal Center
Building 710, Box 25267
Denver, CO 80255-0267
(303) 235-4800
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING C-3
FEMA REGIONAL OFFICES C
REGION IX – AZ, CA, HI, NV, American Samoa, Guam, Commonwealth of the Northern Mariana Islands,
Republic of the Marshall Islands, Federated States of Micronesia
1111 Broadway, Suite 1200
Oakland, CA 94607-4052
(510) 627-7100
REGION X – AK, ID, OR, WA
Federal Regional Center
130 228th Street, SW
Bothell, WA 98021-8627
(425) 487-4600
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-1
Appendix D
Alabama
Alabama Department of Community and
Economic Development
Office of Water Resources
401 Adams Avenue, Suite 434
P.O. Box 5690
Montgomery, AL 36103-5690
Phone: (334) 353-0853
http://www.adeca.alabama.gov/water/
Alaska
Alaska Department of Commerce, Community, and
Economic Development
550 West 7th Avenue, Suite 1770
Anchorage, AK 99501-3510
Phone: (907) 269-4583
Fax: (907) 269-4539
http://www.commerce.state.ak.us/
Arizona
Arizona Department of Water Resources
3550 North Central Avenue
Phoenix, AZ 85012-2105
Phone: (602) 771-8657
Fax: (602) 771-8686
http://www.azwater.gov/
NFIP State Coordinating Agencies
Arkansas
Arkansas Natural Resources Commission
101 East Capitol, Suite 350
Little Rock, AR 72201-3823
Phone: (501) 682-3969
Fax: (501) 682-3991
http://www.anrc.arkansas.gov/
California
California Department of Water Resources
3464 El Camino Avenue, Suite 200
Sacramento, CA 95821
Phone: (916) 574-1409
http://www.water.ca.gov/
Colorado
Colorado Water Conservation Board
1313 Sherman Street, Room 721
Denver, CO 80203
Phone: (303) 866-3441
Fax: (303) 861-4272
http://cwcb.state.co.us/
Connecticut
Department of Energy and Environmental
Protection
79 Elm Street
Hartford, CT 06106
Phone: (860) 424-3537
Fax: (860) 424-4075
http://www.ct.gov/dep/
D-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
D NFIP STATE COORDINATING AGENCIES
Delaware
Department of Natural Resources and
Environmental Control
89 Kings Highway
Dover, DE 19901
Phone: (302) 739-9921
Fax: (302) 739-6724
http://www.dnrec.delaware.gov
District of Columbia
District Department of the Environment
Watershed Protection Division
1200 First Street, 5th Floor
Washington, DC 20002
Phone: (202) 535-2248
Fax: (202) 535-1364
http://green.dc.gov/watershed
Florida
Division of Emergency Management
2555 Shumard Oak Boulevard
Tallahassee, Florida 32399-2100
Phone: (850) 922-4518
http://www.floridadisaster.org/
Georgia
Georgia Department of Natural Resources
4220 International Parkway, Suite 101
Atlanta, GA 30354
Phone: (404) 656-6382
Fax: (404) 675-1607
http://www.gadnr.org/
Guam
Guam Department of Public Works
542 North Marine Corps Drive
Upper Tumon, Guam 96913
Phone: (671) 646-3131
Fax: (671) 649-6178
http://www.dpw.guam.gov
Hawaii
Hawaii Department of Land and Natural Resources
1151 Punchbowl Street
P.O. Box 221
Honolulu, HI 96809
Phone: (808) 587-0267
Fax: (808) 587-0283
http://www.state.hi.us/dlnr/docare/
Idaho
Idaho Department of Water Resources
322 East Front Street
Boise, ID 83720
Phone: (208) 287-4928
http://www.idwr.idaho.gov/
Illinois
Illinois Department of Natural Resources
Office of Water Resources
One Natural Resources Way
Springfield, IL 62702-1271
Phone: (217) 782-4428
Fax: (217) 785-5014
http://dnr.state.il.us/OWR/
Indiana
Indiana Department of Natural Resources
402 West Washington Street, Room W264
Indianapolis, IN 46204-2748
Phone: (317) 234-1107
Fax: (317) 233-4579
http://www.state.in.us/dnr/
Iowa
Iowa Department of Natural Resources
502 East 9th Street
Des Moines, IA 50319
Phone: (515) 281-8942
Fax: (515) 281-8895
http://www.iowadnr.com/
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-3
NFIP STATE COORDINATING AGENCIES D
Kansas
Kansas Department of Agriculture
109 SW 9th Street, 2nd Floor
Topeka, KS 66612-1283
Phone: (785) 296-5440
Fax: (785) 296-4835
http://www.ksda.gov/
Kentucky
Kentucky Division of Water
200 Fair Oaks Lane, 4th Floor
Frankfort, KY 40601
Phone: (502) 564-3410
Fax: (502) 564-9899
http://www.water.ky.gov/
Louisiana
Louisiana Department of Transportation
and Development
