Evaluation of the 
National Flood Insurance Programs 
Building Standards 
Christopher P. Jones, William L. Coulbourne, 
Jamie Marshall, and Spencer M. Rogers, Jr. 
Christopher Jones and Associates 
October 2006 
Prepared under subcontract to the American Institutes for Research 
as part of the 20012006 Evaluation of the National Flood Insurance Program
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 Evaluation of the 
National Flood Insurance Programs 
Building Standards 
Prepared as part of the 2001-2006 
Evaluation of the National Flood Insurance Program 
Christopher P. Jones, William L. Coulbourne, 
Jamie Marshall, and Spencer M. Rogers, Jr. 
Christopher Jones and Associates 
5525 Jomali Drive 
Durham, NC 27705 
September 2006 
REPORTS IN THE EVALUATION OF THE NATIONAL FLOOD 
INSURANCE PROGRAM 
This Evaluation consists of a series of reports assessing questions identified and prioritized by a 
steering committee about the National Flood Insurance Program. The reports of the Evaluation 
will be posted on the FEMA website as they are finalized. The website URL is 
http://www.fema.gov/business/nfip/nfipeval.shtm. The reports in the Evaluation are: 
The Evaluation of the National Flood Insurance Program  Final Report 
American Institutes for Research and NFIP Evaluation Working Group 
Assessing the Adequacy of the National Flood 
Insurance Program's 1 Percent Flood Standard. 
Galloway, Baecher, Plasencia, Coulton, 
Louthain, Bagha, and Levy, Water Policy 
Collaborative, University of Maryland. 
Assessing the National Flood Insurance 
Programs Actuarial Soundness. Bingham, 
Charron, Kirschner, Messick and Sabade, 
Deloitte Consulting. 
Costs and Consequences of Flooding and 
the Impact of the National Flood Insurance 
Program. Sarmiento and Miller, Pacific 
Institute of Research and Evaluation. 
Developmental and Environmental Impacts of 
the National Flood Insurance Program: A 
Review of Literature. Rosenbaum, University of 
Florida. 
The Developmental and Environmental Impact 
of the National Flood Insurance Program: A 
Summary Research Report. Rosenbaum and 
Bouleware, University of Florida. 
An Evaluation of Compliance with the National 
Flood Insurance Program Part A: Achieving 
Community Compliance. Monday, Grill, 
Esformes, Eng, Kinney and Shapiro, American 
Institutes for Research. 
An Evaluation of Compliance with the National 
Flood Insurance Program Part B: 
Are Minimum Building Requirements Being 
Met? Mathis and Nicholson, Dewberry. 
Evaluation of the National Flood Insurance 
Programs Building Standards. Jones, 
Coulbourne, Marshall, and Rogers, Christopher 
Jones and Associates. 
Managing Future Development Conditions in 
the National Flood Insurance Program. Blais, 
Nguyen, Tate, Dogan, ABSG Consulting; and 
Mifflin and Jones. 
The National Flood Insurance Programs 
Environmental Reviews: An Assessment of 
FEMAs Implementation of NEPA and Executive 
Order 11988. Rosenbaum, University of Florida. 
The National Flood Insurance Programs 
Mandatory Purchase Requirement: Policies, 
Processes and Stakeholders. Tobin and Calfee, 
American Institutes for Research. 
The National Flood Insurance Programs 
Market Penetration Rate: Estimates and Policy 
Implications. Dixon, Clancy, Seabury, and 
Overton, RAND Corporation. 
Performance Assessment and Evaluation 
Measures for Periodic Use by the National 
Flood Insurance Program. Miller, Langston, 
and Nelkin, Pacific Institute of Research and 
Evaluation. 
State Roles and Responsibilities in the National 
Flood Insurance Program. Mittler, Morgan, 
Shapiro, and Grill, American Institutes for 
Research. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
The research described in this report was funded with Federal funds from the Federal Emergency 
Management Agency under contract # 282-98-0029 and under subcontract to the American 
Institutes for Research. The content of this publication does not necessarily reflect the views or 
policies of the Federal Emergency Management Agency, nor does mention of trade names, 
commercial products, or organizations imply endorsement by the U.S. Government. 
Established in 1946, with headquarters in Washington, D.C., the American Institutes for 
Research (AIR) is an independent, nonpartisan not-for-profit organization that conducts 
behavioral and social science research on important social issues and delivers technical 
assistance both domestically and internationally in the areas of health, education, and workforce 
productivity. 
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BIOGRAPHICAL INFORMATION ON REPORT AUTHORS 
Christopher P. Jones is a professional engineer specializing in the characterization of flood 
loads and conditions, and how they affect buildings and structures. He is a recognized expert on 
floodplain mapping and building codes and standards. Mr. Jones serves as Chairman of the 
ASCE-7 Flood Loads Task Committee. He is Chairman of the ASCE-24 Standards Committee 
for Flood Resistant Design and Construction. He is currently serving as president of the Applied 
Technology Council. Mr. Jones was one of the principal authors on the rewrite of FEMAs 
Coastal Construction Manual and on FEMAs Home Builders Guide to Coastal Construction. 
He has served as a member of FEMAs Building Performance Assessment Teams or Mitigation 
Assessment Teams for hurricanes Opal, Fran, Ivan and Katrina. 
William L. Coulbourne is a principal structural engineer and department head at URS 
Corporation in Gaithersburg, Maryland. He has 37 years of experience as an engineer and 
manager. His expertise includes building design, methods, materials, and codes. He is 
experienced in hazard-related design and construction of wind- and hurricane-resistant 
structures. He served as program manager for FEMAs Mitigation Assessment Teams for 
hurricanes Charley and Ivan, and served as a member of FEMAs Building Performance 
Assessment Team for the New York City World Trade Center disaster. He teaches courses for 
FEMA on flood resistant design and coastal construction issues. He is a member of the ASCE 
standards committees for ASCE 7 (Minimum Design Loads for Buildings and Other Structures) 
and ASCE 24 (Flood Resistant Design and Construction). He has performed more than 1,200 
structural inspections and designed more than 100 repairs for structural failures. 
Jamie Marshall is a structural engineer for URS Corporation. She has a Bachelors Degree in 
Architectural Engineering with an emphasis in structures. Ms. Marshalls expertise includes 
structural analysis and design, facilities evaluation and inspection, and post-disaster assessments 
and cost estimates. 
Spencer M. Rogers, Jr. joined North Carolina Sea Grant in 1978 as an extension specialist in 
hurricane-resistant construction techniques, shoreline erosion, coastal management and marine 
construction. His faculty affiliations are with the University of North Carolina at Wilmingtons 
Center for Marine Science and as an adjunct with the North Carolina State Universitys 
Department of Civil Engineering. He was previously employed by Florida Bureau of Beaches 
and Shores. His education includes a BS in Engineering from the University of Virginia in 1973 
and a MS in Coastal and Oceanographic Engineering from the University of Florida in 1975. 
His recent work includes participation in FEMAs Hurricane Katrina Mitigation Assessment 
Team. 

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TABLE OF CONTENTS 
EXECUTIVE SUMMARY .................................................................................VII 
1. BACKGROUND ..................................................................................................1 
1.1. Purpose of the Study .......................................................................................................... 1 
1.1.1. Basic Questions to be Addressed................................................................................. 2 
1.2. NFIP Flood Hazard Zones and Building Standards........................................................... 2 
1.2.1. All Zones within the SFHA ......................................................................................... 2 
1.2.2. V Zones........................................................................................................................ 3 
1.2.3. A Zones........................................................................................................................ 4 
1.2.4. Coastal A Zones........................................................................................................... 5 
2. STUDY METHODOLOGY................................................................................7 
3. LITERATURE REVIEW ...................................................................................9 
3.1. Building Performance ........................................................................................................ 9 
3.1.1. Flood Insurance Incentives for Sound Building Practices........................................... 9 
3.2. Building Foundations and Construction Costs ................................................................ 10 
4. DEFINING TYPICAL BUILDINGS AND FLOOD CONDITIONS FOR 
THIS STUDY..........................................................................................................15 
4.1. Buildings Evaluated in this Study.................................................................................... 15 
4.2. Flood and Wind Conditions Evaluated in this Study....................................................... 17 
4.2.1. V Zone ....................................................................................................................... 20 
4.2.2. Coastal A Zone .......................................................................................................... 20 
4.2.3. A Zone ....................................................................................................................... 21 
5. FOUNDATION DESIGNS................................................................................23 
5.1. Pile Foundations............................................................................................................... 23 
5.1.1. Pile Design Review.................................................................................................... 24 
5.2. Masonry Pier Foundations ............................................................................................... 27 
5.3. Wall Foundations............................................................................................................. 27 
5.4. Elevation on Fill (Concrete Slabs)................................................................................... 27 
6. BUILDING COSTS ...........................................................................................29 
6.1. A Note about Building Costs and This Study.................................................................. 29 
6.2. Building Cost Calculation Procedure............................................................................... 29 
6.2.1. Key Cost Definitions.................................................................................................. 29 
6.2.2. Construction Quality.................................................................................................. 30 
6.3. Foundation Costs and Final Building Costs .................................................................... 34 
6.3.1. Pile Foundations......................................................................................................... 34 
6.3.2. Masonry Pier Foundations ......................................................................................... 37 
6.3.3. Wall Foundations....................................................................................................... 41 
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6.3.4. Elevation on Fill (Concrete Slab) .............................................................................. 42 
6.4. Freeboard and Foundation Cost Comparison...46 
6.4.1. Pile Foundation Cost.................................................................................................. 46 
6.4.2. Pier Foundation Cost.................................................................................................. 46 
6.4.3. Wall Foundation Cost ................................................................................................ 47 
6.4.4. Slab on Fill Foundation Cost ..................................................................................... 47 
6.4.5. Foundation Cost Comparison .................................................................................... 47 
7. BENEFIT-COST ANALYSES .........................................................................49 
7.1. Benefit-Cost Model Description ...................................................................................... 50 
7.2. Model Inputs Used in this Study...................................................................................... 50 
7.2.1. Discount Rate............................................................................................................. 52 
7.2.2. Mitigation Project Description................................................................................... 54 
7.2.3. Useful Life ................................................................................................................. 54 
7.2.4. Building Damage that Results in Demolition ............................................................ 54 
7.2.5. Contents Value........................................................................................................... 54 
7.2.6. Public/Non-Profit Use of the Buildings..................................................................... 54 
7.2.7. Lost Rent and Business Income................................................................................. 54 
7.2.8. Displacement Time and Costs ................................................................................... 54 
7.2.9. Flood Elevation Data ................................................................................................. 55 
7.2.10. Flood Depth-Damage Functions .............................................................................. 57 
7.3. B/C Results ...................................................................................................................... 60 
7.3.1. V Zones and Coastal A Zones ................................................................................... 60 
7.3.2. A Zones...................................................................................................................... 68 
7.3.3. Sensitivity of B/C Results to Displacement Costs..80 
7.3.4. Effects of Flood Insurance Premium Savings Due to Freeboard............................... 80 
8. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS...................85 
8.1. Study Intent and Overview .............................................................................................. 85 
8.2. Study Findings ................................................................................................................. 86 
8.3. NFIP Building Standards: Effectiveness and Costs......................................................... 89 
8.4. Do NFIP Building Standards Minimize Losses, Now and in the Future? ....................... 90 
8.5. NFIP Building Standards and Protection During the 100-Year Flood ............................ 91 
8.6. Recommendations............................................................................................................ 91 
9. ACRONYMS......................................................................................................95 
10. REFERENCES.................................................................................................97 
Appendix 1: NFIP Building Standards Survey........................................................................... 101 
Appendix 2: A Comparative Cost Evaluation of Foundation Types Permitted by NFIP 
Regulations in Coastal A and V Zones .................................................................. 107 

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Appendix 3: An Approximate Method for Estimating Flood Depths for Various Recurrence 
Intervals.................................................................................................................. 113 

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ACKNOWLEDGEMENTS 
The authors are indebted to the staff of FEMA and AIR for their ongoing assistance, guidance 
and comments during this study. 
The authors would also like to thank five other individuals who contributed greatly to the studys 
technical strength and veracity: 
Robert Bruce, member of the studys expert review panel; structural engineer, Wiss 
Janney Elstner Associates, Emeryville, CA 
David Divoky, who provided assistance with flood frequency statistics; Watershed 
Concepts, Atlanta, GA 
Doug Plasencia, member of the studys expert review panel; assistant vice president and 
water resources engineer, Michael Baker Jr., Phoenix, AZ 
Michael Powell, member of the studys expert review panel; NFIP State Coordinator, 
Delaware Department of Soil and Water Conservation, Dover, DE 
Wilbert Thomas, who provided a methodology for generalizing riverine flood depth 
frequency calculations; senior water resources engineer, Michael Baker Jr., 
Alexandria, VA 

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EXECUTIVE SUMMARY 
Background and Purpose of this Study 
Floodplain management regulations adopted by communities and states contain 
provisions that affect new construction in floodplain areas. These regulations must equal or 
exceed National Flood Insurance Program (NFIP) minimum design and construction 
requirements for buildings in the Special Flood Hazard Area (SFHA), and are intended to 
minimize flood damage to buildings during the base flood (also known as the 100-year flood, 
and as the 1-percent annual chance flood). 
The purpose of this study was to evaluate those design and construction requirements, 
with particular emphasis on: 1) damages prevented or induced by strict adherence to those 
minimum requirements, and 2) the costs and benefits of modifying the minimum requirements to 
reduce building damages during flooding. 
Specifically, this study was designed and conducted to address three sets of questions 
regarding NFIP building standards for typical single family homes in the SFHA: 
 What impacts have the NFIPs building standards for new construction in Special 
Flood Hazard Areas had on risk exposure and property loss? Which standards are 
the most and least effective in reducing exposure and property losses due to 
floods? Is the cost of implementing the major standards commensurate with their 
benefits? 
 Are the NFIPs standards for construction and building design adequate and 
sufficiently stringent so that losses are minimized at a reasonable cost to 
communities and property owners when flood damage occurs? Are the standards 
and incentives sufficient to protect against flood risks that may be increasing in 
the future? 
 Do the NFIPs building standards effectively protect buildings from damages 
during the 100-year flood? If current standards are not effective, how should 
FEMA change them? Are higher levels of protection achievable and more 
important, are the benefits achieved by these standards commensurate with the 
costs associated with meeting them? 
These issues were addressed through a study that included the following: 
 Review of building flood damage and foundation performance in coastal and noncoastal 
floodplains. 
 Review of the literature and calculation of construction costs for one-and twostory 
houses with several foundation types under a variety of flood conditions. 
 Calculation of the costs of adding freeboard and changing foundations. FEMAs 
benefit-cost analysis (BCA) model was modified in this study to allow 
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generalized benefit/cost calculations to be made with all cost inputs expressed as a 
percentage of the initial (at-BFE) building cost. The model was run with variable 
discount rates (ranging from 3% to 9%), flood damage functions (V and Coastal 
A, and A), BFEs (in coastal areas, ranging from 12 ft to 20 ft mean sea level 
[msl]) and Flood Hazard Factors (FHF) in riverine areas, ranging from 25 to 150. 
 The B/C models run in this study account for building and contents damages, and 
do not account for other economic costs to the building owner or community (e.g., 
clean-up and demolition costs, uninsured losses, displacement and relocation 
costs, loss of jobs and tax base, etc.). The resulting benefit-cost ratios (B/C) are 
conservative, and will understate the true benefits associated with exceeding 
minimum NFIP building standards. 
 Calculation of the maximum justified cost of mitigation, i.e., freeboard and/or 
foundation changes at the time of initial construction -- expressed as a percentage 
of initial construction cost -- that would yield a B/C greater than or equal to 1.0. 
All cost inputs were expressed as a percentage of the initial (at-BFE) construction 
cost to generalize the results. 
 Examination of the sensitivity of the B/C results to inclusion of displacement 
costs when building occupants must move out of flood damaged homes. 
 Examination of flood insurance premium discounts for adding freeboard, and 
development of a general method to determine the time to recover the costs of 
freeboard through future flood insurance premium savings. 
General Findings 
On an individual building level, NFIP building standards have reduced flood damage 
relative to nearby pre-FIRM type structures. Flood losses for new construction are reduced 
through elevation and proper selection of the building foundation. Post-storm observations and 
calculations made during this study demonstrate that incorporation of freeboard is one of the 
most effective means of reducing property losses. 
Generally speaking, NFIP building standards do reduce flood losses to new construction 
under present day base flood events. However, building standards are implemented in 
conjunction with the Flood Insurance Rate Map (FIRM), which does not account for increasing 
flood hazards in the future. Thus, while NFIP building standards may be generally effective 
today, their future effectiveness will be reduced as the FIRM becomes obsolete due to changing 
flood conditions. Revising building standards may be one way to compensate for changing flood 
conditions in the future. 
This study found, for the residential buildings analyzed, the cost of adding freeboard or 
installing a more flood-resistant foundation at the time of construction is modest but the benefit 
of doing so can be great, particularly in coastal areas subject to wave effects and riverine 
floodplains with small flood hazard factors. Incorporating freeboard and/or changing the 
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foundation type would also help to reduce future flood damage resulting from sea level rise and 
erosion in coastal areas, and from development impacts in riverine areas. 
Under the current flood premium rate structure, flood premium discounts will be 
sufficient to recover the incremental costs borne by property owners to incorporate freeboard at 
the time of initial construction -- in just a few years time for many buildings. 
However, floods more severe than the 100-year flood do occur, and incorporation of 
freeboard and modified foundations can help reduce losses from such floods. This study 
indicates that higher levels of protection are achievable for single family structures, and that the 
benefits of doing so will exceed the costs, particularly in high hazard areas. Additional B/C 
analyses could help to define a flood return period for which additional elevation is justified for 
other classes of structures. 
With a few exceptions, NFIP building standards evaluated by this study generally protect 
against the 100-year flood. NFIP flood insurance premium rates generally promote sound 
construction practices and reduce potential flood damages. However, some changes to building 
standards and insurance premium rates are warranted, as a way of further reducing flood 
damages, providing additional incentives for flood loss reduction, and eliminating disincentives. 
While this study did not investigate building practice effects on flood loss reduction at a 
community level, extension of the individual building findings to a broader scale seems 
reasonable. Reduced flood damage to individual buildings aggregates to reduced flood losses and 
disruption to the community. Study authors have observed this first-hand as part of post flood 
investigations -- where flood damage was widespread and great, individuals and communities 
often struggle to recover, while other nearby communities with less flood damage recover 
quickly. 
This study did not investigate the effects of potential changes in NFIP building standards 
on the flood insurance fund, disaster assistance payments and other financial aspects of the NFIP 
and FEMA. However, since modified building standards could reduce flood damage at the 
individual building level, it seems reasonable to expect flood claims, disaster assistance and 
other post-disaster payments might also be reduced. The exact impact on the NFIP would depend 
on flood premiums received and payments made. The study authors believe that the cost of 
implementing building standards changes would be small, since the NFIP and the participating 
communities already enforce standards which are similar to the changed standards this study 
recommends. 
Detailed Findings 
At the time of initial construction, the incremental costs of replacing minimally compliant 
A zone foundations (such as slab-on-fill and crawlspace foundations) with pier foundations or 
pile foundations are relatively small, generally less than 5% to 10% of the cost of the building. 
In Coastal A zones, post-storm field studies have shown that minimally compliant A zone 
foundations often fail, and this replacement is warranted. In A zones outside coastal areas, NFIP 
compliant slab-on-fill and crawlspace foundations are generally adequate, and the incremental 
cost of changing to a pile foundation is not likely justified (but owners may wish to do so to 
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create under-house parking). However, changing to a pier foundation is probably justified, 
especially for flood depths more than a few feet above grade. 
At the time of initial construction, the cost of incorporating freeboard in a pile or masonry 
pier foundation averages approximately 1% to 2% of the at-BFE building cost for 4 ft of added 
freeboard (approximately 0.25% to 0.5% per foot of freeboard). 
At the time of initial construction, the cost of incorporating freeboard in a masonry wall 
with interior pier (crawlspace) foundation averages approximately 3% to 6% of the at-BFE 
building cost for 4 ft of added freeboard (approximately 0.8% to 1.5% per foot of freeboard). 
At the time of initial construction, the cost of incorporating freeboard in a fill foundation 
averages approximately 3% to 11% of the at-BFE building cost for 4 ft of added freeboard. 
Although the fill quantity and fill cost do not increase linearly with freeboard, they add an 
average of 0.8% to 3.0 % per foot of freeboard to the at-BFE building cost. 
As expected, the B/C ratios calculated in this study decrease with increasing discount 
rate, with all other factors held constant. B/C ratios also decrease with increasing BFE and FHF, 
indicating that a foot of freeboard is worth less (in terms of damage reduction) in areas where 
there is a greater vertical spread in flood elevations associated with different return periods. 
B/C calculations were tabulated and the B/Cs were determined for various combinations 
of freeboard, additional construction cost and discount rate. The data were then examined to 
identify the percent of additional construction cost that an owner would be justified in spending 
at the time of construction (B/C = 1.0) for each freeboard-BFE-discount rate or freeboard-FHFdiscount 
rate combination. 
In the V zone and Coastal A zone cases studied, calculations show that it is worth 
spending from 103% to 106% of the at-BFE building cost to add one to four feet of freeboard, 
and in some cases it may be worth spending up to 107% to 114% of the at-BFE building cost. 
In the A zone cases studied, calculations show that it is worth spending less than in V 
zones and Coastal A zones to add freeboard  this is due to the fact that A zone flood depthdamage 
functions predict less damage for a given flood depth than do the V zone/Coastal A zone 
functions. The A zone calculations show it is worth spending from 100.5% to 102% of the at- 
BFE building cost to add one to four feet of freeboard, and in some cases it may be worth 
spending up to 103% to 106% of the at-BFE building cost. 
A sensitivity analysis was undertaken to investigate the effect of including displacement 
costs in the B/C calculations. Using BCA default displacement times, the effect varies slightly 
between flood hazard zones and with number of stories in an A zone. However, the effect can be 
generalized as follows: adding monthly displacement costs equal to 1% of the initial (at-BFE) 
building cost increases the computed B/C by approximately 10%, and so forth. 
The relationship between initial freeboard costs and flood premium discounts was also 
considered in a separate analysis. Even if future building and contents damages prevented are not 
considered the annual flood premium savings are generally sufficient to pay for the costs of 
adding freeboard in several years time for many buildings. In the case of V zone buildings, the 
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time required to recover freeboard costs through flood premium savings is short  a year or two. 
In the case of A zone buildings, the recovery time can extend to more than 15 years, due to the 
lower A zone premiums and premium discounts, which are used to offset the initial freeboard 
cost. 
Recommendations 
B-1. The NFIP should not allow new A zone construction to be built with the top of the 
lowest floor at the BFE. Instead, the NFIP should require the top of the lowest floor of 
A zone structures to be built above the BFE such that the floor system is not in contact 
with flood waters during the base flood. This could be accomplished by either: 1) 
requiring sufficient freeboard, or 2) by changing the lowest floor reference elevation in 
A zones to be consistent with V zones (i.e., the bottom of the lowest horizontal 
structural member supporting the lowest floor must be at or above the BFE). 
B-2. The NFIP should require at least 1 foot of freeboard for all new construction in the 
special flood hazard area. The exact freeboard amount should be guided by several 
factors: 
 Freeboard requirements contained in consensus standards such as the American 
Society of Civil Engineers (ASCE) standard ASCE 24. ASCE 24 contains freeboard 
provisions which vary by building importance (the standard requires critical 
facilities to be elevated higher above the BFE than typical residential structures, for 
example). The ASCE 24 freeboard provisions apply to the lowest floor, the use of 
flood resistant materials and utilities. 
 Future flood conditions. ASCE 24 does not account explicitly for future increases in 
flood hazards, thus, freeboard in excess of ASCE 24 requirements may be 
appropriate in some flood hazard areas. The NFIP should consider flood loss 
reduction under present day base flood conditions and under future flood conditions 
when it establishes freeboard requirements. 
 Flood elevation frequency. The NFIP should attempt to establish freeboard 
requirements that are flood-risk consistent. For example, 1 foot of freeboard at a site 
with a flood hazard factor of 20 may yield protection against a certain flood return 
period event. Equivalent protection at a different site with a flood hazard factor of 
75 would require more than 1 foot of freeboard. 
B-3. The NFIP should mandate V zone design and construction practices in Coastal A zones 
(e.g., requiring open foundations and the area below the BFE to be free of obstructions, 
making the lowest floor reference elevation the bottom of the lowest horizontal 
structural member supporting the lowest floor, designing for simultaneous action of 
flood and wind). Some communities have mandated V zone standards in A zones for 
years, but implementation of this recommendation on a larger scale would require 
changes to the flood hazard mapping process and the FIRM. Note that the 2005 edition 
of ASCE 24 requires new construction in Coastal A zones to meet V zone standards, 
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and the FEMA has published supporting post-Katrina Coastal A zone construction 
guidance. 
B-4. The B/C results of this study are sensitive to the flood depth-damage function used in 
the analysis. The NFIP should, on an ongoing basis, review and update depth-damage 
functions based on flood claims data, results of Mitigation Assessment Team (MAT) 
investigations and other data. This may require collection of some additional data now 
deemed optional during the flood claims adjustment process. 
B-5. Flood insurance premium rates should reflect anticipated flood damages and provide 
incentives to property owners and communities to exceed minimum NFIP building 
standards. The Community Rating System (CRS) does this on a community scale, but 
additional effort is needed to provide incentives to individuals. For example: 
 The NFIP should re-evaluate flood insurance premium discounts for buildings in 
A zones. Current A zone discounts effectively cease at one to two feet above the 
BFE (unlike V zones where substantial discounts are awarded for up to four feet 
of freeboard). Additional discounts for increased freeboard in A zones may be one 
of the most powerful arguments for better construction that can be made to 
property owners. 
 The NFIP should revise flood premium rates and coverage for NFIP-compliant 
pile-elevated buildings outside the V zone. Present rates and coverage penalize 
property owners who might otherwise adopt the superior pole-type construction, 
with pilings extending above the lowest floor to a higher floor or the roof. 
B-6. The NFIP should consider development of an A Zone Risk Factor Rating Form and 
process, similar to that in place for V zones. This action could provide another way to 
reward A zone building owners to adopt design and construction practices that exceed 
NFIP minimum standards. 