Public Works and Water Resources Division
Floodplain Management Section
1201 Capitol Access Road
P.O. Box 94245
Baton Rouge, LA 70804-9245
Phone: (225) 274-4354
Fax: (225) 274-4351
http://www.dotd.state.la.us/
Maine
Maine Department of Agriculture, Conservation
and Forestry
Floodplain Management Program
93 State House Station, 17 Elkins Lane
Augusta, ME 04333-0038
Phone: (207) 287-8063
Fax: (207) 287-2353
http://www.state.me.us/spo/
Maryland
Maryland Department of the Environment
Water Management Administration
1800 Washington Boulevard, Suite 430
Baltimore, MD 21230
Phone: (410) 537-3775
Fax: (410) 537-3751
http://www.mde.state.md.us/
Massachusetts
Massachusetts Department of Conservation
and Recreation
Flood Hazard Management
251 Causeway Street, Suite 800
Boston, MA 02114
Phone: (617) 626-1406
Fax: (617) 626-1349
http://www.mass.gov/dcr/
Michagan
Michigan Department of Environmental Quality
525 West Allegan Street
P.O. Box 30458
Lansing, MI 48909-7958
Phone: (517) 335-3448
http://www.michigan.gov/deq
Minnesota
Minnesota Department of Natural Resources
500 LaFayette Road, Box 32
St. Paul, MN 55515-4032
Phone: (651) 259-5713
Fax: (651) 296-0445
http://www.dnr.state.mn.us/
Mississippi
Mississippi Emergency Management Agency
Office of Mitigation
1 Mema Drive
P.O. Box 5644
Pearl, MS 39208
Phone: (601) 933-6610
Fax: (601) 933-6805
http://www.msema.org/
Missouri
Missouri State Emergency Management Agency
2303 Militia Drive
P.O. Box 116
Jefferson City, MO 65101
Phone: (573) 526-9135
http://sema.dps.mo.gov/
D-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
D NFIP STATE COORDINATING AGENCIES
Montana
Montana Department of Natural Resources
and Conservation
Floodplain Management Program
1424 9th Avenue
Helena, MT 59620-1601
Phone: (406) 444-6654
Fax: (406) 444-0533
http://dnrc.mt.gov/wrd/water_op/floodplain/default.
asp
Nebraska
Nebraska Department of Natural Resources
301 Centennial Mall South
Lincoln, NE 68509-4876
Phone: (402) 471-3932
Fax: (402) 471-2900
http://www.dnr.ne.gov/
Nevada
Nevada Division of Water Resources
901 South Stewart Street, Suite 2002
Carson City, NV 89701
Phone: (775) 684-2847
http://water.nv.gov/
New Hampshire
New Hampshire Office of Energy and
Planning
4 Chenell Drive, 2nd Floor
Concord, NH 03301
Phone: (603) 271-1762
Fax: (603) 271-2615
http://www.nh.gov/oep/
New Jersey
Department of Environmental Protection
401 East State Street
P.O. Box 420
Trenton, NJ 08625
Phone: (609) 292-2296
http://www.state.nj.us/dep/
New Mexico
New Mexico Department of Homeland Security
and Emergency Management
13 Bataan Boulevard
P.O. Box 27111
Santa Fe, NM 87508
Phone: (505) 476-9617
Fax: (505) 471-9695
http://www.nmdhsem.org/
New York
New York State Department of Environmental
Conservation
625 Broadway
Albany, NY 12233-3507
Phone: (518) 402-8146
Fax: (518) 402-9029
http://www.dec.ny.gov/
North Carolina
North Carolina Department of Public Safety
Division of Emergency Management
4218 Mail Service Center
Raleigh, NC 27699-4218
Phone: (919) 825-2317
http://www.ncem.org/
North Dakota
North Dakota State Water Commission
900 East Boulevard Avenue
Bismark, ND 58505-0850
Phone: (701) 328-4898
Fax: (701) 328-3747
http://www.swc.state.nd.us/
Ohio
Ohio Department of Natural Resources
2045 Morse Road, Building B-2
Columbus, OH 43229
Phone: (614) 265-6752
Fax: (614) 265-6767
http://www.dnr.state.oh.us/
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-5
NFIP STATE COORDINATING AGENCIES D
Oklahoma
Oklahoma Water Resources Board
3800 North Classen Boulevard
Oklahoma City, OK 73118
Phone: (918) 581-2924
Fax: (981) 581-2754
http://www.owrb.ok.gov/
Oregon
Department of Land Conservation Development
635 Capitol Street, NE, Suite 150
Salem, OR 97301-2540
Phone: (503) 373-0050
Fax: (503) 375-5518
http://www.lcd.state.or.us/
Pennsylvania
Pennsylvania Department of Community and
Economic Development
Commonwealth Keystone Building
400 North Street, 4th Floor
Harrisburg, PA 17120-0225
Phone: (717) 720-7445
Fax: (717) 783-1402
http://www.newpa.com/
Puerto Rico
Puerto Rico Planning Board
Centro Gubernamental Roberto Sanchez Vilella
P.O. Box 41119, Minillas Station
Santurce, PR 00940-90985
Phone: (787) 723-6200
http://www.jp.gobierno.pr/
Rhode Island
Rhode Island Emergency Management Agency
645 New London Avenue
Cranston, RI 02920
Phone: (401) 462-7048
Fax: (401) 944-1891
http://www.riema.ri.gov/
South Carolina
South Carolina Department of Natural Resources
Flood Mitigation Program
2762 Wildlife Lane
West Columbia, SC 29172
Phone: (803) 755-9335
Fax: (803) 755-0152
http://www.dnr.sc.gov/
South Dakota
South Dakota Division of Emergency Management
118 West Capitol Avenue
Pierre, SD 57501
Phone: (605) 773-3231
Fax: (605) 773-3580
http://www.oem.sd.gov/
Tennessee
Tennessee Department of Economic and
Community Development
Tennessee Tower Building
3211 North Roan Street
Johnson City, TN 37601
Phone: (423) 434-0158
Fax: (423) 434-0037
http://www.tn.gov/ecd/
Texas
Texas Water Development Board
1700 North Congress Avenue
P.O. Box 13231
Austin, TX 78711-3231
Phone: (512) 463-3509
Fax: (512) 475-2053
http://www.twdb.state.tx.us/
Utah
Utah Department of Public Safety
Division of Emergency Management
1110 State Office Building
Salt Lake City, UT 84114
Phone: (801) 538-3332
Fax: (801) 538-1676
http://www.cem.utah.gov/
D-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
D NFIP STATE COORDINATING AGENCIES
Vermont
Vermont Department of Environmental
Conservation
Water Quality Division, River Management
1 National Life Drive, Main 2
Montpelier, VT 05620
Phone: (802) 490-6152
http://www.anr.state.vt.us/dec/dec.htm
Virgin Islands
Virgin Islands Department of Planning and
Natural Resources
Cyril E. King Airport, Terminal Building 2nd Floor
St. Thomas, VI 00802
Phone: (340) 774-3320
http://www.dpnr.gov.vi/view-divisions
Virginia
Virginia Department of Conservation and
Recreation
Division of Dam Safety and Floodplain Management
600 East Main Street, 24th Floor
Richmond, VA 23219
Phone: (804) 371-6135
Fax: (804) 371-2630
http://www.dcr.virginia.gov/
Washington
Washington State Department of Ecology
P.O. Box 47600
300 Desmond Drive, SE
Olympia WA, 98504
Phone: (360) 407-6131
http://www.ecy.wa.gov/
West Virginia
West Virginia Division of Homeland Security
and Emergency Management
Capitol Building 1, Room EB-80
1900 Kanawha Boulevard
Charleston, WV 25305-0360
Phone: (304) 957-2571
Fax: (304) 965-3216
http://www.dhsem.wv.gov/
Wisconsin
Wisconsin Department of Natural Resources
P.O. Box 7921
Madison, WI 53707
Phone: (608) 266-3093
http://dnr.wi.gov/
Wyoming
Wyoming Office of Homeland Security
5500 Bishop Boulevard
Cheyenne, WY 82002
Phone: (307) 777-4907
Fax: (307) 635-6017
http://wyohomelandsecurity.state.wy.us/main.aspx
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-1
Appendix E
Alabama
Alabama Historical Commission
468 South Perry Street
P.O. Box 300900
Montgomery, AL 36130-0900
Phone: (334) 230-2690
http://www.preserveala.org
Alaska
Alaska Department of Natural Resources
Office of History and Archeology
550 West 7th Avenue, Suite 1310
Anchorage, AK 99501-3565
Phone: (907) 269-8721
Fax: (907) 269-8908
http://www.dnr.state.ak.us/parks/oha/index.htm
Arizona
Arizona State Parks
1300 West Washington
Phoenix, AZ 85007
Phone: (602) 542-4009
http://azstateparks.com/SHPO/index.html
State Historic Preservation Offices
Arkansas
Arkansas Historic Preservation Program
1500 Tower Building
323 Center Street
Little Rock, AR 72201
Phone: (501) 324-9880
Fax: (501) 324-9184
http://www.arkansaspreservation.org/
California
Office of Historic Preservation
Department of Parks and Recreation
1416 9th Street, Room 1442
P.O. Box 942896
Sacramento, CA 94296-0001
Phone: (916) 653-6624
Fax: (916) 653-9824
http://ohp.parks.ca.gov/
Colorado
Colorado Historical Society
Office of Archaeology and Historic Preservation
1300 Broadway
Denver, CO 80203
Phone: (303) 866-2136
Fax: (303) 866-2711
http://www.coloradohistory-oahp.org
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Connecticut
Connecticut Commission on Culture and Tourism
Historic Preservation and Museum Division
One Constitution Plaza, 2nd Floor
Hartford, CT 06103
Phone: (860) 256-2800
Fax: (860) 256-2811
http://www.cultureandtourism.org/cct/site/default.