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1. BACKGROUND 
The National Flood Insurance Program (NFIP) is a Federal program enabling property 
owners in participating communities to purchase insurance protection against losses from 
flooding. This insurance is designed to provide an insurance alternative to disaster assistance to 
meet the escalating costs of repairing damage to buildings and their contents caused by floods. 
The NFIP was created in 1968 to reduce flood risk and losses associated with flooding. Since its 
inception, the Program as been revised by Congress four times: 1973, 1997, 1994 and 2004. The 
NFIP is administered by the Mitigation Division of the Federal Emergency Management Agency 
(FEMA), which is part of the U.S. Department of Homeland Security. 
The NFIP has four primary goals: 
 To reduce the costs of flooding to individuals through the purchase of flood 
insurance. 
 To reduce future flood damages through the adoption of floodplain management 
regulations by communities and states. 
 To reduce federal expenditures associated with flood control and flood disaster 
assistance payments. 
 To restore and preserve the natural and beneficial values of floodplains. 
1.1. Purpose of the Study 
This study is part of the larger NFIP Evaluation, a series of studies assessing questions 
identified and prioritized by a steering committee about the National Flood Insurance Program. 
A list of all of the NFIP Evaluation studies is at the front of this report. This study focuses on 
NFIP design and construction standards for new buildings in the Special Flood Hazard Area 
(SFHA)1. 
Floodplain management regulations adopted by communities and states contain 
provisions that affect new construction in floodplain areas. These regulations must equal or 
exceed NFIP minimum design and construction requirements for buildings in the SFHA, which 
are contained in the Code of Federal Regulations (CFR), Title 44, Part 60  Criteria for Land 
Management and Use (U.S. Government Printing Office 2005). These requirements are intended 
to minimize flood damage to buildings during the base flood (also known as the 100-year flood, 
and as the 1-percent annual chance flood). 
The purpose of this study is to evaluate those design and construction requirements2, with 
particular emphasis on: 1) damages prevented or induced by strict adherence to those minimum 
requirements, and 2) the costs and benefits of modifying the minimum requirements to reduce 
building damages during flooding. 
1 The SFHA is the land within a community with a 1 percent, or greater, chance of flooding in any given year. This 
area is referred to by many as the 100-year floodplain. 
2 The term building standards will be used to refer to the NFIPs minimum design and construction requirements 
for new and substantially improved buildings in the SFHA. 
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1.1.1. Basic Questions to be Addressed 
The study was designed with the following questions (developed by FEMA and the 
American Institutes for Research [AIR]) in mind: 
 What impacts have the NFIPs building standards for new construction in Special 
Flood Hazard Areas (SFHA) had on risk exposure and property loss? Which 
standards are the most and least effective in reducing exposure and property 
losses due to floods? Is the cost of implementing the major standards 
commensurate with their benefits? 
 Are the NFIPs standards for construction and building design adequate and 
sufficiently stringent so that losses are minimized at a reasonable cost to 
communities and property owners when flood damage occurs? Are the standards 
and incentives sufficient to protect against flood risks that may be increasing in 
the future? 
 Do the NFIPs building standards effectively protect buildings from damages 
during the 100-year flood? If current standards are not effective, how should 
FEMA change them? Are higher levels of protection achievable and more 
important, are the benefits achieved by these standards commensurate with the 
costs associated with meeting them? 
1.2. NFIP Flood Hazard Zones and Building Standards 
In an attempt to address the basic questions listed above, this study divides the SFHA into 
three flood hazard zones (V zone, A zone, and Coastal A zone), and deals with building 
standards for each zone. However, there are certain building standards that apply to all new 
buildings in all parts of the SFHA. These are listed first, followed by the additional building 
standards pertinent to each flood hazard zone. 
1.2.1. All Zones within the SFHA 
Most of the NFIP building standards are performance standards, where general 
requirements are stipulated, but where prescriptive details are not (usually) provided. By and 
large, these general requirements address: 1) the elevation of the lowest floor, 2) the means by 
which a building is elevated to or above the base flood elevation (BFE), i.e., the foundation, and 
3) the materials used below the BFE. It is up to the building designer or contractor, or the 
community floodplain management official, to determine which specific design and construction 
practices meet the general requirements. 
The following NFIP building standards apply to new buildings in any part of the SFHA: 
 The structure must be designed and anchored to prevent flotation, collapse or lateral 
movement of the structure resulting from hydrodynamic and hydrostatic loads, including 
the effects of buoyancy. 
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The Evaluation of the National Flood Insurance Program 
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 The structure must be constructed with materials below the BFE that are flood-damage 
resistant. 
 The structure must be constructed with methods and practices that minimize flood 
damage. 
 Unless located at or above the BFE, utilities and equipment below the BFE must be 
designed and/or located to prevent floodwaters from entering or accumulating within the 
components. 
 Any enclosed spaces below the BFE can only be used for building access, parking and 
storage. 
Manufactured homes must have their lowest floor elevated to or above the BFE if they 
are: 1) placed outside a manufactured home park, 2) placed in a new manufactured home park or 
in an expansion to an existing manufactured home park, and 3) a replacement for a substantially 
damaged home in an existing park.3 Substantially improved manufactured homes must meet the 
same requirements as those homes described above. 
1.2.2. V Zones 
The V zone is known also as the Coastal High Hazard Area (CHHA), and extends from 
offshore to an inland limit based on one or more mapping criteria. The mapping criteria relate to 
high velocity wave action effects (e.g., the 3-foot breaking wave height, the 3-foot wave runup 
depth, or a wave overtopping rate exceeding a threshold rate), and to the physical presence of a 
primary frontal dune (PFD) (FEMA 2003, see Appendix D).4 Although the first generation of 
coastal Flood Insurance Rate Maps (FIRMs) established base flood elevations (BFEs) at the still 
water level and did not account for wave action, wave effects have been incorporated into coastal 
FIRMs since about 1980 (FEMA 2000, see section 7.8.1.3). As used in this study, the term V 
zone includes those zones designated on the FIRM as V, V1-30, VE and VO. 
In addition to the NFIP building standards that apply to all parts of the SFHA, there are 
five additional requirements for new construction in V zones: 
 The elevation of the bottom of the lowest horizontal structural member (supporting the 
lowest floor) must be at or above the BFE. 
3 Manufactured homes in parks predating floodplain management regulations may be exempt from the lowest floor 
elevation requirement. Specifically, manufactured homes placed or substantially improved on sites in an existing 
manufactured home park must have the lowest floor elevated to or above the BFE, or must have the lowest floor 
elevated on reinforced piers no less than 36 inches in height above grade. 
4 All but the last criteria are based on explicit wave effects during the base flood, while the PFD criterion is tied to 
the shoreline morphology rather than a specific flood hazard. See 44 CFR Section 65.11 for a discussion of the PFD. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
 Pile, pier, post or column foundations (i.e., open foundations that allow flood waters 
and waves to pass beneath elevated buildings) must be used.5 The space below the lowest 
floor must be free of obstructions, or constructed with wood latticework, insect screening 
or non-supporting breakaway walls. No fill may be used to elevate or provide structural 
support to a new building in a V zone. 
 When used, any enclosures below the BFE can only be constructed with screening, lattice 
or breakaway walls. Breakaway walls cannot provide vertical support to the building. 
Breakaway walls must satisfy the lateral loading requirements in 44 CFR 60.3(e)(5), i.e., 
they must either break free when exposed to lateral wind and water loads between 10 and 
20 pounds per square foot (psf), or if they are designed to break free at loads greater than 
20 psf, must be certified by a designer to break free during the base flood. 
 The building and its foundation must resist flotation, collapse and lateral displacement 
due to wind and water loads acting simultaneously. A registered architect or engineer 
must develop or review the structural plans, specifications and construction plans, and 
must certify that the design and methods of construction to be used are in accordance 
with accepted standards of practice for meeting the performance requirements. 
In addition to the above design and construction requirements there are two requirements 
related to siting and site alterations in V zones: 
 New construction must be located landward of the reach of mean high tide. 
 Man-made alterations of sand dunes or mangrove stands which would increase potential 
flood damage are prohibited. 
1.2.3. A Zones 
The A zone is that portion of the SFHA that is not subject to high velocity wave action 
during the base flood and is not designated as zone V due to primary frontal dune considerations. 
The source of flooding in an A zone can be a stream or river that overflows its banks; a lake; or 
coastal storm surge accompanied by wave heights and wave runup depths less than 3 feet. As 
used in this study, the term A zone includes those zones designated on the FIRM as A, A1-30, 
A-99, AE, AH, AO and AR. 
In addition to the NFIP building standards that apply to all parts of the SFHA, there are 
several additional requirements for new construction in A zones: 
 The top of the lowest floor, including basement, must be at or above the BFE, unless: 1) 
the community has been granted a basement exception, or 2) the structure is a nonresidential 
structure that is watertight below the BFE with walls that are substantially 
impermeable to the passage of water. 
5 Some solid walls have been allowed below the BFE in V zones. Most commonly, these are shore-perpendicular 
walls required to transmit wind or seismic loads from upper building stories to the soil, fire separation walls required 
by the building code, and walls surrounding stairwells and building egress features. These walls typically are 
associated with large buildings. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
 No restriction on the foundation type is made as long as the building is anchored to the 
foundation and the foundation supports the elevated structure during the base flood event. 
Fill may be used to elevate and provide structural support to a building. 
 Enclosures below the BFE must contain flood openings that allow the automatic entry 
and exit of flood waters. 
 In an AO zone, the top of the lowest floor must be elevated above the highest adjacent 
grade, at least as high as the depth number specified in feet on the FIRM. 
1.2.4. Coastal A Zones 
NFIP regulations treat building standards for A zones in riverine and coastal areas the 
same, and coastal FIRMs do not designate a Coastal A zone. In fact, coastal FIRMs depict A 
zones the same way as inland FIRMs do. The Coastal A zone is a non-regulatory term that has 
been used in recent years to draw a distinction between coastal and inland A zones, and to 
highlight similarities between V zones and A zones in coastal areas. The rationale for these 
efforts is based on a growing body of evidence that flood hazards in coastal A zones are more 
like those in V zones than those in riverine A zones, and that building damages in coastal A 
zones are consistent with those observed in V zones, not riverine A zones (Jones, Coulbourne 
and Tertell 2001; FEMA 2005a). 
Pending formal designation of a Coastal A zone, the following working definition has 
been developed (American Society of Civil Engineers [ASCE], 2005; FEMA, 2005a) and is used 
by this study: area landward of a V zone, or landward of an open coast without mapped V zones. 
In a coastal A zone, the principal source of flooding will be astronomical tides, storm surges, 
seiches or tsunamis, not riverine flooding. During base flood conditions the potential for 
breaking wave heights between 1.5 feet and 3.0 ft will exist. 
NFIP building standards in Coastal A zones are identical to those in A zones -- a coastal 
building in an area subject to a 2.9 ft breaking wave height during the base flood would be 
mapped today as an A zone, and conformance with A zone building standards only would be 
required  despite the fact that breaking waves of that size are capable of destroying or heavily 
damaging typical residential wood-frame walls which could be used as foundation walls in an A 
zone (U.S. Army Corps of Engineers [USACE] 1975; FEMA 2000, see Chapter 11). 