asp
Delaware
Division of Historical and Cultural Affairs
21 The Green
Dover, DE 19901
Phone: (302) 736-7400
Fax: (302) 739-5660
http://www.state.de.us/shpo/index.htm
District of Columbia
Office of Planning
801 North Capitol Street, NE, Suite 4000
Washington, DC 20002
Phone: (202) 442-7600
http://planning.dc.gov/planning/site/default.asp
Florida
Division of Historical Resources
R. A. Gray Building
500 South Bronough Street
Tallahassee, FL 32399-0250
Phone: (850) 245-6333
http://www.flheritage.com/
Georgia
Department of Natural Resources
Historic Preservation Division
34 Peachtree Street, NW, Suite 1600
Atlanta, GA 30303
Phone: (404) 656-2840
Fax: (404) 657-1046
http://www.gashpo.org/
Hawaii
Department of Land and Natural Resources
State Historic Preservation Division
Kakuhihewa Building
601 Kamokila Boulevard, Suite 555
Kapolei, HI 96707
Phone: (808) 692-8015
Fax: (808) 692-8020
http://www.hawaii.gov/dlnr/hpd/hpgreeting.htm
Idaho
Idaho State Historical Society
2205 Old Penitentiary Road
Boise, ID 83712
Phone: (208) 334-2682
Fax: (208) 334-2774
http://www.idahohistory.net/shpo.html
Illinois
Illinois Historic Preservation Agency
1 Old State Capitol Plaza
Springfield, IL 62701-1507
Phone: (217) 782-4836
http://www.state.il.us/hpa/ps/
Indiana
Department of Natural Resources
Division of Historic Preservation and Archaeology
402 West Washington Street, Room W274
Indianapolis, IN 46204-2739
Phone: (317) 232-1646
http://www.state.in.us/dnr/historic/
Iowa
State Historical Society of Iowa
600 East Locust
Des Moines, IA 50319
Phone: (515) 281-6200
http://www.iowahistory.org
Kansas
Kansas State Historical Society
6425 SW 6th Avenue
Topeka, KS 66615
Phone: (785) 272-8681
Fax: (785) 272-8682
http://www.kshs.org/resource/buildings.htm
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-3
STATE HISTORIC PRESERVATION OFFICES E
Kentucky
Kentucky Heritage Council
300 Washington Street
Frankfort, KY 40601
Phone: (502) 564-7005
Fax: (502) 564-5820
http://heritage.ky.gov/
Louisiana
Division of Historic Preservation
Office of Cultural Development
Department of Culture, Recreation and Tourism
1051 North Third Street
P.O. Box 44247
Baton Rouge, LA 70804
Phone: (225) 342-8160
Fax: (225) 219-9772
http://www.crt.state.la.us/hp/
Maine
Maine Historic Preservation Commission
55 Capitol Street
65 State House Station
Augusta, ME 04333-0065
Phone: (207) 289-2132
http://www.state.me.us/mhpc/
Maryland
Maryland Historical Trust
100 Community Place
Crownsville, MD 21032-2023
Phone: (410) 514-7600
Fax: (410) 514-7678
http://mht.maryland.gov/
Massachusetts
Massachusetts Historical Commission
Department of the Commonwealth
220 Morrissey Boulevard
Boston, MA 02125-3314
Phone: (617) 727-8470
Fax: (617) 727-5128
http://www.sec.state.ma.us/mhc/mhcidx.htm
Michigan
Department of History, Arts, and Libraries
702 West Kalamazoo Street
P.O. Box 30738
Lansing, Michigan 48909-8238
Phone: (517) 241-2236
Fax: (517) 241-2930
http://www.michigan.gov/mshda/
Minnesota
Minnesota Historical Society
345 West Kellogg Boulevard
St. Paul, MN 55102-1906
Phone: (651) 259-3000
http://www.mnhs.org/
Mississippi
Department of Archives and History
200 North Street
P.O. Box 571
Jackson, MS 39205-0571
Phone: (601) 576-6850
Fax: (601) 576-6876
http://mdah.state.ms.us/
Missouri
Department of Natural Resources
205 Jefferson
P.O. Box 176
Jefferson City, MO 65102
Phone: (573) 751-7858
http://www.dnr.mo.gov/shpo/
Montana
State Historic Preservation Office
Montana Historical Society
1410 Eighth Avenue
Helena, MT 59620
Phone: (406) 444-7715
http://www.montanahistoricalsociety.com/shpo/de-
fault.asp
E-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
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Nebraska
Nebraska State Historical Society
P.O. Box 82554
1500 R Street
Lincoln, NE 68501
Phone: (402) 471-3270
http://www.nebraskahistory.org/
Nevada
Nevada State Historic Preservation Office
901 S. Stewart Street Suite 5004
Carson City, NV 89701
Phone: (775) 684-3448
http://nvshpo.org/
New Hampshire
Division of Historical Resources
19 Pillsbury Street, 2nd Floor
Concord, NH 03301-3570
Phone: (603) 271-3483
Fax: (603) 271-3433
http://www.nh.gov/nhdhr/
New Jersey
Historic Preservation Office
Department of Environmental Protection
401 E. State Street
P.O. Box 404
Trenton, NJ 08625-0404
Phone: (609) 984-0176
Fax: (609) 984-0578
http://www.state.nj.us/dep/hpo/
New Mexico
Historic Preservation Division
Department of Cultural Affairs
Bataan Memorial Building
407 Galisteo Street, Suite 236
Santa Fe, NM 87501
Phone: (505) 827-6320
Fax: (505) 827-6338
http://www.nmhistoricpreservation.org/
New York
State Historic Preservation Office
Peebles Island
P.O. Box 189
Waterford, NY 12188-0189
Phone: (518) 237-8643
http://nysparks.state.ny.us/shpo/
North Carolina
State Historic Preservation Office
Office of Archives and History
Department of Cultural Resources
109 East Jones Street
Raleigh, NC 27699
Phone: (919) 807-6570
Fax: (919) 807-6599
http://www.hpo.ncdcr.gov/
North Dakota
State Historical Society of North Dakota
Heritage Center
612 East Boulevard Avenue
Bismarck, ND 58505-0830
Phone: (701) 328-2672
Fax: (701) 328-3710
http://www.history.nd.gov/
Ohio
Ohio Historical Society
Historic Preservation Office
567 East Hudson Street
Columbus, OH 43211-1030
Phone: (614) 298-2000
Fax: (614) 298-2037
http://www.ohiohistory.org/resource/histpres/
Oklahoma
State Historic Preservation Office
Oklahoma Historical Society
2401 North Laird Avenue
Oklahoma City, OK 73105
Phone: (405) 521-6249
Fax: (405) 522-0816
http://www.okhistory.org/shpo/shpom.htm
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-5
STATE HISTORIC PRESERVATION OFFICES E
Oregon
Parks and Recreation Department
Heritage Programs
725 Summer Street NE, Suite C
Salem, OR 97301
Phone: (503) 986-0671
Fax: (503) 986-0793
http://egov.oregon.gov/OPRD/HCD/
Pennsylvania
Pennsylvania Historical and Museum Commission
300 North Street
Harrisburg, PA 17120
Phone: (717) 787-3362
Fax: (717) 783-9924
http://www.portal.state.pa.us/portal/server.
pt?open=512&mode=2&objID=1426
Puerto Rico
Calle Norzagaray Final Cuartel de Ballaja, 3er Piso
San Juan, PR 00906-6581
Phone: (787) 721-3737
Fax: (787) 721-3773
http://www.gobierno.pr/OECH/index.htm
Rhode Island
Rhode Island Historical Preservation and
Heritage Commission
Old State House
150 Benefit Street
Providence, RI 02903
Phone: (401) 222-2678
Fax: (401) 222-2968
http://www.preservation.ri.gov/
South Carolina
State Historic Preservation Office
Department of Archives and History
8301 Parklane Road
Columbia, SC 29223
Phone; (803) 896-6178
Fax: (803) 896-6167
http://shpo.sc.gov/
South Dakota
State Historic Preservation Office
State Historical Society
900 Governors Drive
Pierre, SD 57501-2217
Phone: (605) 773-3458
Fax: (605) 773-6041
http://www.sdhistory.org/HP/histpres.htm
Tennessee
Tennessee Historical Commission
Department of Environment and Conservation
2941 Lebanon Road
Nashville, TN 37243-0442
Phone: (615) 532-1550
http://www.tn.gov/environment/history/
Texas
Texas Historical Commission
1511 Colorado
P.O. Box 12276
Austin, TX 78711-2276
Phone: (512) 463-6100
Fax: (512) 463-8222
http://www.thc.state.tx.us
Utah
Utah Division of State History
300 South Rio Grande Street
Salt Lake City, UT 84101
Phone: (801) 533-3500
Fax: (801) 533-3567
http://history.utah.gov/
Vermont
Division for Historic Preservation
National Life Building, 2nd Floor
Montpelier, VT 05620-1201
Phone: (802) 828-3213
Fax: (803) 828-3206
http://www.historicvermont.org/
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Virginia
Department of Historic Resources
2801 Kensington Avenue
Richmond, VA 23221
Phone: (804) 367-2323
http://www.dhr.virginia.gov/
Washington
Department of Archeology and Historic
Preservation
1063 South Capitol Way, Suite 106
Olympia, WA 98501
Phone: (360) 586-3065
http://www.dahp.wa.gov/
West Virginia
West Virginia Division of Culture and History
Historic Preservation Office
Cultural Center
1900 Kanawha Boulevard East
Charleston, WV 25305-0300
Phone: (304) 558-0220
Fax: (304) 558-2779
http://www.wvculture.org/
Wisconsin
Historic Preservation Division
State Historical Society of Wisconsin
816 State Street
Madison, WI 53706-1417
Phone: (608) 264-6493
http://www.wisconsinhistory.org/hp/
Wyoming
Wyoming State Historic Preservation Office
Barrett Building
2301 Central Avenue
3rd Floor
Cheyenne, WY 82002
Phone: (307) 777-7697
Fax: (307) 777-6421
http://wyoshpo.state.wy.us/
American Samoa
c/o Executive Offices of the Governor American
Samoa
Historic Preservation Office American Samoa
Government
Pago Pago, American Samoa 96799
Phone: (684) 699-2316
Fax: (684) 699-2276
http://ashpo.org/
Virgin Islands
State Historic Preservation Office
Nisky Center
17 Kongens Gade
St. Thomas, VI 00802
Phone: (340) 776-8605
Fax: (340) 776-7236
http://www.dpnr.gov.vi/historic.htm
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING F-1
Appendix F
Professional Organizations
The organizations listed below can provide information about registered design professionals and licensed con-
tractors in or near the area where you live.