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2. STUDY METHODOLOGY 
This study employed several methods to evaluate NFIP building standards, including: 
 Conducting a literature review documenting: 1) the performance of NFIP 
compliant buildings during flood events, and 2) the costs of elevating those 
buildings on NFIP compliant foundations (see Chapter 3). 
 Meeting with NFIP staff and other experts to discuss building standards in 
floodplain areas. 
 Surveying floodplain professionals regarding NFIP building standards (see 
Appendix A). 
 Conducting a benefit-cost (B/C) analysis of NFIP building standards: 
o Defining a set of typical coastal residential buildings and flood conditions 
for detailed analyses (see Chapter 4). 
o Designing several types of building foundations for the typical 
buildings, under a wide range of flood conditions and freeboard.6 (see 
Chapter 5) 
o Estimating foundation and construction costs for the typical buildings (see 
Chapter 6). 
o Performing benefit-cost analyses to evaluate the use of freeboard and the 
replacement of minimally compliant foundations with improved 
foundations (see Chapter 7). 
 Using an expert panel to guide the study and review its findings. 
FEMA, AIR and the projects expert panel all reviewed the typical buildings and flood 
conditions to be analyzed, and a member of the expert panel performed an independent design of 
selected V zone foundations to verify the studys foundation designs were reasonable. An 
outline of the major components of this study is shown in Figure 1. 
6 As used in this study, freeboard is the height above the BFE to which the lowest floor of a building is raised. 
8 
The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
FIGURE 1. Outline of Benefit-Cost Evaluation Component of NFIP Building Standards 
Design Individual Foundations 
 Calculate flood, wind and other 
loads per FEMA (2000) and 
ASCE (2002) 
 Calculate required foundation 
dimensions to resist loads with 
appropriate safety factors and 
given material properties 
Calculate Construction Costs 
 Adjusted and refined Base Cost of building with standard 
(crawlspace) foundation per Marshall & Swift (2003) 
 Base Cost minus standard foundation cost = Building Only 
Cost 
 Calculate Individual Foundation Costs for slab, pier, wall 
and pile foundations per Marshall & Swift (2003) 
 Add Individual Foundation Costs to Building Only Cost to 
get Final Building Cost for each Combination Analyzed 
Define Buildings to be Analyzed 
 1- and 2-story residences, average to very good quality 
 1,500 to 4,800 sf 
 Slab, wall, pier, pile foundations (per NFIP allowances) 
 Lowest floor elevations (BFE and higher) 
 Hip roofs, 7/12 slope 
Define Flood Conditions 
 Stillwater flood depths 
 Flood Velocities 
 Wave heights and wave crest elevations 
 Local scour at foundations 
 Wind speeds associated with A zone, 
Coastal A zone, V zone 
Identify Building/Flood Combinations for Analyses 
 V zone: 420 combinations 
 Coastal A Zone: 480 combinations 
 A zone: 600 combinations 
Freeboard Costs 
 Calculate incremental costs 
to raise lowest floor by 1 ft, 
2 ft, 3 ft, and 4 ft 
Foundation Change Costs 
 Calculate cost differential 
to substitute one foundation 
type for another 
Benefit-Cost Analyses 
 Use FEMA (2005e) BCA Model 
 Select Discount Rate (7.0%, with sensitivity analysis for 
3.0%, 5.0%, 9.0%) 
 Select Useful Life = 30 years 
 Assume Building Contents Value = 30% of Building Value 
 Normalize all cost and saving inputs as a percent of Final 
Building Cost 
 Define flood depth-frequency relationships for each flood 
zone 
 Define typical ranges of BFEs for coastal floods and Flood 
Hazard Factors (FHFs) for non-coastal floods 
 Define depth-damage curves for each flood zone and 
building type 
 Calculate B/C ratios for adding freeboard or changing 
foundation types, by flood zone 
 Generalize results 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
3. LITERATURE REVIEW 
3.1. Building Performance 
Many publications document building successes and failures during coastal and riverine 
flood events, but the two most useful sources are FEMA and the U.S. Army Corps of Engineers, 
National Floodproofing Committee (USACE, NFPC). 
 FEMA has mobilized its Mitigation Assessment Team (MAT), previously known 
as its Building Performance Assessment Team (BPAT), following severe 
hurricanes and riverine floods. Findings of many of the reports from coastal flood 
events are summarized in chapter 2 of FEMA (2000). MAT reports are available 
at http://www.fema.gov/rebuild/mat/mat_reprts.shtm. 
 FEMA has developed a series of fact sheets and recovery advisories dealing with 
building performance and best practices for construction in floodplains (e.g., 
FEMA, 2005a; FEMA, 2005b; FEMA, 2006a). 
 Many of the NFPC reports are available at 
http://www.usace.army.mil/civilworks/cecwp/NFPC/nfpc.htm . USACE (1998) 
provides an excellent summary of building performance during both riverine and 
coastal flood events. 
The MAT and NFPC documents repeatedly stress the importance of elevating buildings 
above the flood level on adequate foundations, and the importance of using flood-resistant 
materials. Failure to do so results in building damage or loss. This is true especially in riverine 
floods of high velocity, and in coastal areas subject to wave effects. 
The inclusion of wave heights into coastal flood hazard mapping was driven by posthurricane 
Frederic (1979) observations that revealed the frequency and intensity of damage 
inflicted by waves striking coastal buildings that were elevated only to the 100-year storm surge 
stillwater level, in compliance with NFIP requirements at that time (FEMA 2000, see Chapter 
2).7 This is also the reason that the present study devotes much of its attention to building 
standards that mitigate the effect of wave heights. 
3.1.1. Flood Insurance Incentives for Sound Building Practices 
NFIP insurance provisions and premium rates generally encourage sound building 
practices through incentives (e.g., reduced premium rates when the lowest floor is elevated above 
the BFE) and disincentives (e.g., higher premium rates for enclosures below the BFE in V 
zones). The NFIP has also developed some procedures by which policyholders are rewarded 
(through reduced premiums) for adopting design and construction practices which exceed NFIP 
minimum requirements. The V Zone Risk Factor Rating Form (FEMA 2005c) is a good example 
 this form and rating procedure can be used to obtain V zone premium discounts of up to 60% 
7 Wave heights have been included in new coastal flood insurance studies (FISs) and restudies since1980. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
for exceeding NFIP minimum requirements.8 Discounts can be obtained for such things as: siting 
V zone buildings away from the shoreline and out of areas subject to long-term erosion; 
protecting buildings via sand dunes, beach nourishment or erosion control structures; adding 
freeboard; accounting for future conditions in foundation design; increasing foundation 
embedment and pile diameter; designing foundations that require minimal bracing; eliminating 
breakaway enclosures below the BFE, etc. 
Not all NFIP insurance provisions and premium rates promote better construction, 
however. Rogers (2005) has documented one scenario where the NFIP premium rate structure 
discourages a building practice which reduces storm damage to structures. Many reports promote 
the use of pole-type construction, where the pilings extend from in the ground, past the lowest 
floor and to a higher floor or to the roofline. In situation where pole-type construction is used, 
the buildings sometimes are penalized by the NFIP through increased flood premiums and/or 
reduced flood policy coverage for the structure and contents between the lowest floor and the 
floor at the top of the pilings. The effect of this piling penalty has been to encourage builders 
and owners to terminate piling foundations at the BFE, even though continuing the pilings 
upward to a higher floor results in buildings which better resist flood and wind damage. In cases 
where flood levels have exceeded the BFE, buildings with the pilings terminating at the BFE 
have experienced far greater damage than buildings with pilings extending to a higher floor 
(Rogers, 2005; FEMA 2006b). 
3.2. Building Foundations and Construction Costs 
Many publications were found that contain information on the costs of raising existing 
homes on retrofit or replacement foundations. However, relatively few publications contained 
information on foundation costs and freeboard costs for new construction. Information on 
foundation retrofit/building elevation costs, and on new foundations is contained in Table 1 (note 
that the costs included in the table have not been adjusted for inflation). 
These documents suggest that the costs of flood-resistant foundations typically range 
from approximately 5% to 15% of the total building cost for 1- and 2-story residences, and that 
the additional cost of raising homes a few feet at the time of initial construction (adding 
freeboard) is small, usually less than approximately 0.5% to 1% additional for each foot the 
building is raised. 
8 Many of the practices for which premium discounts can be obtained are recommended by the Coastal Construction 
Manual (FEMA 2000) 
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The Evaluation of the National Flood Insurance Program 
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TABLE 1. Literature Review of Costs to Elevate or Change Foundations, Existing Homes and New Construction 
Publication, 
Author, Date 
Building Modification Location Date Cost Comments 
Elevating/Retrofitting Existing Homes 
A 
Floodproofing 
Success Story, 
USACE (1993) 
Elevate 19 existing homes 
(1-story, brick veneer, 
crawlspace foundations) in 
A zone, between 2 and 6 ft 
Dry Creek, 
Goodlettesville, 
TN 
1989 - 1990 $568,000 for 
19 homes 
($30,000 per 
home) 
Homes range from 
1,000 to 1,475 sf in 
size. 
Technical 
Information, 
Elevating 
Substantially 
Damaged 
Buildings in 
Dade County, 
FEMA (1993) 
Raising existing slab-ongrade 
masonry homes 
Miami-Dade 
County, FL 
1992 $30,000 - 
$37,000 to 
raise each 
home up to 3 
ft 
Estimated costs to 
elevate a 2,000 sf 
home. 
Add $1,000 - $1,800 
for each additional ft 
of elevation above 3 ft 
Mitigation 
Success Stories 
III, Assoc. of 
State 
Floodplain 
Managers 
[ASFPM] 
(2000), p. 17 
Elevate 7 existing homes Westport, CT 1994 - 1995 $336,000 for 
7 homes 
($48,000 per 
home) 
Foundation type, flood 
zones and elevation 
raised unknown 
Mitigation 
Success Stories 
III, ASFPM 
(2000), p. 18 
Elevate 15 existing homes Westport, CT 1996 - 1999 $991,000 for 
15 homes 
($66,000 per 
home) 
Foundation type, flood 
zones and elevation 
raised unknown 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 11 
Elevate 41 existing A zone 
homes 
Sacramento 
County, CA 
Post-1997 
flood 
$2.7 million 
for 44 homes 
($61,000 per 
home) 
Foundation type and 
elevation raised 
unknown 
Homeowners 
Guide to 
Retrofitting, 
FEMA (1998), 
p. 44 
Elevate existing wood-frame 
house (on basement or 
crawlspace) by extending 
existing walls 2 feet or 
building an open foundation 
Generic location 1998 $17/sf of 
building 
footprint 
Includes extending 
utilities and adding or 
extending staircases. 
Add 10% for house 
with brick veneer on 
walls 
Add $0.75 per sf of 
building footprint for 
each additional foot of 
elevation up to 8 ft; 
add $1.00 per sf of 
footprint for each foot 
of elevation over 8 ft 
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The Evaluation of the National Flood Insurance Program 
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TABLE 1. Literature Review of Costs to Elevate or Change Foundations, Existing Homes and New Construction 
Publication, 
Author, Date 
Building Modification Location Date Cost Comments 
Homeowners 
Guide to 
Retrofitting, 
FEMA (1998), 
p. 44 
Elevate existing masonry 
house (on basement or 
crawlspace) by extending 
existing walls 2 feet or 
building an open foundation 
Generic location 1998 $35/sf of 
building 
footprint 
Includes extending 
utilities and adding or 
extending staircases. 
Add $0.75 per sf of 
building footprint for 
each additional foot of 
elevation up to 8 ft; 
add $1.00 per sf of 
footprint for each foot 
of elevation over 8 ft 
Homeowners 
Guide to 
Retrofitting, 
FEMA (1998), 
p. 44 
Elevate existing wood-frame 
or masonry house (on slab 
foundation) 2 ft, by raising 
slab and constructing 
foundation walls or open 
foundation 
Generic location 1998 $47/sf of 
building 
footprint 
Includes extending 
utilities and adding or 
extending staircases. 
Add 10% for woodframe 
house with brick 
veneer on walls 
Add $0.75 per sf of 
building footprint for 
each additional foot of 
elevation up to 8 ft; 
add $1.00 per sf of 
footprint for each foot 
of elevation over 8 ft 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 15 
Elevate 15 existing homes in 
V zone onto pile foundations 
Delaware Post-1998 
flood 
$35,000 per 
home 
Elevation raised 
unknown 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 17 
Elevate one existing A zone 
home by 4 ft 
Collier County, 
FL 
Post-1998 
flood 
$54,000 Foundation type 
unknown 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 40 
Elevate four existing A zone 
homes between 4.2 and 8.2 
ft on foundation walls 
Vassar, MI Post-1998 
mitigation 
plan adoption 
$200,000 for 
four homes 
($50,000 per 
home) 
Subgrade basements 
were filled during the 
project 
Non-Structural 
Flood Damage 
Reduction, 
USACE 
(2001), p. 25 
Estimated cost to raise a 
1,200 sf home 10 ft 
Vermilion River 
Basin, Lafayette 
Parish, LA 
1999 $49/sf of bldg 
footprint 
$49/sf cost includes 
$37/sf construction 
cost, + 30% to cover 
design, profit and 
contingencies 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 57 
Elevate one existing A zone 
home by approximately 5-6 
ft 
Glasgow, MT 2000 $88,000 Subgrade basement 
was filled, house was 
elevated (foundation 
type not stated) 
Mitigation 
Success Stories 
IV, ASFPM 
(2002), p. 89 
Elevate 10 existing A zone 
homes 
King County, 
WA 
2000 - 2001 $568,000 for 
10 homes 
($57,000 per 
home) 
Foundation types and 
elevations raised 
unknown 

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The Evaluation of the National Flood Insurance Program 
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TABLE 1. Literature Review of Costs to Elevate or Change Foundations, Existing Homes and New Construction 
Publication, 
Author, Date 
Building Modification Location Date Cost Comments 
New Construction 
Elevating to the 
Wave Crest 
Level: A 
Benefit-Cost 
Analysis, 
FEMA (1980) 
Study examined the costs 
and benefits of elevating a 
1,500 sf residential structure 
from the stillwater level to 
the wave crest level, over a 
range of BFEs and coastal 
erosion conditions 
V zone and A 
zone 
1979 B/C of 
elevating to 
the wave crest 
level ranged 
from 1.0 to 
8.2 based on 
flood damage 
reduction 
alone, and 
from 1.4 to 
9.5 based on 
flood 
premium 
savings alone 
Hurricane Frederic 
(1979) destroyed many 
pile-elevated, NFIP 
compliant homes in 
Gulf Shore, AL (at that 
time the NFIP only 
mandated elevation to 
the stillwater level). 
Coastal 
Construction 
Manual, FEMA 
(1986), 
Appendix F 
Timber piles, installed (8 in 
square, 10 in square and 8 in 
round) 
Generic 1985 $5/lf to $13/lf Coastal home 
construction cost 
estimates 
Coastal 
Construction 
Manual, FEMA 
(1986), 
Appendix F 
Precast concrete piles, 
installed (8 in square to 10 
in square) 
Generic 1985 $7/lf to $16/lf Coastal home 
construction cost 
estimates 
Coastal 
Construction 
Manual, FEMA 
(1986), 
Appendix F 
Reinforced concrete 
masonry piers (12 x 12 in or 
16 x 16 in) 
Generic 1985 $20/lf to 
$50/lf 
Coastal home 
construction cost 
estimates 
Homebuilders 
Guide to 
Coastal 
Construction, 
Fact Sheet 6, 
FEMA (2005b) 
Cost differential between a 
slab or crawlspace 
foundation and a pile or 
column foundation  A zone 
3,000 sf home, homes 
elevated to the same height 
above grade 
Generic 2005 Adds > 2% to 
building cost 
Consensus estimate by 
a group of designers 
and industry experts 
A Comparative 
Cost Evaluation 
of Foundation 
Types 
Permitted by 
NFIP 
Regulations in 
Coastal A 
Zones and V 
Zones, FEMA 
(2005d)  see 
Appendix 2 
Cost differential to add 
freeboard or change 
foundation types 
Coastal A zones 
and V zones 
2005 The 
additional 
cost of 
constructing a 
V zone 
foundation 
instead of an 
A zone 
foundation 
varies from 
approx. 2% to 
10%+ of the 
base building 
cost 
A zone foundations 
include slab, masonry 
piers and 8 masonry 
wall/piers. V zone 
foundations include 
10 and 12 timber 
piles, 8 and 10 steel 
H piles, 10 and 12 
precast concrete piles. 
Each foot of freeboard 
above the BFE adds 
from 0.3% to 0.5% of 
the base building cost. 
NOTE: Retrofitting and new construction costs cited in the table are not adjusted for inflation.
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The Evaluation of the National Flood Insurance Program 
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4. DEFINING TYPICAL BUILDINGS AND FLOOD CONDITIONS FOR 
THIS STUDY 
The major effort of this study  the benefit-cost analysis of NFIP building standards  
was designed to be representative of a wide range of residential homes sited in floodplain areas. 
Representative building characteristics and flood conditions to which the buildings would be 
subject, were defined at the beginning of the project by the study team, the expert panel and 
FEMA staff. 
4.1. Buildings Evaluated in this Study 
Buildings used in this study include can be characterized as 1- and 2-story residences, 
rectangular in shape, between 1,500 and 4,800 square feet (sf) in size, and situated in V zones, 
Coastal A zones and A zones.9 All homes were given hip roofs with a 7/12 roof pitch. Most of 
the effort in this study was devoted to evaluating the costs and benefits of adding freeboard and 
changing foundation types to these buildings. Figure 2 and Table 2 illustrate pertinent 
dimensions for the buildings evaluated in this study. 
TABLE 2. Dimensions of Buildings Used in this Study 
Building Case Length (ft) Width (ft) Number of 
Stories 
Footprint Size 
(sf) 
Building Size (sf) 
1 50 30 1 1,500 1,500 
2 50 30 2 1,500 3,000 
3 60 40 1 2,400 2,400 
4 60 40 2 2,400 4,800 
9 This study did not consider repairs, retrofits, improvements or additions to existing buildings. 
FIGURE 2. Building Footprint (source: FEMA 1998, p.44) 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
These four building types were placed on between three and six foundation types in each 
of the three flood hazard zones investigated. Lowest floor elevations for each 
building/foundation/zone combination were varied from the BFE to four feet above the BFE, in 
1-ft increments (see Table 3).10 Four to seven flood conditions (see Section 5.2) were applied to 
each building/foundation/zone/floor combination. A total of 1,500 combinations of buildings and 
flood conditions were evaluated fully, not counting the sensitivity analyses run during the benefit 
cost portion of the study. 
TABLE 3. Building/Foundation/Flood Zone/Floor Elevation/Flood Condition Combinations Analyzed in this Study 
Flood Hazard 
Zone Building Sizes Foundation Types Lowest Floor 
Elevations 
Flood 
Conditions 
Building 
Combinations 
Analyzed 
V 
4 
(see Table 2) 
Timber Pile 
Concrete Pile 
Masonry Pier 
BFE 
BFE + 1 ft 
BFE + 2 ft 
BFE + 3 ft 
BFE + 4 ft 
7 
(see Table 4) 
420 
Coastal A 
4 
(see Table 2) 
Timber Pile 
Concrete Pile 
Masonry Pier 
8 Masonry Wall 
12 Masonry Wall 
Fill and Concrete Slabon-
Grade 
BFE 
BFE + 1 ft 
BFE + 2 ft 
BFE + 3 ft 
BFE + 4 ft 
4 
(see Table 4) 
480 
A 
4 
(see Table 2) 
Timber Pile 
Concrete Pile 
Masonry Pier 
8 Masonry Wall 
12 Masonry Wall 
Fill and Concrete Slabon-
Grade 
BFE 
BFE + 1 ft 
BFE + 2 ft 
BFE + 3 ft 
BFE + 4 ft 
5 
(see Table 4) 
600 
10 Foundation and cost calculations were run on two floor elevations below the BFE (BFE  1 ft, BFE  2 ft) for A 
zones and Coastal A zones, but these floor elevations were not used in subsequent analyses. Buildings like this 
would not be permitted in the SFHA. 
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The Evaluation of the National Flood Insurance Program 
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4.2. Flood and Wind Conditions Evaluated in this Study 
Sixteen different flood conditions and two different wind conditions were used to 
design the foundations listed in Table 3.11 Key terms for these flood and wind conditions are 
defined below, are illustrated in Figure 3 and are listed in Table 4. 
Flood Hazard Zone: V zone, Coastal A zone and A zone (see descriptions in Sections 
1.2.2, 1.2.3 and 1.2.4). 
Associated Wind Speed: the 3-second gust wind speed used in the foundation design 
calculations for each flood hazard zone (110 mph in the A zone, and 130 mph in the V 
zone and Coastal A zone). 
Flood Condition: a set of flood depth, flood velocity, wave height and scour conditions 
used in the foundation design analyses. There are 16 flood conditions used in this study, 
seven in V zones, four in Coastal A zones and 5 in A zones. Flood conditions within each 
zone are numbered, with the lower numbers corresponding to the least severe conditions, 
and the highest numbers corresponding to the most severe conditions. 
Stillwater Depth: the vertical distance (ft) between the ground elevation and the stillwater 
elevation. The stillwater elevation is the elevation of the flood water surface, with wave 
effects damped out. 
BFE Depth: the vertical distance (ft) between the ground elevation and the wave crest 
elevation. 
Wave Height: the vertical distance (ft) between the wave crest and the wave trough. 
Flood Velocity: the velocity (ft/sec or fps) at which flood waters flow across the ground. 
This study assumed the velocity was constant throughout the water column. 
Scour: localized erosion depth (ft) caused by flood flow and/or waves interacting with the 
building foundation. 
Floodborne Debris: each foundation was also subject to impact from a 1,000 lb object 
floating at the stillwater level, traveling at the specified flood velocity. 
Windborne Debris: the study did not consider windborne debris effects on the buildings 
analyzed, and assumed all building envelopes above the lowest floor would remain intact. 
11 As used in this report, design includes the calculation of foundation characteristics and dimensions (e.g., pile 
diameter; pile embedment; pier and wall footing sizes and embedment; slab thickness; fill quantities, slopes and 
protection). Detailed designs with construction drawings and specifications were not developed. 
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The Evaluation of the National Flood Insurance Program 
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FIGURE 3b. A Zone Flood Conditions Modeled During this Study 
Flood Conditions (see Table 4 for complete list of conditions) 
A-1 A-2 A-3 A-4 A-5 
BFE = SWL 
2.0 
3.7 
6.0 
8.0 
10.0 
Wind = 110 mph 
Grade 
Flow 
Vel. 
FIGURE 3a. V Zone and Coastal A Zone Flood Conditions Modeled During this Study 
Wave crest ~ BFE 
SWL 
Grade 
3.0 
1.9 2.8 
4.3 
5.7 
3.7 
Coastal A Zone V Zone 
6.2 
4.0 
5.1 
7.9 
6.4 
9.9 
CA-1 CA-2 CA-3,4 V-1,2 V-3,4 V-5,6,7 
Flood Conditions (see Table 4 for complete list of conditions) 
Wind = 130 mph 
Wave 
Height 
Flow 
Vel 
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The Evaluation of the National Flood Insurance Program 
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TABLE 4. Flood and Associated Wind Conditions Used by this Study to Develop and Cost Building Foundations 
Flood 
Hazard Zone 
and 
Associated 
Wind Speed 
Flood 
Condition 
Stillwater 
Depth (ft) 
BFE Depth 
(ft) 
Wave Height 
(ft) 
Flood 
Velocity (fps) Scour (ft) 
V-1 4.0 6.2 3.0 3.0 3.0 
V-2 4.0 6.2 3.0 6.0 4.0 
V-3 5.1 7.9 4.0 4.0 3.0 
V-4 5.1 7.9 4.0 6.0 4.0 
V-5 6.4 9.9 5.0 4.0 4.0 
V-6 6.4 9.9 5.0 6.0 5.0 
V Zone 
(130 mph) 
V-7 6.4 9.9 5.0 8.0 6.0 
CA-1 1.9 3.0 1.5 2.0 1.0 
CA-2 2.8 4.3 2.2 3.0 2.0 
CA-3 3.7 5.7 2.9 3.0 3.0 
Coastal A 
Zone 
(130 mph) 
CA-4 3.7 5.7 2.9 6.0 4.0 
A-1 2.0 2.0 0.0 2.0 0.0 
A-2 3.7 3.7 0.0 3.0 0.0 
A-3 6.0 6.0 0.0 3.0 0.0 
A-4 8.0 8.0 0.0 4.0 0.0 
A Zone 
(110 mph) 
A-5 10.0 10.0 0.0 4.0 0.0 

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The Evaluation of the National Flood Insurance Program 
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4.2.1. V Zone 
There are seven V zone flood conditions used in this study, with the intensity of the flood 
effects increasing from the landward side of the V zone (conditions V-1 and V-2) toward the 
seaward direction. All V zone conditions were developed with depth-limited breaking waves. 
The first two conditions, V-1 and V-2, represent minimal V zone conditions; the 
stillwater depth is 4.0 ft, enough to support a 3.0 ft breaking wave height (the minimum wave 
height necessary for an area to be mapped as a V zone)12. The BFE Depth (vertical distance 
between the wave crest elevation and the ground) is 6.2 ft for these conditions, and a building 
here would have to have the bottom of the floor beam supporting the elevated floor 6.2 ft above 
the ground. Condition V-1 assumes a flood flow velocity of 3.0 fps and local scour of 3.0 ft 
around a foundation element. Condition V-2 assumes a flood flow velocity of 6.0 fps and 4.0 ft 
of local scour. 
The V-3 and V-4 conditions account for another 1.1 ft of stillwater depth, which is 
accompanied by 4.0 ft breaking waves and a BFE depth 7.9 ft above the ground. Condition V-3 
assumes a flood flow velocity of 4.0 fps and local scour of 3.0 ft, while condition V-4 assumes a 
flood flow velocity of 6.0 fps and 4.0 ft of local scour. 
The V-5, V-6 and V-7 conditions are the most extreme ones evaluated, and represent the 
case where the bottom of the floor beam supporting the elevated floor would have to be above 
the crest of a 5.0 ft breaking wave, with its crest 9.9 ft above grade. Flood velocities and local 
scour range from 4.0 fps to 8.0 fps and 4.0 ft to 6.0 ft, respectively. This situation is 
representative of the most severe V zone conditions likely to be seen by buildings in most coastal 
areas.13 
4.2.2. Coastal A Zone 
There are four Coastal A zone flood conditions used in this study, with the intensity of 
the flood effects decreasing in the inland direction from the seaward boundary of the Coastal A 
zone (coincident with the landward side of the V zone). Conditions CA-3 and CA-4 are 
incrementally less severe than, but roughly equivalent to, conditions V-1 and V-2. 
Stillwater depths, wave heights, wave crest elevations, flow velocities and local scour all 
decrease through the Coastal A zone to the location where condition CA-1 occurs. Condition 
CA-1 represents the landward limit of the Coastal A zone, where the wave height is 1.5 ft (ASCE 
2005). Inland of this point the energy in the waves diminishes rapidly and A zone foundations 
typically are adequate (FEMA 2005a). Like V zone conditions, Coastal A zone conditions were 
developed with depth-limited breaking waves. 
12 A shallower stillwater depth and the corresponding smaller wave height would cause this site to be classified as a 
Coastal A zone. 
13 Granted, some buildings may see more severe V zone conditions during the base flood, but condition V-7 likely 
captures the vast majority of extreme V zone situations experienced by buildings constructed on land. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
4.2.3. A Zone 
There are five A zone flood conditions used in this study. All are specified based on 
stillwater depth and flow velocity only, there are no breaking waves or scour effects included. 
Stillwater flood depths range from 2.0 ft above grade (condition A-1) to 10.0 ft above grade 
(condition A-5). This range of conditions likely includes those base flood conditions experienced 
by the majority of structures placed in non-coastal (riverine and lake) A zones. Comparison of 
conditions A-1 and CA-1, and A-2 and CA-3 and CA-4, will reveal the influence of waves and 
scour on foundation design and costs. 

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The Evaluation of the National Flood Insurance Program 
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5. FOUNDATION DESIGNS 
Individual foundations were designed14 for each building type, in each flood zone, for 
each flood condition, and for each floor elevation. Designs were based on: 
 Flood, wind and other loads were calculated according to ASCE 7-02, Minimum 
Design Loads on Buildings and Other Structures (ASCE 2002) and the Coastal 
Construction Manual (FEMA 2000). Breaking wave, hydrodynamic and debris 
impact loads were included. Calculation of hydrostatic loads was not required 
since pile and pier foundations are not subject to hydrostatic loads, and since wall 
foundations were assumed to have flood openings, as required by the NFIP. 
 Wind speeds used in the analyses were 3-second gust speeds at a 30-ft elevation 
in exposure category C. The wind speed used in V zone and Coastal A zone 
designs was 130 mph; the wind speed used in A zone designs was 110 mph. 
 Buildings were assumed to be enclosed and wind loads were calculated using a 
7/12 roof pitch. 
 Typical soil conditions were assumed and soil properties were taken from the 
Naval Facilities Engineering Command reference Foundations and Earth 
Structures (NAVFAC 1982). 
 All loads and conditions were used to calculate stable foundation dimensions, or 
if stability was not possible under the specified flood and scour conditions, this 
was noted during the analysis.15 
5.1. Pile Foundations 
This study evaluated both treated timber and precast concrete piles in all flood hazard 
zones. All piles were spaced 10 feet apart. Piles at least 12 inches in diameter were used in this 
study, and for ease of computations, uniform piles were assumed (tapered piles were not used). 
In some cases, lateral loads (wind and flood) were high enough to lead to pile failure via bending 
stresses in excess of the allowable value  in these cases, pile diameters were increased to the 
point where the stress was within the allowable limits (in the real world, a designer might reduce 
the pile spacing instead). Calculations showed consistently that the wind load on the building 
controlled the pile foundation design. 
14 Each design was based on the combination of factors mentioned previously and was not intended to be a precise 
design. Instead, the method used here is intended to provide a reasonable and consistent approximation of what an 
actual design would be. 
15 Foundation stability was problematic when typical pier and wall foundations were used outside of A zones. 
Typical 16 x 16 masonry piers were found to be inadequate against larger wave heights, and would be undermined 
by most Coastal A Zone and V zone conditions specified herein. Typical wall foundations would be undermined 
and/or fail due to lateral loads under the more energetic Coastal A zone conditions. Unlike pile foundations (where a 
design was always determined in this study) adequate wall and pier designs were not determined by this study since 
the pier size, wall thickness and embedment requirements far exceeded what most designers and contractors would 
use. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
In V zones, timber and concrete pile embedment requirements (below the specified scour 
depth) were approximately linear with increasing freeboard, for all building sizes and flood 
conditions (see Figure 4 for typical results). In Coastal A zones (see Figure 5 for typical results), 
calculated pile embedments (below specified scour depths) for conditions CA-3 and CA-4 tended 
to resemble the embedments required for V zone conditions V-1 and V-2. This is consistent with 
the fact that these locations were close to each other, on opposite sides of the V zone - Coastal A 
zone boundary (see Figure 3). Pile embedment at the landward boundary of the Coastal A zone 
(condition CA-1) was similar to the calculated pile embedment in A zones, with only a shallow, 
uniform embedment requirement across all freeboard values. Pile embedment for condition CA-2 
typically fell between CA-1 and CA-3. 
It should be noted that even though 12 inch pile diameters were used for all flood zones 
in this study, 12 inch diameter piles were not required to resist the loads in A zones16. Thus, the 
costs of the A zone pile foundations (see Chapter 6) may be greater than the costs using adequate 
designs with smaller diameter piles. Looking toward to the benefit-cost discussion, if an A zone 
pile foundation using 12-inch piles is justified economically, a less expensive pile foundation 
will also be justified. 
5.1.1. Pile Design Review 
Upon completion of the initial pile foundation designs, one member of the projects 
Expert Panel (a structural engineer) reviewed the design methodology in detail. As part of the 
review, 14 timber pile designs were selected (10% of the V zone timber pile cases) and an 
independent pile design -- determination of pile diameter and pile embedment depth -- was 
completed for each. The selected cases spanned the range of building size, floor elevation and 
flood condition parameters being considered by this study. The independent review for the 14 
cases used a more rigorous design methodology than that employed in this study, as a check on 
the design assumptions and approximations used in this study.17 A comparison of the results of 
the two designs for the 14 selected case shows: 
 Pile embedments determined by this study were greater than the independent 
embedment calculation in ten cases (by an average of 8.1 ft) and less in four cases (by 
an average of 5.3 ft). 
 Pile diameters determined by this study were greater than the independent diameter 
calculation in seven cases (by an average of 0.9 in), equal in six cases, and less than 
the independent calculation in one case (by 1.2 in). 
16 Lower wind speeds and the absence of waves and scour in A zones resulted in loads that could be resisted by 
smaller diameter piles. Twelve-inch piles were typically required for the foundations in V zones and Coastal A 
zones due to higher wind speeds, coupled with wave and scour effects. 
17 The foundation design methodology employed in this study used some approximations and assumptions to 
simplify and expedite the design of hundreds of foundations. While this methodology was slightly different than a 
detailed foundation design for an actual structure, the results appeared reasonable and were verified by the 
independent review. 
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The Evaluation of the National Flood Insurance Program 
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FIGURE 4. Pile Embedment Depth (ft) vs. Floor Elevation, 
V Zone, 50'x30', 1 Story - Timber Piles 
4
8 
12 
16 
20 
24 
28 
0 1 2 3 4 
Floor Elevation (ft above BFE) 
Pile Embedment Depth (ft) 
Condition V-1 
Condition V-2 
Condition V-3 
Condition V-4 
Condition V-5 
Condition V-6 
Condition V-7 
FIGURE 5. Pile Embedment Depth (ft) vs. Floor Elevation 
Coastal A Zone, 50'x30', 1-Story, Timber Piles 
2
4
6
8 
10 
12 
14 
16 
0 1 2 3 4 
Floor Elevation (ft above BFE) 
Pile Embedment Depth (ft) 
Condition CA-1 
Condition CA-2 
Condition CA-3 
Condition CA-4 

26 
The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
 The independent reviewer also recalculated the 14 cases while allowing the minimum 
pile diameter to vary (as a check on the study constraint that timber pile diameters 
must be greater than or equal to 12 inches). Recalculated pile diameters still equaled 
or exceeded 12 inches in nine of the 14 cases; in the remaining five cases, pile 
diameters varied between 9.9 and 10.8 inches. 
Based on the independent check, the studys pile design methodology was judged by the study 
leader to be appropriate for this study. On the whole, this studys pile design methodology was 
slightly more conservative (i.e., resulting in greater pile embedment and or diameter) than the 
more detailed independent design, and where study embedment depths or pile diameters were 
less than the corresponding independent results, those differences usually were small. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
5.2. Masonry Pier Foundations 
This study evaluated reinforced concrete masonry piers in all flood hazard zones. 
Masonry piers were assumed to be consistent with standard practice in many V zones -- 16 
inches square in cross-section, and spaced at 10 feet on center. Loads were applied to piersupported 
buildings in a fashion similar to the pile-supported buildings. Calculations showed pier 
cross sections larger than 16 inches square would be required for scenarios with high freeboard 
at the more energetic V zone conditions V-5, V-6 and V-7. Larger piers typically are not 
observed in coastal construction, indicating that standard practice may not be adequate to resist 
flood and wind loads in V zones, where the BFE is one story or higher above the ground. 
Pier foundations in V zones and Coastal A zones can be deficient in another way, also. 
The pier footings used in this study were similar to those commonly constructed in the field (3-ft 
square footings, 8-in thick and 30 inches below grade). Calculations in this study showed that 
these footings were not adequate to resist V zone and Coastal A zone scour and overturning 
forces on the building. Post-storm investigations reveal that these footings are not capable of 
resisting the scour specified for the V zone and Coastal A zone flood conditions in this study (see 
the Homebuilders Guide to Coastal Construction, Fact Sheets 11 and 14 [FEMA 2005b]). Thus, 
use of the typical pier foundations and footings is not recommended under those conditions 
specified herein for V zones and Coastal A zones.18 Pile foundations, or modified pier 
foundations such as those contained in FEMA (2006b), are recommended in these situations. 
This study found typical pier foundations designed in accordance with sound engineering 
practice to be adequate in A zone conditions not subject to waves and scour. 
5.3. Wall Foundations 
This study evaluated the use of 8-inch and 12-inch thick concrete masonry perimeter wall 
foundations (with masonry piers supporting the interior of the buildings) in A zones and Coastal 
A zones. The walls were supported on conventional spread footings. Wall foundations modeled 
in this study for A zone conditions were found to be adequate, but like the masonry pier 
foundations, typical perimeter wall foundations in Coastal A zone conditions could not resist the 
scour and wave loads and thus are not recommended in Coastal A zones (they are prohibited by 
the NFIP in V zones). Cost calculations in this study will understate the actual costs for wall 
foundations required to resist Coastal A Zone flood and scour conditions. 
5.4. Elevation on Fill (Concrete Slabs) 
Elevation of concrete slabs (4-inch thick) on fill were evaluated during this study for A 
zones and Coastal A zones. The slabs were elevated to the BFE and above using compacted fill, 
with the top of the fill pad extending beyond the building footprint 10 ft in all directions, and 
with side slopes of 1:3 (vertical:horizontal). Fill stabilization (with vegetation) was assumed in 
18 Nevertheless, typical (i.e., often inadequate) masonry pier foundations were carried through the foundation cost 
analysis portion of this study. Given the calculated and observed failures of these foundations in V zones and some 
Coastal A zones, the foundation cost results understate the required dimensions and costs for these foundations. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
the Coastal A zone. Elevation of slabs by fill was not evaluated for V zones because they are 
prohibited by the NFIP. 
This study found that relatively large quantities of fill are required to elevate homes more 
than a few feet above existing grade (see Figure 6). Thus, if the BFE is as shown in conditions 
A-3, A-4 or A-5 (six to 10 feet above grade), use of a slab foundation elevated on fill is not 
practical, even before freeboard considerations are included. Foundation cost estimates (see 
Chapter 7) verify this. 
FIGURE 6. Fill (cy) Required to Elevate Slab Foundation, 50'x30' Building Footprint, Top of 
Fill Pad Extends 10 ft Beyond Footprint in All Directions, 1:3 Side Slopes 
0 
1,000 
2,000 
3,000 
4,000 
5,000 
6,000
0 1 2 3 4 
Top of Slab Elevation (ft above BFE) 
Cubic Yards (cy) of Fill 
Condition A-1 
Condition A-2 
Condition A-3 
Condition A-4 
Condition A-5 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 
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The Evaluation of the National Flood Insurance Program 
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6. BUILDING COSTS 
6.1. A Note about Building Costs19 and This Study 
The benefit-cost calculations made during this study were structured so that all dollar 
inputs are expressed as a percentage of the initial building cost, not in absolute dollar terms. This 
approach helps to generalize the results of the study, and extends the applicability of its results 
beyond the year upon which the studys building cost data were obtained. 
Since this study began in 2003, all building costs, including foundation costs, were 
calculated using data and procedures from Marshall & Swift (2003), supplemented where 
necessary, with other data. This approach provides a consistent building valuation procedure, 
which is useful for making relative cost comparisons when freeboard and alternate foundations 
are considered. The presumption that todays (or future) foundation and freeboard costs remain 
relatively constant (in percentage terms) when compared with the entire building cost is a 
reasonable assumption. 
Finally, although the 2003 per-square-foot building costs cited in this chapter may appear 
low (especially given todays residential construction costs and massive reconstruction looming 
on the horizon following back-to-back severe hurricane seasons in 2004 and 2005) the study 
methodology produces generic benefit-cost results that are not tied to 2003 building cost data or 
to any specific point in time. 
6.2. Building Cost Calculation Procedure 
Building costs were developed in this study for the typical buildings shown in Table 2 on 
a variety of foundation types. This involved a process where final or total building costs were 
built-up using Marshall & Swift (2003) costs calculation procedures. The process is illustrated 
in the Calculate Construction Cost box in Figure 120. 
6.2.1. Key Cost Definitions 
Base Cost 
June 2003 building cost (see Table 5, upper) for each of the building sizes (see Table 2) 
calculated using Marshall & Swifts (2003) Residential Cost Handbook. Each building is placed 
upon the standard Marshall & Swift foundation -- a crawlspace with interior piers (see Figure 7). 
A quality of construction adjustment was included in the base building cost as a proxy for 
differences between typical buildings constructed in various flood hazard zones. Other cost 
19 All building costs in this study exclude the costs of the land upon which the buildings are placed. 
20 A fundamental assumption of this study is that the building (and its costs) can be separated into its foundation, and 
everything else above the foundation (floor system, walls, roof, interior components and systems, etc.). This 
assumption is consistent with the segregated cost method contained in Marshall & Swift (2003), where the 
foundation cost for the base building can be computed separately from the cost of other building elements. Thus, if 
the base foundation cost is computed separately and deducted from the base building cost, this leaves the cost of the 
building without a foundation. Other foundations can be placed beneath the building, costs can be calculated for the 
building plus the other foundation, and cost comparisons can be made. 
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The Evaluation of the National Flood Insurance Program 
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adjustments were made to the base building cost for floor coverings, floor insulation, hurricane 
connectors and heat pumps, all using Marshall & Swift data and procedures. 
Refined Cost 
The base building cost, refined to include numbers of appliances and plumbing fixtures that 
deviate from the Marshall & Swift default numbers. Table 5 (lower) shows the June 2003 refined 
building costs developed using the Marshall & Swift data and procedures. Note that although 
these refinements were made in an attempt to characterize typical homes in each flood hazard 
zone, the net effect of the refinements was small, adding approximately $2/sf to $3/sf to the 
Marshall & Swift base costs. 
Standard Foundation Cost 
The June 2003 cost for the standard foundation was determined using Marshall & Swift (2003) 
procedures and is shown in Table 6 (upper). Its cost was modest, estimated at $2.09/sf to $2.65/sf 
for the typical buildings evaluated in this study. 
Building Only (without Foundation) Cost 
The cost of the building without the standard foundation (see Table 6, lower). 
Individual Foundation Cost 
The cost of an individual slab, pier, wall or pile foundation, estimated using Marshall & Swift 
(2003) data and procedures. Individual foundations and their costs are discussed in Section 6.3. 
Final Building Cost 
The built-up cost of the building only cost, plus the individual foundation cost. Final costs are 
discussed in Section 6.3. 
6.2.2. Construction Quality 
Descriptions of each of the construction qualities used in this study have been extracted 
from Marshall & Swift (2003) and are included below. This study assumed the following 
qualities of construction: V zone = very good quality; Coastal A zone = good quality; A zone = 
average quality21. 
Average Quality 
Usually mass produced and will meet or exceed the minimum construction requirements of 
lending institutions, mortgage-insuring agencies and building codes; by most standards, the 
21 Prior to the development of the generalized benefit-cost calculation procedure, discussions with project reviewers 
indicated their desire to see additional calculations made using good and very good quality homes in A zones. 
However, the benefit-cost procedure developed in this study does not depend on actual construction costs  all 
incremental costs and savings have been normalized with respect to the total construction cost for a home  and 
these additional quality calculations were not required. 
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The Evaluation of the National Flood Insurance Program 
Evaluation of the National Flood Insurance Programs Building Standards 
quality of materials and workmanship is acceptable but does not reflect custom craftsmanship; 
cabinets, doors, hardware and plumbing are usually stock items; residences of average quality 
will be encountered more frequently than residences of other qualities. 
Good Quality 
May be mass produced in above-average residential developments or built for an individual 
owner; good quality standard materials are used throughout; they will exceed the minimum 
construction requirements of lending institutions, mortgage-insuring agencies and building 
codes; some attention is given to architectural design in both refinements and details; interiors 
are well finished; exteriors have good fenestration with ornamental materials or other 
refinements. 
Very Good Quality 
Typical of those built in high-quality tracts or developments and are frequently individually 
designed; attention has been given to interior refinements and details; exteriors have good 
fenestration with some custom ornamentation. 
FIGURE 7. Marshall & Swift (2003) base foundation elements 
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The Evaluation of the National Flood Insurance Program 
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TABLE 5. Construction Costs* of Buildings Used in this Study (2003) 
A Zone (Average Quality) Coastal A Zone (Good 
Quality) 
V Zone (Very Good 
Quality) 
Building 
Case 
Description 
M&S cost 
($/sf)1 
Cost ($) M&S cost 
($/sf)1 
Cost ($) M&S cost 
($/sf)1 
Cost ($) 
Base Cost 
1 30x50, 1-story, 
1,500 sf 
63.99 95,980 87.91 131,859 106.92 160,382 
2 30x50, 2-story, 
3,000 sf 
54.41 163,233 75.54 226,611 97.15 291,438 
3 40x60, 1-story, 
2,400 sf 
58.81 141,145 81.23 194,947 98.52 236,452 
4 40x60, 2-story, 
4,800 sf 
50.17 240,825 69.86 335,334 89.82 431,124 
Refined Cost 
1 30x50, 1-story, 
1,500 sf 
66.76 100,128 90.06 135,088 107.94 161,906 
2 30x50, 2-story, 
3,000 sf 
56.66 169,979 77.96 233,856 100.08 300,229 
3 40x60, 1-story, 
2,400 sf 
61.26 147,025 83.69 200,853 100.71 241,717 
4 40x60, 2-story, 
4,800 sf 
52.48 251,903 72.77 349,283 93.57 449,134 
* Base costs reported here include Marshall & Swift (2003) base costs, plus adjustments for floor coverings, floor insulation, 
hurricane connectors and heat pumps. Refined costs include adjustments for appliances and plumbing fixtures deemed typical for 
the residences used in this study. 
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The Evaluation of the National Flood Insurance Program 
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TABLE 6. Construction Costs without Marshall and Swift (2003) Foundation 
A Zone (Average Quality) Coastal A Zone (Good 
Quality) 
V Zone (Very Good 
Quality) 
Building 
Case 
Description 
M&S cost 
($/sf)1 
Cost ($) M&S cost 
($/sf)1 
Cost ($) M&S cost 
($/sf)1 
Cost ($) 
Foundation Cost 
1 30x50, 1-story, 
1,500 sf 
2.65 3,975 2.65 3,975 2.65 3,975 
2 30x50, 2-story, 
3,000 sf 
2.09 6,270 2.09 6,270 2.09 6,270 
3 40x60, 1-story, 
2,400 sf 
2.65 6,360 2.65 6,360 2.65 6,360 
4 40x60, 2-story, 
4,800 sf 
2.09 10,032 2.09 10,032 2.09 10,032 
Building Only Cost (without Foundation) 
1 30x50, 1-story, 
1,500 sf 
64.10 96,153 87.41 131,113 105.29 157,931 
2 30x50, 2-story, 
3,000 sf 
54.47 163,709 75.86 227,586 97.99 293,959 
3 40x60, 1-story, 
2,400 sf 
58.61 140,665 81.04 194,493 98.07 235,357 
4 40x60, 2-story, 
4,800 sf 
50.39 241,871 70.68 339,251 91.48 439,102 