American Institute of Architects (AIA)
1735 New York Avenue, NW
Washington, DC 20006-5292
Phone: (202) 626-7300 or (800) 242-3837
Fax: (202) 626-7547
http://www.aia.org
American Society of Civil Engineers (ASCE)
International Headquarters
1801 Alexander Bell Drive
Reston, VA 20191-4400
Phone: (703) 295-6300 or (800) 548-2723
Fax: (703) 295-6319
http://www.asce.org
Association of State Floodplain Managers (ASFPM)
2809 Fish Hatchery Road
Madison, WI 53713
Phone: (608) 274-0123
Fax: (608) 274-0696
http://www.floods.org
International Association of Structural Movers (IASM)
1223 Morning Shore Drive, Suite 200
P.O. Box 2637
Lexington, SC 29071
Phone: (803) 951-9304
Fax: (803) 951-9314
http://www.iasm.org
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Insurance Institute for Business and Home Safety (IBHS)
4775 E. Fowler Avenue
Tampa, FL 33617
Phone: (813) 286-3400
Fax: (813) 286-9960
http://www.disastersafety.org
International Code Council (ICC)
Headquarters
500 New Jersey Avenue, NW, 6th Floor
Washington, DC 20001-2070
Phone: (888) 422-7233
Fax: (202) 599-9871
http://www.iccsafe.org
National Association of Home Builders (NAHB)
1201 15th Street, NW
Washington, DC 20005
Phone: (202) 266-8200 or (800) 368-5242
Fax: (202) 266-8400
http://www.nahb.org
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-1
Appendix G
Retrofitting Checklist
Use this checklist when you follow the four steps described in this chapter. The information you record here will
help you work with local officials, design professionals, and contractors. Use the decision-making matrices that
follow this checklist to decide which retrofitting method is right for your home.
Step 1 – Determine the Hazards to Your Home
1. How long have you lived in your home?
___ years
2. Was your home ever flooded during that time?
___ yes ___ no
(If your answer is yes, go to question 3; if your answer is no, go to question 14.)
3. How many times has your home been flooded? ________
4. What were the dates of flooding?
Flood #1 ______________ Flood #4 ______________
Flood #2 ______________ Flood #5 ______________
Flood #3 ______________
For each flood, answer questions 5 through 13 as best you can.
G-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
G RETROFITTING CHECKLIST
5. To your knowledge, were frequencies assigned to any of the floods (e.g., 2-percent-annual-
chance flood, 1-percent-annual-chance flood)? If so, what were they?
Flood #1 _________________________________________________________________________
Flood #2 _________________________________________________________________________
Flood #3 _________________________________________________________________________
Flood #4 _________________________________________________________________________
Flood #5 _________________________________________________________________________
6. How high did the floodwaters rise in your home?
(If you can, state the height of the water above the lowest floor, including the basement floor.)
Flood #1 ______________ Flood #4 ______________
Flood #2 ______________ Flood #5 ______________
Flood #3 ______________
7. About how long did your home remain flooded?
(You can give your answer in days, weeks, or months, as appropriate.)
Flood #1 ______________ Flood #4 ______________
Flood #2 ______________ Flood #5 ______________
Flood #3 ______________
8. Did you have any warning before your home was flooded? If so, how much warning?
(You can give your answer in days or hours as appropriate.)