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6.3. Foundation Costs and Final Building Costs 
The next step in the study was to take the individual foundations designed (for the 
various combinations of building size, flood zone, flood conditions and floor elevation), to 
estimate their costs, and to combine building only costs with foundation costs. Basic 
assumptions, a few examples and summary tables are given below. 
6.3.1. Pile Foundations 
Unit costs for 12-in timber and concrete piles are given in Table 7. These values were 
used in conjunction with the required pile length (embedment depth + length out of the ground) 
and the number of piles to calculate individual pile foundation costs. Pile foundation cost 
calculations assumed that a minimum embedment depth would be 6.0 ft into the ground, even if 
individual pile design embedment calculations showed less embedment was adequate to resist 
the applied loads. Pile foundation costs were based on 24 piles beneath the 1,500 sf and 3,000 sf 
buildings, and 35 piles beneath the 2,400 sf and 4,800 sf buildings. In instances where calculated 
pile diameter requirement exceeded the 12-inch initial estimate, the unit costs were multiplied by 
the ratio of the required pile cross-sectional area to the cross-sectional area of the 12-inch pile. 
TABLE 7. 2003 Unit Costs for Pile Foundations 
Pile Setup Cost ($) Material Cost 
($/lf) 
Driving Cost 
($/lf) 
Timber 10,150 11.48 6.73 
Concrete 11,310 13.63 8.47 
Calculated timber pile foundation costs for the 1,500 sf, 1-story V zone building are 
shown in Figure 8. These costs translate into a range of approximately $9/sf to $17/sf for the 
building. Note the similar shapes of the curves to the pile embedment curves in Figure 4. By 
adding the foundation costs to the base-building-minus-foundation cost ($157,931 from Table 6), 
the final building costs can be obtained. These results are shown in Figure 9. 

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FIGURE 8. Timber Pile Foundation Cost vs. Floor Elevation, 
V Zone, 50'x30', 1 Story (Bldg. cost without foundation = $157,931) 
$12,000 
$14,000 
$16,000 
$18,000 
$20,000 
$22,000 
$24,000 
$26,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Pile Foundation Cost 
Condition V-1 
Condition V-2 
Condition V-3 
Condition V-4 
Condition V-5 
Condition V-6 
Condition V-7 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 
FIGURE 9. Final Building Cost vs. Floor Elevation, 
V Zone, 50'x30', 1 Story, Timber Pile Foundation 
$170,000 
$175,000 
$180,000 
$185,000 
$190,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Final Building Cost 
Condition V-1 
Condition V-2 
Condition V-3 
Condition V-4 
Condition V-5 
Condition V-6 
Condition V-7 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 
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Similar analyses were performed for pile foundations across all flood hazard zones and building 
sizes. The foundation cost trends for the 1,500 sf, 1-story building cases are typical, and are 
shown in Table 8. 
TABLE 8. Timber Pile Foundation Costs, 50x30, 1-Story Building 
Flood Flood Condition 
Hazard 
Zone 
Floor 
Elevation 
1 2 3 4 5 6 7 
BFE $12,979 $13,448 $14,082 $14,633 $15,184   
BFE + 1 ft $13,255 $13,723 $14,357 $14,909 $15,460   
BFE + 2 ft $13,530 $13,999 $14,633 $15,184 $15,735   
BFE + 3 ft $13,806 $14,275 $14,909 $15,460 $16,011   
A Zone 
BFE + 4 ft $14,082 $14,550 $15,184 $15,735 $16,287   
BFE $13,048 $13,406 $13,792 $14,213    
BFE + 1 ft $13,324 $13,682 $14,068 $15,221    
BFE + 2 ft $13,599 $13,957 $14,868 $16,183    
BFE + 3 ft $13,875 $14,233 $15,841 $17,107    
Coastal 
A Zone 
BFE + 4 ft $14,150 $14,509 $16,775 $18,000    
BFE $13,930 $14,839 $15,617 $16,955 $19,110 $20,413 $21,788 
BFE + 1 ft $14,507 $15,816 $16,552 $17,845 $19,933 $21,205 $22,551 
BFE + 2 ft $15,494 $16,753 $17,453 $18,707 $20,736 $21,981 $23,300 
BFE + 3 ft $16,439 $17,656 $18,325 $19,545 $21,521 $22,742 $24,349 
V Zone 
BFE + 4 ft $17,350 $18,530 $19,171 $20,362 $22,291 $23,488 $25,405 
 Not Applicable, as only five A zone conditions and four Coastal A zone conditions are defined in this study (see Table 4 and 
Figure 3 in Section 4.2). 

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The V zone pile foundation cost data in Table 8 show that the foundation cost increases 
as the V zone conditions get more severe, i.e., from the landward V zone condition (V-1) to the 
most seaward condition (V-7). Foundation cost also increases with freeboard (from the BFE to 
BFE + 4 ft). These same trends are apparent for all other V zone pile foundation combinations (4 
building sizes, timber and concrete piles). 
The Coastal A zone pile foundation cost data in Table 8 show that the foundation cost 
also increases from the landward Coastal A zone condition (CA-1) to the most seaward condition 
(CA-4), and with increasing freeboard (from BFE to BFE + 4 ft). The trends are not as uniform 
as in the V zone, however. The Coastal A zone pile foundation cost trends reflect the pile 
embedment trends shown in Figure 5: embedments and costs in the more severe Coastal A zone 
conditions tend to behave similar to V zone trends, while embedments and costs in the landward 
part of the Coastal A zone are similar to A zone trends (uniform embedment across conditions, 
and increasing foundation costs due to freeboard). 
The A zone pile foundation cost data in Table 8 show that the foundation cost also 
increases from the shallowest A zone condition (A-1) to the deepest condition (A-5), and with 
increasing freeboard (from BFE to BFE + 4 ft). The trends are more consistent for A zones than 
other flood hazard zones, since the lateral loads are less and the embedment requirements tend to 
be uniform across different flood conditions. 
6.3.2. Masonry Pier Foundations 
Unit costs for the masonry piers are given in Table 9. Pier foundation cost calculations 
assumed all piers would be spaced 10 feet apart and constructed in a typical fashion  i.e., 
16-inch square masonry block piers, reinforced and filled with concrete, extending 30 inches into 
the ground and supported on 8 inch thick, 3-foot square reinforced concrete footings  even 
though calculations showed most of these designs were not sufficient to resist the anticipated 
lateral loads and expected scour under V zone and Coastal A zone conditions described in Table 
4.22 The pier foundations described in this report (and commonly constructed) are adequate only 
for A zones not subject to waves and scour. 
TABLE 9. 2003 Unit Costs for Masonry Pier Foundations 
16 square Cost ($/lf) Footing Cost ($ each) 
masonry pier, 
reinforced and 
filled, set 30 into 
ground and atop 
8 thick 
reinforced 
concrete footing 
$18.12 
$64.00 
Calculated masonry pier foundation costs for the 1,500 sf, 1-story A zone building are 
shown in Figure 10. These costs translate into a range of approximately $2/sf to $6/sf for the 
22 This assumption was used to preserve a typical pier foundation alternative (consistent with typical construction 
practice), and calculated costs represent a lower bound for actual pier foundation costs. In the case of an actual 
building design, footing sizes and embedment depths would have to be increased considerably, and column crosssections 
would have to be increased for conditions V-5, V-6 and V-7, making the actual costs comparable to (or 
even in excess of) pile foundation costs. 
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building. By adding the foundation costs to the base-building-minus-foundation cost ($96,153 
from Table 6), the final building costs can be obtained. These results are shown in Figure 11. 
Similar analyses were performed for masonry pier foundations across all flood hazard zones and 
building sizes. The foundation cost trends for the 1,500 sf, 1-story building cases are typical, and 
are shown in Table 10. Note that since the pier embedment depth was fixed at 30 inches for all 
cases, pier foundation costs for condition CA-4 are identical to condition CA-3, costs for 
condition V-2 are identical to condition V-1, costs for condition V-4 are identical to V-3, and 
costs for conditions V-6 and V-7 are identical to V-5 (pier costs vary only with pier height above 
grade). Also, given the similar stillwater flood depth (e.g., CA-1 vs. A-1, CA-3 vs. A-2, V-5 vs. 
A-3), Coastal A zone and V zone pier foundation costs are higher than A zones costs due to the 
fact that taller piers are required to elevate above the wave crest. 
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FIGURE 10. Masonry Pier Foundation Cost vs. Floor Elevation, 
A Zone, 50'x30', 1 Story (Bldg. cost without foundation = $96,153) 
$3,000 
$4,000 
$5,000 
$6,000 
$7,000 
$8,000 
$9,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Pier Foundation Cost
Condition A-1 
Condition A-2 
Condition A-3 
Condition A-4 
Condition A-5 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 
FIGURE 11. Final Building Cost vs. Floor Elevation, 
A Zone, 50'x30', 1 Story, Masonry Pier Foundation 
$98,000 
$100,000 
$102,000 
$104,000 
$106,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Final Building Cost 
Condition A-1 
Condition A-2 
Condition A-3 
Condition A-4 
Condition A-5 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 

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TABLE 10. Masonry Pier Foundation Costs, 50x30, 1-Story Building 
Flood Flood Condition 
Hazard 
Zone 
Floor 
Elevation 
1 2 3 4 5 6 7 
BFE $3,167 $3,906 $4,906 $5,776 $6,646   
BFE + 1 ft $3,602 $4,341 $5,341 $6,211 $7,081   
BFE + 2 ft $4,037 $4,776 $5,776 $6,646 $7,516   
BFE + 3 ft $4,471 $5,211 $6,211 $7,081 $7,950   
A Zone 
BFE + 4 ft $4,906 $5,646 $6,646 $7,516 $8,385   
BFE $3,928 $4,493 $5,102 $5,102    
BFE + 1 ft $4,362 $4,928 $5,537 $5,537    
BFE + 2 ft $4,797 $5,363 $5,972 $5,972    
BFE + 3 ft $5,232 $5,798 $6,406 $6,406    
Coastal 
A 
Zone* 
BFE + 4 ft $5,667 $6,232 $6,841 $6,841    
BFE $5,320 $5,320 $6,059 $6,059 $6,929 $6,929 $6,929 
BFE + 1 ft $5,755 $5,755 $6,494 $6,494 $7,364 $7,364 $7,364 
BFE + 2 ft $6,189 $6,189 $6,929 $6,929 $7,799 $7,799 $7,799 
BFE + 3 ft $6,624 $6,624 $7,364 $7,364 $8,233 $8,233 $8,233 
V 
Zone* 
BFE + 4 ft $7,059 $7,059 $7,799 $7,799 $8,668 $8,668 $8,668 
 Not Applicable, as only five A zone conditions and four Coastal A zone conditions are defined in this study (see Section 4.2). 
* Masonry pier foundation costs for Coastal A zone and V zone are based on typical construction practices, not based on designs 
required to resist the loads and conditions stipulated in Table 4. Properly designed pier foundations under those scenarios would 
be larger, deeper and more expensive. The Coastal A zone and V zone pier foundation costs shown above -- while reflective of 
common construction practice -- are lower than the cost of an adequately designed pier foundation. 
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As was the case with pile foundations, the A zone pier foundation cost data in Table 10 
show that the foundation cost increases as the A zone conditions get more severe, i.e., from the 
landward A zone condition (A-1) to the most seaward condition (A-5). Foundation costs also 
increase with freeboard (from the BFE to BFE + 4 ft). 
The Coastal A zone pier foundation costs and V zone pier foundation costs also increase 
from the landward Coastal A zone condition (CA-1) to the most seaward condition (CA-4), from 
the most landward V zone condition (V-1) to the most seaward condition (V-7), and with 
increasing freeboard (from BFE to BFE + 4 ft). 
6.3.3. Wall Foundations 
Unit costs for the masonry wall (crawlspace) foundations are based on the Marshall & Swift 
(2003) standard foundation and are given in Table 11. Wall foundation cost calculations assumed 
walls would be 8-inch or 12-inch concrete masonry block, supported by reinforced concrete 
footings, and reflective of typical construction practice. The foundations would also include 
masonry piers to support the interiors of the buildings (i.e., the perimeter wall would replace the 
exterior piers). Even though design calculations showed these designs were not sufficient to 
resist the anticipated lateral loads and expected scour under Coastal A zone conditions described 
in Table 4, the Coastal A zone cost calculations were made23. The wall foundations described in 
this report (and commonly constructed) are adequate only for those for A zones not subject to 
waves and scour. 
TABLE 11. 2003 Unit Costs for Masonry Wall (Crawlspace) Foundations with Interior Piers 
Unit Cost ($/sf) 
Wall Construction 1-story, 
1,500 sf 
2-story, 
3,000 sf 
1-story, 
2,400 sf 
2-story, 
4,800 sf 
Cost for initial 
8-in concrete masonry wall on construction $2.65 $2.09 $2.65 $2.09 
reinforced concrete footing 
(extends from footing to 24-in 
above grade). 
Cost to raise 
foundation 1 ft $1.05 $0.53 $0.86 $0.43 
Cost for initial 
12-in concrete masonry wall on construction $3.98 $3.14 $3.98 $3.14 
reinforced concrete footing 
(extends from footing to 24-in 
above grade). Cost to raise 
foundation 1 ft $1.16 $0.58 $0.94 $0.47 
Calculated masonry wall foundation costs for the 1,500 sf, 1-story A zone building are 
shown in Figure 12. These costs translate into a range of approximately $3/sf to $15/sf for the 
building. By adding the foundation costs to the base-building-minus-foundation cost ($96,153 
23 This assumption was used to preserve a typical crawlspace foundation alternative (consistent with typical 
construction practice). In the case of an actual building design, footing sizes and embedment depths would have to 
be increased considerably, and column cross-sections would have to be increased for Coastal A zone conditions, 
making the actual costs comparable to (or even in excess of) pile foundation costs. 
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from Table 6), the final building costs can be obtained. These results are shown in Figure 13. 
Similar analyses were performed for masonry wall foundations in Coastal A zones. The 
foundation cost trends for the 1,500 sf, 1-story building cases are typical, and are shown in Table 
12. Note that since the wall embedment depth was constant for all cases, wall foundation costs 
for condition CA-4 are identical to condition CA-3 (wall costs vary only with pier height above 
grade). 
6.3.4. Elevation on Fill (Concrete Slab) 
The fill foundation costs (see Table 13) were calculated using the assumptions described 
in Section 5.4, with a June 2003 unit fill cost of $11.31/cy installed. Building costs for buildings 
elevated on fill were predicated on the assumption that the cost of a concrete slab would be 
approximately equal to the cost of a wood floor system (which is used in conjunction with all 
other foundations). Thus, the final building cost is the sum of the without-foundation cost shown 
in Table 6 and the fill costs in Table 13. 

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FIGURE 12. 8-in Masonry Wall (Crawlspace, with interior piers) Foundation Cost vs. Floor 
Elevation, 
A Zone, 50'x30', 1 Story (Bldg. cost without foundation = $96,153) 
$3,000 
$6,000 
$9,000 
$12,000 
$15,000 
$18,000 
$21,000 
$24,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Wall Foundation Cost 
Condition A-1 
Condition A-2 
Condition A-3 
Condition A-4 
Condition A-5 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 
FIGURE 13. Final Building Cost vs. Floor Elevation, 
A Zone, 50'x30', 1 Story, 8-in Masonry Wall (with interior piers) Foundation 
$100,000 
$105,000 
$110,000 
$115,000 
$120,000 
$125,000 
BFE 1 2 3 4 
Floor Elevation (ft above BFE) 
Final Building Cost
Condition A-1 
Condition A-2 
Condition A-3 
Condition A-4 
Condition A-5 
NOTE: See Table 4 and Figure 3 in Section 4.2 for a description of flood conditions. 