Flood #1 ___ No Warning ___ Warning _______ Days/Hours
Source of warning (news report, local officials, firsthand observation): _________________________
Flood #2 ___ No Warning ___ Warning _______ Days/Hours
Source of warning (news report, local officials, firsthand observation): _________________________
Flood #31 ___ No Warning ___ Warning _______ Days/Hours
Source of warning (news report, local officials, firsthand observation): _________________________
Flood #4 ___ No Warning ___ Warning _______ Days/Hours
Source of warning (news report, local officials, firsthand observation): _________________________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-3
RETROFITTING CHECKLIST G
Flood #5 ___ No Warning ___ Warning _______ Days/Hours
Source of warning (news report, local officials, firsthand observation): _________________________
9. Did the floodwaters cause scour and/or erosion around your home or elsewhere on your lot?
If so, describe the effects.
Flood #1 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred
Description _______________________________________________________________________
________________________________________________________________________________
Flood #2 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred
Description _______________________________________________________________________
________________________________________________________________________________
Flood #3 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred
Description _______________________________________________________________________
________________________________________________________________________________
Flood #4 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred
Description _______________________________________________________________________
________________________________________________________________________________
Flood #5 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred
Description _______________________________________________________________________
________________________________________________________________________________
10. Was your home damaged by wave action or the impact of ice or other floodborne debris?
If so, describe the damage.
Flood #1 ___ No Waves or Debris ___ Waves ___ Debris
Description of Damage ______________________________________________________________
________________________________________________________________________________
Flood #2 ___ No Waves or Debris ___ Waves ___ Debris
Description of Damage ______________________________________________________________
________________________________________________________________________________
G-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
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Flood #3 ___ No Waves or Debris ___ Waves ___ Debris
Description of Damage ______________________________________________________________
________________________________________________________________________________
Flood #4 ___ No Waves or Debris ___ Waves ___ Debris
Description of Damage ______________________________________________________________
________________________________________________________________________________
Flood #5 ___ No Waves or Debris ___ Waves ___ Debris
Description of Damage ______________________________________________________________
________________________________________________________________________________
11. How difficult and/or expensive was cleaning up after the floodwaters receded?
(If you can, describe what you had to do to clean up both inside your home and around your lot,
how long the cleanup took, and how much you spent on cleanup.)
Flood #1 Cleanup Description ______________________________________________________
________________________________________________________________________________
Cost $ _______________ Time _______________
Flood #2 Cleanup Description ______________________________________________________
________________________________________________________________________________
Cost $ _______________ Time _______________
Flood #3 Cleanup Description ______________________________________________________
________________________________________________________________________________
Cost $ _______________ Time _______________
Flood #4 Cleanup Description ______________________________________________________
________________________________________________________________________________
Cost $ _______________ Time _______________
Flood #5 Cleanup Description ______________________________________________________
________________________________________________________________________________
Cost $ _______________ Time _______________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-5
RETROFITTING CHECKLIST G
12. What was the total cost to repair all flood damage, not including the cleanup costs listed
above?
Flood #1 $______________ Flood #4 $______________
Flood #2 $______________ Flood #5 $______________
Flood #3 $______________
13. What was the total value of all home contents (furnishings, belongings, etc.) damaged by
flooding?
Flood #1 $______________ Flood #4 $______________
Flood #2 $______________ Flood #5 $______________
Flood #3 $______________
14. Is your home either in or near one of the shaded areas on the wind hazard map in Figure 4-1?
If you are not sure how to interpret Figure 4-1, your local officials and design professional can help
you.
___ yes ____ no
15. Has your home ever been damaged by a hurricane or other high-wind event?
___ yes ___ no.
If your answer is yes, note how many times and describe both the damage and the repairs made.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
16. Is your home either in or near one of the shaded areas on the earthquake hazard map in
Figure 4-2? If you are not sure how to interpret Figure 4-2, your local officials and design professional
can help you.
___ yes ___ no
G-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
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17. Has your home ever been damaged by an earthquake?
___ yes ___ no.
If your answer is yes, note how many times and describe both the damage and the
repairs made.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
18. Has your home ever been damaged by other hazard events, such as fires or landslides?
___ yes ___ no.
If your answer is yes, note how many times and describe both the damage and the repairs made.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-7
RETROFITTING CHECKLIST G
Step 2 – Inspect Your Home
Provide as much of the following information as you can about your home.
1. When was your home built? _____
2. Construction type (see Section 3.2.1; check all that apply):
___ frame ___ masonry veneer ___ masonry ___ manufactured home
3. Foundation type (see Section 3.2.2; check all that apply):
___ basement (subgrade on all sides) ___ walkout-on-grade basement ___ crawlspace
___ slab-on-grade ___ piers ___ posts/columns ___ piles
4. Describe any other damage and repairs or other additions to your home other than those you
described in Step 1. Other damages would include foundation settlement, dry rot, and termite
damage.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
To answer questions 5 through 9, you will need to have at least a rough idea of the DFE for your ret-
rofitting project. If you don’t have enough information to answer these questions now, go to Step 3
and determine your DFE when you talk with your local official(s).