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TABLE 12. 8-in Masonry Wall Foundation Costs, 50x30, 1-Story Building 
Flood Flood Condition 
Hazard 
Zone 
Floor 
Elevation 
1 2 3 4 5 6 7 
BFE $3,972 $6,649 $10,272 $13,422 $16,572   
BFE + 1 ft $5,547 $8,224 $11,847 $14,997 $18,147   
BFE + 2 ft $7,122 $9,799 $13,422 $16,572 $19,722   
BFE + 3 ft $8,697 $11,375 $14,997 $18,147 $21,297   
A Zone 
BFE + 4 ft $10,272 $12,950 $16,572 $19,722 $22,872   
BFE $6,731 $8,779 $10,984 $10,984    
BFE + 1 ft $8,306 $10,354 $12,559 $12,559    
BFE + 2 ft $9,881 $11,929 $14,134 $14,134    
BFE + 3 ft $11,456 $13,504 $15,709 $15,709    
Coastal 
A 
Zone* 
BFE + 4 ft $13,031 $15,079 $17,284 $17,284    
BFE ** ** ** ** ** ** ** 
BFE + 1 ft ** ** ** ** ** ** ** 
BFE + 2 ft ** ** ** ** ** ** ** 
BFE + 3 ft ** ** ** ** ** ** ** 
V Zone 
BFE + 4 ft ** ** ** ** ** ** ** 
 Not Applicable, as only five A zone conditions and four Coastal A zone conditions are defined in this study (see Section 4.2). 
* Masonry wall foundation costs for Coastal A zones are based on typical construction practices, not based on designs required to 
resist the loads and conditions stipulated in Table 4. Wall foundations under those scenarios would be larger, deeper and more 
expensive. The Coastal A zone wall foundation costs shown above -- while reflective of common construction practice -- are 
lower than the cost of an adequately designed wall foundation. 
** Wall foundations are not permitted in V zones
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TABLE 13. Fill Foundation Costs, 50x30 Building 
Flood Flood Condition 
Hazard 
Zone 
Floor 
Elevation 
1 2 3 4 5 6 7 
BFE $2,287 $5,974 $12,784 $20,665 $30,623   
BFE + 1 ft $4,328 $8,660 $16,480 $25,369 $36,456   
BFE + 2 ft $6,738 $11,766 $20,665 $30,623 $42,898   
BFE + 3 ft $9,546 $15,321 $25,369 $36,456 $49,981   
A Zone 
BFE + 4 ft $12,784 $19,356 $30,623 $42,898 $57,732   
BFE $3,574 $5,606 $7,950 $7,950    
BFE + 1 ft $5,851 $8,231 $10,948 $10,948    
BFE + 2 ft $8,516 $11,272 $14,388 $14,388    
BFE + 3 ft $11,600 $14,758 $18,301 $18,301    
Coastal 
A 
Zone* 
BFE + 4 ft $15,132 $18,719 $22,716 $22,716    
BFE ** ** ** ** ** ** ** 
BFE + 1 ft ** ** ** ** ** ** ** 
BFE + 2 ft ** ** ** ** ** ** ** 
BFE + 3 ft ** ** ** ** ** ** ** 
V Zone 
BFE + 4 ft ** ** ** ** ** ** ** 
 Not Applicable, as only five A zone conditions and four Coastal A zone conditions are defined in this study (see Section 4.2). 
* Fill foundation in Coastal A zones will be subject to scour and erosion, and are not recommended. 
** Elevation on fill is not permitted in V zones
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6.4. Freeboard and Foundation Cost Comparisons 
6.4.1. Pile Foundation Cost 
review of all of the pile foundation cost calculations (all flood zones, flood conditions, building 
types and pile materials) shows that the effects of increasing flood hazards and increasing 
freeboard are most pronounced in V zones, followed by Coastal A zones, then A zones. The 
approximate percent foundation cost increases are summarized in Table 14, broken down into 
hazard effects (i.e., flood depth, wave height, flow velocity and scour) and freeboard effects. 
TABLE 14: Approximate Percent Increase in Pile Foundation Cost Due to Increasing Flood Severity and Freeboard 
Flood Hazard Zone 
Scenario 
V Zone Coastal A Zone A Zone 
Hazard Effect on Pile 
Foundation Cost 
Hold Floor Elevation 
Constant, Move from Least 
Hazardous Condition to 
Most Hazardous Condition 
50% - 80% 
(V-1 to V-7) 
10% to 80% 
(CA-1 to CA-4) 
10% - 20% 
(A-1 to A-5) 
Freeboard Effect on Pile 
Foundation Cost 
Hold Flood Condition 
Constant, Add Freeboard 
20% to 50% 
(BFE to BFE + 4 ft) 
10% to 50% 
(BFE to BFE + 4 ft) 
5% to 15% 
(BFE to BFE + 4 ft) 
It should be noted that although some of the percentage increases in Table 14 are large, 
the costs of the pile foundations are small by comparison to the total building costs. Since the 
pile foundations represent approximately 5% to 15% of the total building cost, the cost impacts 
of increasing flood hazards on pile foundations are relatively modest (from less than 2% of the 
building cost to approximately 12% of the building cost). The cost impacts of freeboard for pile 
foundations are even less, averaging approximately 1% to 2% of the at-BFE building cost for 4 ft 
of added freeboard (approximately 0.25% to 0.5% per foot of freeboard). Based on this analysis, 
it is clear that hazard intensity has a greater impact on the foundation and building costs than 
does adding freeboard. 
For example, Table 6 shows the without-foundation cost for a 1,500 sf building is 
$157,931. Table 8 shows the timber pile foundation cost for this building elevated to the BFE on 
a pile foundation and subject to flood condition V-1 is $13,930, yielding a final building cost of 
$171,861 (also shown on Figure 9). The cost of adding four feet of freeboard is the difference 
between the foundation cost at the BFE and the foundation cost at the BFE + 4 ft (see Table 8: 
$17,350 - $13,930 = $3,420). The added foundation cost divided by the at-BFE building cost 
yields $3,420/$171,861 = 2.0% cost increase for four feet of freeboard. This result is typical for 
V zone pile foundations analyzed in this study, and higher than the typical A zone and Coastal A 
zone freeboard costs, which are approximately 1% for four feet of freeboard. 
6.4.2. Pier Foundation Cost 
Given the pier construction assumption stated previously, a review of all of the pier foundation 
cost calculations (all flood zones, flood conditions, building sizes) shows that the collective 
effects of increasing flood hazards (i.e., flood depths) and increasing freeboard are to add 
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between approximately 2% to 5% to the building cost24, based on the least severe flood condition 
for a building at the BFE. Approximately one-third of the increase is due to freeboard effects, 
and approximately two-thirds of the increase is due to flood hazard effects. The cost impact of 
freeboard for masonry pier foundations averages approximately 1% to 2% of the at-BFE building 
cost for 4 ft of added freeboard (approximately 0.25% to 0.5% per foot of freeboard). 
6.4.3. Wall Foundation Cost 
Given the wall construction assumption stated previously, a review of all of the wall foundation 
cost calculations (A and Coastal A flood zone conditions, all building sizes, 8-in and 12-in walls) 
shows that the effects of increasing flood hazards (i.e., flood depths) and increasing freeboard are 
to add between approximately 10% to 20% to the building cost25, based on the least severe flood 
condition for a building at the BFE. Approximately one-third of the increase is due to freeboard 
effects, and approximately two-thirds of the increase is due to flood hazard effects. The cost 
impact of freeboard for masonry wall (with interior pier) foundations averages approximately 3% 
to 6% of the at-BFE building cost for 4 ft of added freeboard (approximately 0.8% to 1.5% per 
foot of freeboard). 
6.4.4. Slab on Fill Foundation Cost 
Given the slab on fill construction assumption stated previously, a review of all of the foundation 
cost calculations (A and Coastal A flood zone conditions, all building sizes) shows that the 
effects of increasing flood hazards (i.e., flood depths) and increasing freeboard are to add 
between approximately 10% to 60% to the building cost, based on the least severe flood 
condition for a building at the BFE. Approximately one-tenth to one-fifth of the increase is due 
to freeboard effects, and approximately the remaining three- to four-fifths of the increase is due 
to flood hazard effects. The cost impact of freeboard for fill foundations averages approximately 
3% to 11% of the at-BFE building cost for 4 ft of added freeboard26. 
6.4.5. Foundation Cost Comparison 
A comparison of Tables 8, 10, 12 and 14 shows that, for A and Coastal A zones, pier 
foundations are generally the most cost effective, with the exception of slab-on-fill foundations 
where the height of the fill pad is low (less than two feet). The advantage of fill quickly 
disappears as the fill pad height increases. Figure 14 and Table 15 summarize the foundation cost 
trends for the 1-story, 1,500 sq ft A zone house, which are representative of other houses 
modeled in this study as well. 
For V zones, pier foundations are less expensive than pile foundations  but that may be 
due in part to the comparison of typical shallow pier embedment foundations versus pile 
foundations with the required embedment to resist all lateral forces and scour. As was stated 
24 The higher percentage, 5%, is associated with the 1-story, 1,500 sq ft house; the lower percentage, 2%, is 
associated with the 2-story, 4,800 sq ft house. 
25 The higher percentage, 20%, is associated with the 1-story, 1,500 sq ft house; the lower percentage, 10%, is 
associated with the 2-story, 4,800 sq ft house. 
26 The fill quantity and fill cost do not increase linearly with freeboard (the cost increase in percentage terms is 
lowest for one foot of freeboard, and increases for each additional foot of freeboard), but on average, add 0.8% to 
3.0 % per foot of freeboard to the at-BFE building cost. 
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previously, typical pier foundations are not recommended in V zones and Coastal A zones where 
scour and large lateral loads will be present during the base flood. 
Data in Table 15 and other data in Chapter 7 demonstrate that the incremental costs of 
replacing minimally compliant A zone foundations (such as slab-on-fill and crawlspace 
foundations) with pier foundations or pile foundations are relatively small, generally less than 
5% to 10% of the cost of the building. In Coastal A zones, post-storm field studies have shown 
that minimally compliant A zone foundations often fail, and this replacement is warranted. In A 
zones outside coastal areas, NFIP compliant slab-on-fill and crawlspace foundations are 
generally adequate, and the incremental cost of changing to a pile foundation is not likely 
justified. However, changing to a pier foundation is probably justified, especially for flood 
depths more than a few feet above grade. Analyses in Chapter 7 will examine this topic further. 
Figure 14. Foundation Cost Summary, A Zone, 50' x 30', 1-story, Floor at BFE 
$0 
$5,000 
$10,000 
$15,000 
$20,000 
$25,000 
$30,000 
$35,000 
A-1 A-2 A-3 A-4 A-5 
Flood Condition 
Foundationn Cost 
Slab-on-Fill 
8" Masonry Wall 
Masonry Pier 
Timber Pile 
Table 15. Foundation Cost Comparison, A Zone, 1,500 sq ft, 1-Story House 
Foundation Cost ($/sq ft) 
Foundation Type Floor at BFE, 2 ft above 
Grade 
Floor at BFE, 6 ft above 
Grade 
Floor at BFE, 10 ft above 
Grade 
Slab-on-Fill 1.52 8.52 20.42 
Masonry Pier 2.11 3.27 4.43 
8 Masonry Wall 2.65 6.85 11.05 
Timber Pile 8.65 9.39 10.12 
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7. BENEFIT-COST ANALYSES 
Benefit-cost models in FEMAs BCA Toolkit CD-ROM Version 2.0 (FEMA 2005e) 
were investigated for use by this study. The models are employed by many for the analysis of 
publicly funded hazard mitigation projects, and consistency with those analysis procedures is 
desirable for the 1-and 2-story residential buildings considered by this study. 
After a preliminary review of each of the four flood models available in the BCA Toolkit 
(Riverine A zone, Limited Data; Riverine A zone, Full Data; Coastal A zone; V zone), it was 
determined that: 
 The Riverine A zone Limited Data model was not appropriate for this study since 
the model relies on observed historical damages and does not allow detailed user 
inputs for flood hazard and building parameters. 
 Even though the Riverine A zone Full Data model allows detailed user inputs, it 
requires specification of the 10-yr, 50-yr, 100-yr and 500-yr flood discharges and 
water levels of the same return periods. The model could not be used in this study 
since building damage under various flood elevations is being investigated, 
without regard to flood discharge. 
 The Coastal A zone and V zone models allow detailed user inputs, specify the 
flood hazard only in terms of flood elevation, and could potentially be used in this 
study. The Coastal A zone model can also be used in Riverine A zones. 
The V zone model was investigated in detail and rejected for use in this study.27 The 
Coastal A zone model was investigated in detail, was found not to have the problems contained 
in the V zone model, and was modified for use in V zones. Thus, the Coastal A zone model, or a 
modification to it, was used for all of the benefit-cost analyses (V zone, Coastal A zone, A zone) 
in this study. 
Using the Coastal A zone model(s), this study determined the maximum justified cost of 
mitigation, i.e., freeboard and/or foundation changes at the time of initial construction -- 
expressed as a percentage of initial construction cost -- that would yield a B/C greater than or 
equal to 1.0. This approach generalizes the results and avoids problems associated with specific 
buildings and their costs at specific points in time. 
27 As part of the model review, the same inputs were used in the V zone model and the Coastal A zone model, which 
should have resulted in identical (or very similar) benefit-cost ratios. There were considerable differences in the 
results, with the V zone model predicting B/Cs that were 6% to 40% higher than the Coastal A zone models for 
several scenarios run. A detailed evaluation of the V-zone model revealed errors. For example, the model calculated 
annual probabilities of flood levels (which are used to calculate annualized flood damages) incorrectly. In addition, 
the evaluation determined that the V zone model did not perform calculations with user-defined inputs for some 
parameters (ignoring the user inputs and using the model default values instead). The Coastal A zone model was 
evaluated in detail and found not to repeat the V zone model errors. Model errors were documented and submitted to 
FEMAs BCA contractor in September 2005. Version 3.0 of FEMAs BCA Toolkit was released in July 2006, and 
reportedly corrects the errors found in Version 2.0. 
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The Evaluation of the National Flood Insurance Program 
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7.1. Benefit-Cost Model Description 
The Coastal A zone model used in this study is documented in FEMA (2005f). The 
model inputs (which may be model-default values or user-defined) can be broken down into the 
following categories: 
 Project Description 
 Discount Rate 
 Building Data (e.g., building type and number of stories; footprint area and total 
floor area; elevation of the lowest floor; replacement value; level of damage that 
will result in building demolition, etc.) 
 Contents Data (e.g., value of contents) 
 Displacement Costs (e.g., one-time costs; temporary rental costs; other ongoing 
displacement costs) 
 Value of Public/Non-Profit Services Housed in the Building 
 Lost Rent and Business Income 
 Mitigation Project Information (e.g., type of mitigation; cost of mitigation; useful 
life of mitigation project; relocation time and costs during mitigation project) 
 Flood Elevation Data (e.g., 1-yr, 10-yr, 50-yr, 100-yr and 500-yr flood elevations; 
expected annual number of floods at 1-ft increments from 2-ft below the lowest 
floor to 8-ft above the lowest floor) 
 Depth-Damage Functions (building damage % versus depth of flooding relative to 
the lowest floor; separate building and contents damage curves, which vary by 
building type and number of stories) 
 Displacement Time and Costs (period of time out of the building versus flood 
depth above the floor, and associated costs) 
The model calculates expected annual damages and costs, with and without the 
mitigation project, calculates the annual benefits of the mitigation project, converts those benefits 
to a present value, compares the present value of the project benefits to the initial project cost, 
and computes a B/C ratio. This ratio serves as the basis for comparing foundation and freeboard 
changes in this study. 
7.2. Model Inputs Used in this Study 
Inputs used in this study are described below and in Table 16.
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TABLE 16: Input Parameters Used in this Study 
Input Parameter Values Used in this Study 
Parameter Coastal A Zone Model 
Default 
V Zone Coastal A Zone A Zone 
Discount Rate 
FEMA Guidance (2004 and 
other) mandates 7.0%1 per 
OMB Circular A-94, 
Appendix C. 
3.0%, 5.0%, 7.0%, 
9.0% 
3.0%, 5.0%, 7.0%, 
9.0% 
3.0%, 5.0%, 7.0%, 
9.0% 
Project Useful Life 30 years2 30 years 30 years 30 years 
Building Data 
Building Type 
Number of Stories 
Building Size 
Building Cost 
Lowest Floor 
Elevation 
 
 
 
 
 
residence 
1 and 2 
1,500 to 4,800 sf 
* 
BFE, BFE+1, 
BFE+2, BFE+3, 
BFE+4 
residence 
1 and 2 
1,500 to 4,800 sf 
* 
BFE, BFE+1, 
BFE+2, BFE+3, 
BFE+4 
residence 
1 and 2 
1,500 to 4,800 sf 
* 
BFE, BFE+1, 
BFE+2, BFE+3, 
BFE+4 
Building Damage 
that Results in 
Demolition 
50%3 50% 50% 50% 
Value of Contents 30%4 30% 30% 30% 
Public/Non-Profit 
Services Housed in 
Building 
 none none none 
Lost Rent and 
Business Income  none none none 
Mitigation Project 
Project Type 
Initial Project Cost 
Annual Costs to 
Maintain Project 
Relocation Time 
Relocation Costs 
 
 
 
 
 
Freeboard5 
% of Building Cost6 
none7 
none 
none 
Freeboard5 
% of Building Cost6 
none7 
none 
none 
Freeboard5 
% of Building Cost6 
none7 
none 
none 
Flood Elevation Data From Flood Insurance Study 
(FIS) 
Range of BFEs (12 ft 
to 20 ft msl), with nyr 
wave crest 
elevations calculated 
using HAZUS flood 
elevation ratios9 
Range of BFEs (12 ft 
to 20 ft msl), with nyr 
wave crest 
elevations calculated 
using HAZUS flood 
elevation ratios9 
Range of FHFs (25 
to 150), with n-yr 
flood elevations 
calculated using 
method by Wilbert 
Thomas8 
Depth-Damage 
Functions 
Default functions (buildings 
and contents) from FIA for 
different flood zones and 
building types 
FIA V zone function, 
no obstructions10 
FIA V zone function, 
no obstructions10 
FIA A zone 
functions for 1- and 
2-story, no basement 
Displacement Time 
and Costs 
Default time based on flood 
depth above lowest floor, 
costs associated with 
displacement 
none11 none11 none11 
(Table Notes , *, and 1 - 11 are on next page) 
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The Evaluation of the National Flood Insurance Program 
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Notes for Table 16 
 User defined 
* Building costs were calculated in this study (see Chapter 7) using Marshall & Swift (2003) and the foundations designed for 
various flood conditions (see Section 7). The building cost input into model here is the cost for a new building, elevated to the 
BFE on a minimally compliant NFIP foundation. 
1. January 2006 Appendix C to OMB Circular A-94 gives nominal rate = 5.2%, real rate = 3.0%. 
2. FEMA (2004), section 4.14 uses 30 years as the useful life of a residential elevation project. 
3. FEMA (2004), section 2.4.5 uses 50% damage as the threshold for demolition. 
4. FEMA (2004), section 2.4.6 uses 30% as the ratio of contents to structure value. 
5. Mitigation Project in this study means the addition of freeboard or the use of a different foundation at the time of initial 
construction. 
6. As used in this study, initial project cost is the additional cost to provide freeboard and/or a different foundation at the time 
of initial construction. The reference from which additional costs are calculated is the cost to elevate the home to the BFE on a 
minimally compliant NFIP foundation. 
7. There are assumed to be no annual costs to maintain the initial freeboard or foundation change. However, in a study of this 
type, this field could be used to insert other annual costs or savings, such as reductions in flood insurance premiums. 
8. Thomas (2003) developed a procedure to calculate n-year flood depths in streams, given only the 100-yr flood depth. The 
following FHFs were used in the analysis: 25, 50, 75, 100 and 150. Thomas (personal communication, July 17, 2006) 
confirmed that the range was reasonable -- a review of 100 streams in one state showed FHFs between 10 and 100. Since B/C 
decreases as FHF increases, using the range 25 to 150 will result in conservative B/C values. 
9. 10-yr, 50-yr and 500-yr flood Elevation Ratios were developed for the HAZUS Flood Model (EQE 2000, Section 5.2.2.2). The 
relationship was extended to the 1-yr level in this study. 
10. EQE (2000, Section 8.2.3) determined that the V zone depth-damage functions provide a better fit to actual damage in 
Coastal A zones. 
11. Sensitivity tests were run to examine the effects of including monthly displacement costs (as a percentage of initial 
construction cost) and using BCA model default displacement times. 
__________________ 
7.2.1. Discount Rate 
FEMAs Benefit-Cost guidance (FEMA 2004, pages 3, 7, 14; FEMA 2005f, page 6-5) 
states clearly that a discount rate of 7.0% should be used for FEMA-funded hazard mitigation 
projects, and states that this rate is mandated by the Office of Management and Budget (OMB).28 
Inasmuch as different users of this study may look at the results from different perspectives, and 
may require analyses at rates other than the OMB discount rate, the cost-benefit analyses in this 
study were made using a baseline rate of 7.0%, and sensitivity analyses were run for 3.0%, 5.0% 
and 9.0%. The 5.0% rate corresponds roughly to the current OMB nominal discount rate (the rate 
paid by 30-year Treasury bonds), the 3.0% rate corresponds to the current OMB real discount 
rate, and the 9.0% rate corresponds to higher rates that consumers may see at present. 
However, extension of this studys results to other rates is not difficult  the B/C ratio for 
a project with a 7.0% discount rate can be converted to a B/C ratio at another rate, by multiplying 
the 7.0% B/C by the ratio of the present value coefficient for the new rate to the present value 
coefficient for 7.0%29.. For example, if a project has a B/C = 2.00 at a discount rate of 7.0% and 
useful life of 30 years, the same project would have a B/C = 2.48 at a discount rate of 5.0% and a 
useful life of 30 years and (2.48 = 2.00 x [15.37/12.41]). 
28 OMB publishes, on an annual basis, nominal and real discount rates to be used in the evaluation of federal 
programs and expenditures. The 2006 values are 5.2% and 3.0%, respectively (OMB 2006). 
29 Values of these present value coefficients have been tabulated and are contained in numerous documents, and are 
included in Table 17 
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The Evaluation of the National Flood Insurance Program 
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TABLE 17. Present Value Coefficients vs. Discount Rate and Project Useful Life* (Source: FEMA 2005f, page 9-10) 
Useful Discount Rate 
Life 
(years) 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 
1 0.99 0.98 0.97 0.96 0.95 0.94 0.93 0.93 0.92 0.91 
2 1.97 1.94 1.91 1.89 1.86 18.3 1.81 1.78 1.76 1.74 
3 2.94 2.88 2.83 2.78 2.72 2.67 2.62 2.58 2.53 2.49 
4 3.90 3.81 3.72 3.63 3.55 3.47 3.39 3.31 3.24 3.17 
5 4.85 4.71 4.58 4.45 4.33 4.21 4.10 3.99 3.89 3.79 
6 5.80 5.60 5.42 5.24 5.08 4.92 4.77 4.62 4.49 4.36 
7 6.73 6.47 6.23 6.00 5.79 5.58 5.39 5.21 5.03 4.87 
8 7.65 7.33 7.02 6.73 6.46 6.21 5.97 5.75 5.53 5.33 
9 8.57 8.16 7.79 7.44 7.11 6.80 6.52 6.25 6.00 5.76 
10 9.47 8.98 8.53 8.11 7.72 7.36 7.02 6.71 6.42 6.14 
15 13.87 12.85 11.94 11.12 10.38 9.71 9.11 8.56 8.06 7.61 
20 18.05 16.35 14.88 13.59 12.46 11.47 10.59 9.82 9.13 8.51 
25 22.02 19.52 17.41 15.62 14.09 12.78 11.65 10.67 9.82 9.08 
30 25.81 22.40 19.60 17.29 15.37 13.76 12.41 11.26 10.27 9.43 
40 32.83 27.36 23.11 19.79 17.16 15.05 13.33 11.92 10.76 9.78 
50 39.20 31.42 25.73 21.48 18.26 15.76 13.80 12.23 10.96 9.91 
60 44.96 34.76 27.68 22.62 18.93 16.16 14.04 12.38 11.05 9.97 
70 50.17 37.50 29.12 23.39 19.34 16.38 14.16 12.44 11.08 9.99 
80 54.89 39.74 30.20 23.92 19.60 16.51 14.22 12.47 11.10 10.00 
90 59.16 41.59 31.00 24.27 19.75 16.58 14.25 12.49 11.11 10.00 
100 63.03 43.10 31.60 24.50 19.85 16.62 14.27 12.49 11.11 10.00 
1000 100.00 50.00 33.33 25.00 20.00 16.67 14.29 12.50 11.11 10.00 
* Shaded cells indicate the Discount Rates and Useful Life used by this study. The present value coefficient corresponding to a 
discount rate of 7.0%, and a useful life of 30 years (12.41) was used for this studys baseline B/C calculations. 

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The Evaluation of the National Flood Insurance Program 
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7.2.2. Mitigation Project Description 
As used in this study, mitigation project refers to the addition of freeboard or the use of a 
different foundation at the time of initial construction. The study considered the affects of 
adding between one and four feet of freeboard at the time of initial construction. The study 
considered the affects of replacing of A zone type foundations with V zone type foundations, and 
replacing pier foundations with pile foundations. 
7.2.3. Useful Life 
The useful life of the mitigation project used in this study is 30 years, as suggested by 
FEMA (2004) guidance. This studys results can be extended to other useful lives  the B/C 
ratio for a project with a 30-year life can be converted to a B/C ratio for another useful life by 
multiplying the 30-year life B/C by the ratio of the present value coefficient for the new useful 
life to the present value coefficient for the 30-year life (see Table 17). For example, if a project 
has a B/C = 2.00 at a discount rate of 7.0% and useful life of 30 years, the same project would 
have a B/C = 2.22 with a useful life of 50 years and a discount rate of 7.0% (2.22 = 2.00 x 
[13.80/12.41]). 
7.2.4. Building Damage that Results in Demolition 
This study used 50% damage30 as the threshold for building demolition, as called for by 
FEMA (2004). This value is also consistent with the percent damage which triggers substantial 
damage for a building in the SFHA. 
7.2.5. Contents Value 
This study used a contents-to-structure-value ratio of 30%, as suggested by FEMA (2004) 
guidance. In other words, this study assumed that the value of contents within a building would 
equal 30% of the construction cost of the building. 
7.2.6. Public/Non-Profit Use of the Buildings 
This study assumed the buildings being evaluated are private, residential structures, and 
that there would be no loss of public/non-profit services associated with damage to the buildings. 
7.2.7. Lost Rent and Business Income 
This study assumed the buildings were owner-occupied residential buildings, and no loss 
of rent or business income would result from damage to the buildings. 
7.2.8. Displacement Time and Costs 
Although FEMAs Coastal A zone model (and other models) include default estimates 
for the length of time that building occupants will be forced to leave the building in the event of 
30 Damage is expressed as a percentage of building value. 
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The Evaluation of the National Flood Insurance Program 
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flood damage (where the displacement time increases with increasing flood depth above the 
floor), this study assumed no displacement would occur. Thus, the results of this study are 
conservative  B/C values determined by this study will be low, when compared to B/C values 
which incorporate the displacement effects of flooding; higher mitigation costs at the time of 
initial construction will be justified than those determined by this study. However, sensitivity 
tests reported later in this chapter summarize the effect of displacement costs on B/C values. 
7.2.9. Flood Elevation Data 
This study is generic  it does not evaluate the benefits and costs of a particular 
mitigation project at a particular location, for which a Flood Insurance Study can be consulted to 
determine the 100-yr flood elevation and other return period flood elevations. Instead, the study 
was designed so its results would be applicable over a wide range of coastal and riverine base 
flood conditions (see Table 4 and Figure 3). The study design is contingent on two things being 
known:31 
 A relationship between the 100-yr flood (base flood) level and flood levels for 
other return periods, at any location within the SFHA (FEMAs model requires 
the user to input the 100-yr and other return period flood levels). 
 Some measure of the actual base flood level, or an additional relationship between 
the 100 year flood level and another return period flood level. 
Satisfying the first condition was accomplished using flood elevation frequency 
relationships developed previously, or developed during this study. The second condition was 
addressed by specification of a reasonable range of BFEs (for V zones and Coastal A zones), and 
Flood Hazard Factors (FHFs) for A zones. Note that as the coastal BFE or riverine FHF 
increases, the severity of the local flooding increases  high coastal BFEs and high riverine FHFs 
are associated with more hazardous flooding. 
V Zones and Coastal A Zones 
Generic relationships between the 100-yr flood elevations and other flood elevations 
were determined during development of the HAZUS Coastal Flood Model (EQE 2000). The 
relationships were determined through a selective review of coastal Flood Insurance Studies for 
the Atlantic, Gulf of Mexico and Pacific coasts. Although not exhaustive, the review examined 
coastal flood data from 46 coastal communities (27 Atlantic, 11 Gulf of Mexico, eight Pacific) 
on different shoreline exposures (31 open coast, 15 bay) with different flood conditions 
determining BFEs (38 wave height dominant, 8 wave runup dominant). The relationships -- 
called Flood Elevation Ratios, or the ratio between the n-yr flood elevation and the 100-yr 
flood elevation at the shoreline, were determined to be approximately constant on a nationwide 
basis, with small standard deviations. The coastal flood elevation ratios are shown in Table 18. 
31 The B/C ratio for a mitigation project depends on two factors related to the flood hazard: the base flood level at 
the site, and either the flood elevation frequency distribution (V zones and Coastal A zones) or Flood Hazard Factor 
(A zones). 
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Given the 100-year flood elevation, other flood elevations can be calculated. For 
example, if the 100-year flood elevation is 20.0 ft NGVD, the 1-year flood elevation will be 5.8 
ft (20.0 x 0.29), the 10-year flood elevation will be 12.8 ft (20.0 x 0.64), the 50-year flood 
elevation will be 17.6 ft (20.0 x 0.88), and the 500-year flood elevation will be 24.6 ft (20.0 x 
1.23). 
TABLE 18. Coastal Flood Elevation Ratios at the Shoreline 
Flood Return Period 
(years) 
Flood Elevation Ratio* 
(n-yr flood elevation / 100-yr flood elevation) 
1 0.29 
10 0.64 
50 0.88 
100 1.00 
500 1.23 
* The 10-yr, 50-yr and 500-yr ratios were taken from EQE (2000). The 1-yr 
ratio was determined by extrapolation during this study. 
For the purposes of this study, it is assumed that the same ratios will hold for 
depth-limited waves throughout the V zone and Coastal A zone. Sensitivity tests show the actual 
ratios throughout the V zone and Coastal A zone are within approximately 2% to 8% of the 
ratios at the shoreline, for typical ranges of BFEs in coastal areas (e.g., 12 ft to 20 ft) and for 
flood elevations that will enter into damage calculations (i.e., for flood levels 2 feet below the 
BFE and higher). 
The Coastal A zone model (as used for V zones and Coastal A zones) employed the ratios 
in Table 18 in the following manner. The 100-year flood elevation (BFE) was input as the 
elevation of the first (i.e., lowest) floor on the models Building Data input screen. This 
elevation was then transferred to the 100-year flood elevation cell on the Flood Hazard input 
screen, and the 1-yr, 10-yr, 50-yr and 500-yr flood elevations were calculated automatically 
using the ratios in Table 18.32 This flood elevation frequency data was then used by the model to 
determine the expected annual number of floods at 1-ft increments from two ft below the BFE to 
eight ft above the BFE. Freeboard was added later in 1-ft increments on the models Mitigation 
Project input screen, and the model was rerun each time freeboard was added. 
A Zones 
A simple determination of flood elevation ratios in non-coastal areas through a review of 
Flood Insurance Studies is not practical. Moreover, unlike coastal areas where all flood 
elevations at the shoreline are referenced to the same zero depth elevation (+/- mean sea level, 
msl), zero flood depth in riverine areas occurs at an infinite number of elevations above msl. 
32 The ratios will apply approximately at a site distant from the shoreline, since all wave heights considered in this 
study are depth-limited, both at the shoreline and away from the shoreline. 
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A procedure was developed by Thomas (2003) for this study, to estimate n-year flood 
depths in a stream, given the 100-year flood depth (see Appendix 3). The method is based on 
general relationships between the slope of the discharge-frequency curve and the relation 
between depth and discharge contained in the well-known Bulletin 17B (USGS 1982) and other 
sources. Application of this procedure shows that nationwide-average Flood Depth Ratios can 
be determined, and that those ratios are as given in Table 19. 
TABLE 19. Flood Depth Ratios for a Stream 
Flood Return Period 
(years) 
Flood Depth Ratio* 
(n-yr flood depth /100-yr flood depth, where 
depth is measured in the channel) 
1 0.18 
10 0.69 
50 0.91 
100 1.00 
500 1.21 
* Using the procedure developed by Thomas (2003). The 1-yr ratio is 
calculated at the 1.01-yr return period. 
The ratios in Table 19 must be used in conjunction with some estimate of the actual flood 
level or flood depth. However, unlike coastal floodplains where a reasonable range of stillwater 
elevations/BFEs can be estimated, BFEs in riverine floodplains vary too widely to identify a 
narrow range for use in this study. Instead of using the BFE to provide additional flood hazard 
specification in A zones, the Flood Hazard Factor will be used.33 
Using Equation 8 from Thomas (2003) in conjunction with the FHF definition, unique 
values of the 100-yr flood depth in the channel (d100) were determined for a range of typical 
FHFs for riverine A zones (see Figure 15 and Table 20). The 10-yr flood depth (d10) is equal to 
d100  FHF/10, or 0.69 d100. Channel flood depths at other return periods (dn) were calculated 
using the flood depth ratios in Table 19. All flood elevations En were referenced to the channel 
bottom elevation EC, and apply throughout the local floodplain. Since this study is generic in 
nature, EC was set equal to zero, and the flood depth ratios in Table 19 became flood elevation 
ratios, which were then used in the A zone B/C analyses (using the Coastal A zone model 
modified for A zones). 
7.2.10. Flood Depth-Damage Functions 
Flood depth-damage functions used in this analysis were those contained in the BCA 
Toolkit (FEMA 2005e). A zone damage functions were used for A zone buildings and their 
contents. V zone damage functions were used for V zone buildings and contents, as well as for 
33 The FHF for a stream reach is the difference between the 100-year and 10-year flood surface elevations rounded 
to the nearest one-half foot and multiplied by 10. For example, if the difference between the 100-year and the 
10-year water-surface elevations is 0.7 foot, the FHF is 5; if the difference is 1.4 feet, the FHF is 15; if the difference 
is 5.0 feet, the FHF is 50, etc. The FHF is a parameter that was computed and published in early FISs, but is no 
longer included in todays studies. However, the FHF calculation can still be made with available information. 
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Coastal A zone buildings and contents. The use of V zone damage functions for Coastal A zones 
was based on a study at Pensacola Beach (EQE, 2000, section 8.2.3) and on observed Coastal A 
zone building damages after recent hurricanes (FEMA 2005a). The damage functions used in this 
study are listed in Tables 21 and 22. 
TABLE 20. A Zone Flood Hazard Factors and Associated Flood Depths Used in this Study* 
Flood Hazard Factor 
(FHF) 
Difference Between 
100-yr and 10-yr Flood 
Depths in Channel (ft) 
[d100  d10] 
d100 (ft) Satisfying 
Thomas (2003) 
Equation 8 
Corresponding d10 (ft) 
25 2.5 8.0 5.5 
50 5.0 16.0 11.0 
75 7.5 24.0 16.5 
100 10.0 32.0 22.0 
150 15.0 48.0 33.0 
* d100 is measured relative to channel bottom EC and rounded to the nearest whole foot (see Figure 15). 
FIGURE 15. Sketch of Generic Riverine Floodplain and A Zone Flood Elevations Used in this Study 
d100 
SFHA 
EC 
E100 
dn 
En 
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The Evaluation of the National Flood Insurance Program 
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TABLE 21: V Zone and Coastal A Zone Depth-Damage Functions Used in this Study 
Flood Depth (ft)* One or More Stories, No Obstructions 
Building Damage (%) Contents Damage (%) 
< -2 0 0 
-2 10 0 
-1 12 6 
0 15 15 
1 23 23 
2 35 35 
3 50 50 
4 58 58 
5 63 63 
6 67 67 
7 70 70 
8 72 72 
> 8 78 78 
* Depth is measured from the bottom of the lowest horizontal structural member 
supporting the lowest floor. 
TABLE 22: A Zone Depth-Damage Functions Used in this Study 
Flood Depth (ft)* One-Story, No Basement Two-Story, No Basement 
Building Damage 
(%) 
Contents Damage 
(%) 
Building Damage 
(%) 
Contents Damage 
(%) 
< -2 0 0 0 0 
-2 0 0 0 0 
-1 0 0 0 0 
0 9 14 5 8 
1 14 21 9 14 
2 22 33 13 20 
3 27 41 18 27 
4 29 44 20 30 
5 30 45 22 33 
6 40 60 24 36 
7 43 65 26 39 
8 44 66 29 44 
> 8 45 68 33 50 
* Depth is measured from the top (walking surface) of the lowest floor. 

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The Evaluation of the National Flood Insurance Program 
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7.3. B/C Results 
7.3.1. V Zones and Coastal A Zones 
B/C values were calculated for new homes using the inputs shown in Table 16. Sample 
results are shown in Figures 16-19, where B/C ratios are plotted against the cost to elevate above 
the BFE (equal to 12.0 ft msl in this case), for different freeboard levels and different discount 
rates. To use the figures, select the BFE-Discount Rate combination desired, go to the 
appropriate figure and read across along the B/C = 1.0 line to see the additional cost justified for 
various freeboard levels. For example, if the BFE is 12 and the Discount Rate is 5.0%, use 
Figure 17  reading across one sees that it is worth spending another 5% at the time of initial 
construction to add 1 ft of freeboard, or another 9% to add 2 ft of freeboard, etc. The figures 
clearly show that the B/C ratio decreases as the discount rate increases, with all other inputs held 
constant. The B/C ratio also decreases as the BFE increases, with other inputs constant. 
All the V zone and Coastal A zone B/C calculations were tabulated and the B/Cs were 
determined for various combinations of freeboard, additional construction cost and discount rate. 
The data were then examined to identify the percentage of additional construction cost -- 
rounded to the nearest 1%34  that an owner would be justified in spending at the time of 
construction (B/C = 1.0) for each freeboard-BFE-discount rate combination. These results are 
shown in Table 23 and Figures 20-23 and are summarized below: 
 1 foot of freeboard above the BFE: spending 103% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 107% of the at-BFE 
building cost35. 
 2 feet of freeboard above the BFE: spending 104% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 111% of the at-BFE 
building cost. 
 3 feet of freeboard above the BFE: spending 105% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 113% of the at-BFE 
building cost. 
 4 feet of freeboard above the BFE: spending 106% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 114% of the at-BFE 
building cost. 
Note that the results cited above account only for damage to the buildings and their 
contents. Any additional costs resulting from the flooding (e.g., displacement costs such as 
temporary housing) and any cost savings as a result of adding freeboard (e.g., flood insurance 
premium reductions) justify spending even more money at the time of initial construction to 
reduce future flood damages. 
34 If the justified cost was less than 1.0% of the initial construction cost, it was rounded to the nearest 0.5% 
35 That is, for one foot of freeboard, spending an additional 3% above the at-BFE building cost at the time of 
construction is always justified for the scenarios studied herein. Spending up to 7% more than the at-BFE building 
cost for one foot of freeboard is justified for some BFE-discount rate combinations. 
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Figure 16. B/C Ratio versus Cost to Elevate with Freeboard (V Zone and Coastal A Zone, Piles or Piers, No 
Obstructions, BFE = 12 ft, DR = 3.0%, UL = 30 years, Contents @ 30%) 
0
1
2
3
4
5
6
7
8
9 
10 
11 
12 
13 
14 
15 
16
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Figure 17. B/C Ratio versus Cost to Elevate with Freeboard (V Zone and Coastal A Zone, Piles or Piers, No Obstructions, BFE = 12 
ft, DR = 5.0%, UL = 30 years, Contents @ 30%) 
0
1
2
3
4
5
6
7
8
9 
10 
11 
12 
13
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio 
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Figure 18. B/C Ratio versus Cost to Elevate with Freeboard (V Zone and Coastal A Zone, Piles or Piers, No Obstructions, BFE = 12 
ft, DR = 7.0%, UL = 30 years, Contents @ 30%) 
0
1
2
3
4
5
6
7
8
9 
10 
11
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 
Cost to Elevate Above BFE (% of construction cost at BFE) 
B/C Ratio 
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Figure 19. B/C Ratio versus Cost to Elevate with Freeboard (V Zone and Coastal A Zone, Piles or Piers, No Obstructions, BFE = 12 
ft, DR = 9.0%, UL = 30 years, Contents @ 30%) 
0
1
2
3
4
5
6
7
8
9
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 11% 12% 13% 14% 15% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio 
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Table 23. Percent* of Additional Construction Cost-Justified (B/C > 1.0) for Various Combinations of Freeboard, BFE 
and Discount Rate (V zone and Coastal A Zone, Pile and Pier Foundations, useful life =30 Years, Contents Value = 30% 
of Structure Value) 
Discount Rate = 3.0% 
BFE (ft msl) 
Freeboard (ft) 
12 14 16 18 20 
1 7 6 6 5 5 
2 11 10 9 8 8 
3 13 12 11 11 10 
4 14 14 13 12 12 
Discount Rate = 5.0% 
BFE (ft msl) 
Freeboard (ft) 
12 14 16 18 20 
1 6 5 4 4 4 
2 9 8 7 7 6 
3 11 10 9 8 8 
4 12 11 10 10 9 
Discount Rate = 7.0% 
BFE (ft msl) 
Freeboard (ft) 
12 14 16 18 20 
1 5 4 4 3 3 
2 7 6 6 5 5 
3 9 8 7 7 7 
4 10 9 8 8 8 
Discount Rate = 9.0% 
BFE (ft msl) 
Freeboard (ft) 
12 14 16 18 20 
1 4 3 3 3 3 
2 6 5 5 4 4 
3 7 7 6 6 5 
4 8 7 7 7 6 
* Percentages rounded to the nearest 1%. If the justified cost was less than 1.0% of the initial construction cost, it was rounded to 
the nearest 0.5%. Percentages account for flood damage to structure and contents only, and would be higher if displacement costs 
and flood insurance premium savings were included. 
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7.3.2. A Zones 
Similar calculations were made for A zones, except Flood Hazard Factors36 were used in 
lieu of BFEs, and two sets of calculations were made (for one story buildings and two-story 
buildings)37. B/C values were calculated for new homes using the inputs shown in Table 16. 
Sample results are shown in Figures 24-31, where B/C ratios are plotted against the cost to 
elevate above the BFE, for different flood hazard factors, different freeboard levels and different 
discount rates. The figures clearly show that the B/C ratio decreases as the discount rate 
increases, with all other inputs held constant. The B/C ratio decreases as the FHF increases, with 
all other inputs held constant. B/C ratios for two-story buildings are less than for corresponding 
one-story buildings due to lower depth-damage values (see Table 22). 
All the A zone B/C calculations were tabulated and the B/Cs were determined for various 
combinations of freeboard, additional construction cost and discount rate. The data were then 
examined to identify the percent of additional construction cost -- rounded to the nearest 1%38  
that an owner would be justified in spending at the time of construction (B/C = 1.0) for each 
freeboard-FHF-discount rate combination. These results are shown in Tables 24 and 25, and in 
Figures 32-39. 
In the one-story A zone cases studied, the calculations show: 
 1 foot of freeboard above the BFE: spending 100.5% of the base building (at BFE) 
cost is justified, and it may be worth spending up to 104% of the base building cost. If 
the FHF = 150, DR = 9.0% results are excluded, spending 101% of the base building 
cost is justified. 
 2 foot of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending up to 105% of the base building cost. If the 
FHF = 150, DR = 9.0% results are excluded, spending 102% of the base building cost 
is justified. 
 3 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 106% of the base building cost. 
 4 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 106% of the base building cost. If the FHF = 
150, DR = 9.0% results are excluded, spending 103% of the base building cost is 
justified. 
In the two-story A zone cases studied, the calculations show: 
 1 foot of freeboard above the BFE: spending 100.5% of the base building (at BFE) 
cost is justified, and it may be worth spending 102% of the base building cost. 
36 The FHF is the difference between the 100-year and 10-year flood surface elevations rounded to the nearest onehalf 
foot and multiplied by 10 
37 A zone depth-damage functions differ by number of building stories, V zone depth-damage functions do not. 
38 If the justified cost was less than 1.0% of the initial construction cost, it was rounded to the nearest 0.5% 
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 2 feet of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. 
 3 feet of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. If the FHF = 
150, DR = 9.0% results are excluded, spending 102% of the base building cost is 
justified. 
 4 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. 
The lower justified costs for two-story buildings are a result of the different A zone 
damage functions for one-story and two-story buildings. The same depth of flooding above the 
lowest floor leads to less damage (as a percent of the building and contents value) in a two-story 
building than a one story building. 
As in the case of the V zone and Coastal A zone, the results cited above account only for 
damage to the buildings and their contents. Any additional costs resulting from the flooding (e.g., 
displacement costs such as temporary housing) and any cost savings as a result of adding 
freeboard (e.g., flood insurance premium reductions) will make spending additional money at the 
time of initial construction justified. 
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Figure 24. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 1-story, No Basement, 
FHF = 25, DR = 3.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
5
6
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 
Figure 25. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 1-story, No Basement, 
FHF = 25, DR = 7.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
5
0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft
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Figure 26. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 1-story, No Basement, 
FHF = 50, DR = 3.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
5
6
0% 1% 2% 3% 4% 5% 6% 7% 8% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 
Figure 27. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 1-story, No Basement, 
FHF = 50, DR = 7.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
5
0% 1% 2% 3% 4% 5% 6% 7% 8% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Figure 28. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 2-story, No Basement, 
FHF = 25, DR = 3.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
0% 1% 2% 3% 4% 5% 6% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 
Figure 29. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 2-story, No Basement, 
FHF = 25, DR = 7.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
0% 1% 2% 3% 4% 5% 6% 7% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Figure 30. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 2-story, No Basement, 
FHF = 50, DR = 3.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
4
0% 1% 2% 3% 4% 5% 6% 7% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 
Figure 31. B/C Ratio versus Cost to Elevate with Freeboard (A Zone, 2-story, No Basement, 
FHF = 50, DR = 7.0%, UL = 30 Years, Contents @ 30%) 
0
1
2
3
0% 1% 2% 3% 4% 5% 6% 7% 
Cost to Elevate Above BFE (% of Construction Cost at BFE) 
B/C Ratio
Freeboard = 1 ft 
Freeboard = 2 ft 
Freeboard = 3 ft 
Freeboard = 4 ft 