5. Approximate difference between elevation of lowest floor (including basement) and design
flood elevation (DFE) (see Figure 4-3):
___ feet
6. Interior utilities below the DFE (check all that apply):
___ furnace ___ ductwork ___ hot water heate ___ electrical panel ___ electrical outlets
___ electrical switches ___ baseboard heaters ___ sump pumps ___ fuel tanks
other ____________________________________________________________________________
G-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
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7. Exterior utilities below the DFE (check all that apply):
___ air conditioning / heat pump compressor ___ electric meter ___ fuel tank
___ septic tank ___ well ___ gas meter
other_____________________________________________________________________________
8. Major appliances below the DFE (check all that apply):
___ washer ___ dryer ___ refrigerator ___ freezer
other ____________________________________________________________________________
9. How many drains (such as sink, tub, and floor drains) and toilets are below the DFE? _______
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-9
RETROFITTING CHECKLIST G
Step 3 – Check with Your Local Officials
When you meet with your local official(s), be sure to discuss the issues below. Also, make note of the
information you receive from the local officials. (You may find that you will need to talk with more
than one person to get all the information you need.)
1. Explain your retrofitting needs, go over the information you recorded in Steps 1 and 2, and discuss any
preferences you may have regarding the retrofitting methods described in Chapter 3.
2. Provide the official with photographs of your home and a copy of a plat map that shows the dimensions
of your lot and the location of your home. If you do not have a plat map, ask how you can get one.
3. Ask whether your home is in the regulatory floodplain. If the answer is yes, ask what the BFE is at your
home and whether your home is in the floodway or Coastal High Hazard Area (Zone V). Ask whether
any restudies or revisions are underway that might provide updated flood hazard information for the area
where your home is located. Also, ask for additional flood hazard information concerning characteristics
such as flow velocity, the potential for wave action and debris flow, rates of rise and fall, warning time,
and duration of inundation. This additional information may be useful to your design professional.
4. Ask whether your home is subject to your community’s regulatory requirements concerning Substantially
Damaged structures or whether the retrofitting measure you are considering would subject your home to
Substantial Improvement requirements. (See the definitions of Substantial Improvement and Substantial
Damage in Section 2.5 and Section 3.1.1)
5. Ask whether your home is subject to high winds, earthquakes, and other hazards, such as wildfires.
Refer to the maps in Figures 4-1 and 4-2.
6. Ask whether your State and/or community enforces building codes or other regulations that could affect
your retrofitting decision, including any floodplain management regulations more stringent than those
required by the NFIP. For example, ask whether the State or community requires freeboard for flood
protection measures.
7. In your discussion of building codes, ask whether retrofitting will require that you upgrade other compo-
nents of your home (such as electrical and plumbing systems) to meet current code requirements.
8. Ask about the types of permits and fees that may be required in connection with the retrofitting methods
you are considering.
9. Ask whether the official is aware of any Federal, State, or local historic preservation regulations that may
affect your property. If necessary, have the official follow up with the SHPO (see Appendix E) to be sure
that your retrofitting project is in compliance with all preservation laws.
10. Ask about Federal, State, and local programs that provide financial assistance for certain types of home-
owner flood protection retrofitting projects. Ask whether you are eligible for assistance.
11. Go through the appropriate decision-making matrix (see Section 4.2) with the official and discuss any
questions you may have about the advantages and disadvantages of the alternative retrofitting methods.
12. Ask for any guidance that local officials can provide to help you find a good contractor or design
professional.
G-10 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING
G RETROFITTING CHECKLIST
Step 4 – Consult a Design Professional and Retrofitting Contractor
Initial Meeting
1. Explain your retrofitting needs; go over the information you recorded in Steps 1 and 2; discuss the
results of your meeting with your local official(s), including the decision-making matrix; and discuss
any preferences you may have regarding retrofitting methods you selected in
Step 3.
2. Verify that the design professional is licensed and registered in the State where the work will be done.
3. Verify that the contractor is licensed, bonded, and insured as required by State and local laws.
4. Ask for references and proof of proper bonds and insurance, including disability and workers’
compensation.
5. Decide whether you, the design professional, or the contractor will be responsible for obtaining
and managing the work of subcontractors and for obtaining all permits required by State and local
agencies.
6. Schedule a site visit.
Site Visit
1. Ask the design professional or contractor to tell you about any characteristics of your home or lot that
would affect your selection of a retrofitting method.
2. Once you decide on a retrofitting method, ask for a written estimate of the project cost and schedule.
Contract
1. If you are satisfied with the cost estimate and schedule, get a written, signed, and dated contract that
describes the work to be done and that states the estimated cost, the payment schedule, and the start
and completion dates of the work.
2. Ask whether the contractor will provide a warranty or guarantee for the work performed. Any warranty
or guarantee should be written into the contract. The contract should state the terms of the warranty or
guarantee, who is responsible for honoring it, and how long it will remain valid.
Notes
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FEMA P-321
Catalog No. 08322-1
FEMA
U. S. D E PARTMEN
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U. S. D E PARTMEN
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U. S. D E PARTMEN
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