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Table 24. Percent* of Additional Construction Cost Justified (B/C > 1.0) for Various Combinations of Freeboard, Flood 
Hazard Factor and Discount Rate (A Zone, 1-story, useful life =30 Years, Contents Value = 30% of structure value) 
Discount Rate = 3.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 4 3 2 2 1 
2 5 4 3 3 3 
3 6 5 5 4 4 
4 6 5 5 5 4 
Discount Rate = 5.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 3 2 2 1 1 
2 4 3 3 2 2 
3 4 4 4 3 3 
4 5 4 4 4 3 
Discount Rate = 7.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 2 2 1 1 1 
2 3 3 2 2 2 
3 4 3 3 3 3 
4 4 4 3 3 3 
Discount Rate = 9.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 2 1 1 1 0.5 
2 3 2 2 2 1 
3 3 3 2 2 2 
4 3 3 3 3 2 
* Percentages rounded to the nearest 1%. If the justified cost was less than 1.0% of the initial construction cost, it was rounded to 
the nearest 0.5%. Percentages account for flood damage to structure and contents only, and would be higher if displacement costs 
and flood insurance premium savings were included. 
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Table 25. Percent* of Additional Construction Cost Justified (B/C > 1.0) for Various Combinations of Freeboard, Flood 
Hazard Factor and Discount Rate (A Zone, 2-story, useful life =30 years, contents value = 30% of structure value) 
Discount Rate = 3.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 2 2 2 1 1 
2 3 3 2 2 2 
3 3 3 3 3 2 
4 3 3 3 3 3 
Discount Rate = 5.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 2 1 1 1 0.5 
2 2 2 2 2 1 
3 3 2 2 2 2 
4 3 3 3 3 2 
Discount Rate = 7.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 2 1 1 0.5 0.5 
2 2 2 1 1 1 
3 2 2 2 2 2 
4 2 2 2 2 2 
Discount Rate = 9.0% 
FHF 
Freeboard (ft) 
25 50 75 100 150 
1 1 1 0.5 0.5 0.5 
2 2 1 1 1 1 
3 2 2 2 2 1 
4 2 2 2 2 2 
* Percentages rounded to the nearest 1%. If the justified cost was less than 1.0% of the initial construction cost, it was rounded to 
the nearest 0.5%. Percentages account for flood damage to structure and contents only, and would be higher if displacement costs 
and flood insurance premium savings were included. 
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7.3.3. Sensitivity of B/C Results to Displacement Costs 
The sensitivity of the B/C results to the inclusion of displacement costs was investigated 
for V zones, Coastal A zones and A zones (both, one- and two-story buildings). Monthly 
displacement costs were expressed as a percentage of the initial building cost, and BCA model 
default displacement times were used. The results show that inclusion of displacement costs acts 
to increase the B/C for a given scenario (i.e., shifting the B/C curves in Figures 16-19 and 24-31 
upward), although the increase is not dramatic (see Table 26). 
TABLE 26. B/C Change Due to Inclusion of Displacement Costs = 1.0% of Initial Building Cost 
Flood Hazard Zone, Building Average Ratio# of B/Cs Range of B/C Ratios# 
A Zone, 1-story* 1.11 1.07 to 1.14 
A Zone, 2-story* 1.08 1.03 to 1.12 
Coastal A Zone and V Zone, 1- and 2-story^ 1.11 1.11 to 1.12 
* averaged across FHF = 25, 50, 75, 100 and 150 
^ averaged across BFE = 12, 14, 16, 18 and 20 ft 
# Ratio of B/Cs = B/C with Displacement Cost divided by B/C without displacement cost 
While the effect of including displacement costs varies slightly between flood hazard 
zones and with number of stories in an A zone, the effect can be generalized as follows: adding 
monthly displacement costs equal to 1% of the initial building cost (i.e., $2,000/month for a 
$200,000 building) increases the computed B/C by approximately 10%. If an initial B/C was 2.0, 
inclusion of a monthly displacement cost of 1% results in a B/C of approximately 2.2. 
The effect scales linearly with the relative displacement cost. For example, if the monthly 
displacement cost is equal to 0.5% of the initial building cost ($1,000/month for the $200,000 
house), the computed B/C increases by approximately 5%. If the monthly displacement cost is 
equal to 0.3% of the initial building cost ($700/month for the $200,000 house), the computed 
B/C increases by approximately 3%, etc. 
The inclusion of reasonable displacement costs in the B/C calculations should not have a 
significant effect on the additional justified costs shown in Tables 23-25 (since the values 
contained in the tables have been rounded to the nearest 1%), and those tables will be applicable 
for the generalized analyses, without or with displacement costs. If a user is interested in a 
particular building, it is suggested that the BCA model be used with inputs specific to the 
scenario, including any projected displacement costs. 
7.3.4. Effects of Flood Insurance Premium Savings Due to Freeboard 
The value of flood premium discounts for adding freeboard was also investigated. The 
StandardFlood program was used to calculate 2006-2007 flood insurance premiums for V zone 
and A zone buildings39 with the maximum coverage available through the NFIP ($250,000 
structure value, $100,000 contents value). Premiums were first calculated for each flood hazard 
39 Flood insurance premiums for Coastal A zone buildings are included in the A zone buildings  the NFIP does not 
have separate premium rates for Coastal A zone buildings. 
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zone with buildings at the BFE, and then calculated for the same buildings with 1 ft, 2 ft, 3 ft and 
4 ft of freeboard. Annual savings were calculated by subtracting the with-freeboard premium 
from the at-BFE premium, and dividing by the at-BFE premium. Results are shown in Table 27. 
TABLE 27. Annual Savings (expressed as a percentage of initial building cost, rounded to the nearest 0.1%) Due to 
Flood Insurance Premium Discounts for Freeboard (assumptions: maximum NFIP coverage, $250,000 building, 
$100,000 contents; $500 deductible; V zone, no obstructions; A zone, no basement; no CRS discount) 
Freeboard V Zone A Zone, 1-story A Zone, 2-story 
1 ft 0.5% 0.1% 0.1% 
2 ft 1.0% 0.2% 0.1% 
3 ft 1.2% 0.3% 0.1% 
4 ft 1.4% 0.3% 0.1% 
The average at-BFE A zone premium was approximately $1,000/year, while the at-BFE 
V zone premium was approximately $5,000/year. Thus, a 0.2% annual savings for a $250,000 
A zone building is equivalent to approximately $500/year, or a 50% annual flood insurance 
premium discount. A 1.3% annual savings for a $250,000 V zone building is equivalent to 
approximately $3,300/year, or a 66% annual flood insurance premium discount. 
Even if future building and contents damages prevented are not considered, the annual 
flood premium savings are generally sufficient to pay for the costs of adding freeboard in a few 
years time for many buildings. For example, consider the $250,000 V zone house mentioned 
above. Calculations in Section 7.4 showed that the per-foot cost of freeboard added at the time of 
initial construction is approximately 0.25% to 0.5% of the cost of the house constructed to the 
BFE. Table 27 shows that the flood premium savings for this house would be approximately 
0.4% to 0.5% per foot of freeboard added. The ratio of the annual flood premium savings to the 
freeboard cost varies from 0.8 to 2.0, and calculations show the time required to recover the 
freeboard cost through flood premium savings varies from approximately 6 months to 16 
months. Adding freeboard in this case will pay for itself rapidly. Even if the freeboard costs 
calculated in Section 7.4 are low, the time required to recover the freeboard cost is still short  if 
the cost to add freeboard is double that calculated in Section 7.4, the time required to recover the 
freeboard cost is approximately one to three years. 
For a $250,000 A zone house on a 8-in wall foundation with interior piers40, Section 7.4 
showed the per-foot cost of adding freeboard would be approximately to 0.8% of the at-BFE 
construction cost. Table 27 shows that the flood premium savings for this house would be 
approximately 0.1% per foot for the first foot of freeboard added (there is no meaningful flood 
insurance premium discount in zone A for more than one foot of freeboard for a 2-story house, or 
two feet of freeboard for a 1-story house). The ratio of the annual flood premium savings to the 
freeboard cost is approximately 0.1, and calculations show the time required to recover the 
freeboard cost through flood premium savings would be over 15 years. The difference between 
the V zone and the A zone results is due to the lower flood insurance premiums (and lower 
40 This cost A zone house would be 2-story, 4,800 sq ft in this study. 
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discounts) for A zone houses, and higher relative costs for adding height to the wall and interior 
pier foundation. 
This analysis was generalized to allow building owners and designers to determine the 
time required to recover the costs of including freeboard through future flood premium savings  
for buildings in any flood hazard zone. The results of the analysis are shown in Figure 40 and 
Table 28. Both the table and the figure require an estimate of the ratio of the annual flood 
premium savings to the freeboard cost. For ratios greater than approximately 0.2, the results are 
not sensitive to the discount rate chosen. 
Figure 40. Years to Recover Cost of Freeboard Through Annual Flood 
Insurance Premium Savings 
0
5 
10 
15 
20 
25 
30
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 
Annual Flood Premium Savings / Freeboard Cost 
Years 
DR = 3% 
DR = 5% 
DR = 7% 
DR = 9% 

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Table 28. Time to Recover Cost of Adding Freeboard at Time of Construction, through Annual Flood Premium Savings*. 
Ratio of Annual 
Flood Premium 
Savings to 
Freeboard Cost 
Average time 
(years) to recover 
freeboard cost (DR 
= 3% to 9%) 
Time to recover 
freeboard cost 
(years) with DR 
= 3% 
Time to recover 
freeboard cost 
(years) with DR 
= 5% 
Time to recover 
freeboard cost 
(years) with DR 
= 7% 
Time to recover 
freeboard cost 
(years) with DR 
= 9% 
0.1 17.7 12.1 14.2 17.8 26.7 
0.2 6.2 5.5 5.9 6.4 6.9 
0.3 3.8 3.6 3.7 3.9 4.1 
0.4 2.8 2.6 2.7 2.8 3.0 
0.5 2.2 2.1 2.2 2.2 2.3 
0.6 1.8 1.7 1.8 1.8 1.9 
0.7 1.5 1.5 1.5 1.6 1.6 
0.8 1.3 1.3 1.3 1.4 1.4 
0.9 1.2 1.1 1.2 1.2 1.2 
1.0 1.1 1.0 1.1 1.1 1.1 
1.5 0.7 0.7 0.7 0.7 0.7 
2.0 0.5 0.5 0.5 0.5 0.5 
* This analysis does not consider damages avoided due to freeboard; it only considers 2006-07 flood insurance premium savings. 
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8. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 
8.1. Study Intent and Overview 
NFIP minimum building standards relate principally to elevating a building to the BFE, 
use of flood-resistant materials below the BFE, and prohibiting certain types of foundations in V 
zones. The purpose of this study was to evaluate NFIP design and construction requirements, 
with particular emphasis on: 1) damages prevented or induced by strict adherence to those 
minimum requirements, and 2) the costs and benefits of modifying the minimum requirements to 
reduce building damages during flooding. 
This study was designed and conducted to address three sets of questions regarding NFIP 
building standards for typical single family homes in the SFHA: 
 What impacts have the NFIPs building standards for new construction in Special 
Flood Hazard Areas had on risk exposure and property loss? Which standards are 
the most and least effective in reducing exposure and property losses due to 
floods? Is the cost of implementing the major standards commensurate with their 
benefits? 
 Are the NFIPs standards for construction and building design adequate and 
sufficiently stringent so that losses are minimized at a reasonable cost to 
communities and property owners when flood damage occurs? Are the standards 
and incentives sufficient to protect against flood risks that may be increasing in 
the future? 
 Do the NFIPs building standards effectively protect buildings from damages 
during the 100-year flood? If current standards are not effective, how should 
FEMA change them? Are higher levels of protection achievable and more 
important, are the benefits achieved by these standards commensurate with the 
costs associated with meeting them? 
These issues were addressed through a study that included the following: 
 review of building flood damage and foundation performance in coastal and noncoastal 
floodplains. 
 review of the literature and calculation of construction costs for typical houses 
with several foundation types under a variety of flood conditions. 
 calculation of the costs of adding freeboard and changing foundations. 
 calculation of the maximum justified cost of mitigation, i.e., freeboard and/or 
foundation changes at the time of initial construction -- expressed as a percentage 
of initial construction cost -- that would yield a B/C greater than or equal to 1.0. 
All cost inputs were expressed as a percentage of the initial (at-BFE) construction 
cost to generalize the results. The B/C results depend on damages avoided, and do 
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not include other economic losses to the building owner or community (such as 
clean-up and demolition costs, uninsured losses, displacement and relocation 
costs, loss of jobs and tax base, etc.), thus, the results reported here understate the 
benefits associated with exceeding NFIP minimum building standards. 
 examination of the sensitivity of the B/C results to inclusion of displacement costs 
when building occupants must move out of flood damaged homes. 
 examination of flood insurance premium discounts for adding freeboard, and 
development of a general method to determine the time to recover the costs of 
freeboard through future flood insurance premium savings. 
8.2. Study Findings 
The general findings of this study are: 1) for the buildings analyzed, the cost of adding freeboard 
or installing a more flood-resistant foundation at the time of construction is modest but the 
benefit of doing so can be great, particularly in coastal areas subject to wave effects and riverine 
floodplains with small flood hazard factors; and 2) NFIP floodplain management regulations 
and flood insurance premium rates generally promote sound construction practices and reduce 
potential flood damages, but some changes are warranted to provide additional incentives for 
flood loss reduction and to eliminate disincentives. 
Detailed findings are listed below: 
1. Calculations show pier foundations are generally the most cost effective for A zones and 
some Coastal A zones (where scour is not expected), with the exception of slab-on-fill 
foundations in A zones where the height of the fill pad is low (less than two feet). The 
advantage of fill quickly disappears as the fill pad height increases. 
2. Pile foundations cost more than traditional masonry pier foundations, but are recommended 
in situations where scour is likely during the base flood. 
3. At the time of initial construction, the incremental costs of replacing minimally compliant A 
zone foundations (such as slab-on-fill and crawlspace foundations) with pier foundations or 
pile foundations are relatively small, generally less than 5% to 10% of the cost of the 
building. In Coastal A zones, post-storm field studies have shown that minimally compliant 
A zone foundations often fail, and this replacement is warranted. In A zones outside coastal 
areas, NFIP compliant slab-on-fill and crawlspace foundations are generally adequate, and 
the incremental cost of changing to a pile foundation is not likely justified (but owners may 
wish to do so to create under-house parking). However, changing to a pier foundation is 
probably justified, especially for flood depths more than a few feet above grade. 
4. At the time of initial construction, the cost of incorporating freeboard in a pile foundation 
averages approximately 1% to 2% of the at-BFE building cost for 4 ft of added freeboard 
(approximately 0.25% to 0.5% per foot of freeboard). 
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5. At the time of initial construction, the cost of incorporating freeboard in a masonry pier 
foundation averages approximately 1% to 2% of the at-BFE building cost for 4 ft of added 
freeboard (approximately 0.25% to 0.5% per foot of freeboard). 
6. At the time of initial construction, the cost of incorporating freeboard in a masonry wall with 
interior pier (crawlspace) foundation averages approximately 3% to 6% of the at-BFE 
building cost for 4 ft of added freeboard (approximately 0.8% to 1.5% per foot of freeboard). 
7. At the time of initial construction, the cost of incorporating freeboard in a fill foundation 
averages approximately 3% to 11% of the at-BFE building cost for 4 ft of added freeboard. 
Although the fill quantity and fill cost do not increase linearly with freeboard, they add an 
average of 0.8% to 3.0 % per foot of freeboard to the at-BFE building cost. 
8. FEMAs BCA model was modified in this study to allow generalized benefit/cost 
calculations to be made with all cost inputs expressed as a percentage of the initial (at BFE) 
building cost. The model was run with variable discount rates (ranging from 3% to 9%), 
flood damage functions (V and Coastal A, and A), BFEs (in coastal areas, ranging from 12 ft 
to 20 ft msl) and Flood Hazard Factors (in riverine areas, ranging from 25 to 150). The 
model was run only with building and contents damages, and other costs (e.g., clean-up and 
demolition costs, uninsured losses, displacement and relocation costs, loss of jobs and tax 
base, etc.) were ignored. The resulting B/C values are conservative, and will understate the 
true B/C of the actions studied. 
9. As expected, the B/C ratios decrease with increasing discount rate, with all other factors held 
constant. B/C ratios also decrease with increasing BFE and FHF, indicating that a foot of 
freeboard is worth less (in terms of damage reduction) in areas where there is a greater 
vertical spread in flood elevations associated with different return periods. 
10. V zone and Coastal A zone B/C calculations were tabulated and the B/Cs were determined 
for various combinations of freeboard, additional construction cost and discount rate. The 
data were then examined to identify the percent of additional construction cost that an owner 
would be justified in spending at the time of construction (B/C = 1.0) for each freeboard- 
BFE-discount rate combination. In the V zone and Coastal A zone cases studied, the 
calculations show41: 
 For 1 foot of freeboard above the BFE: spending 103% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 107% of the at-BFE 
building cost. 
 For 2 feet of freeboard above the BFE: spending 104% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 111% of the at-BFE 
building cost. 
41 Note that the results cited below account only for damage to the buildings and their contents. Any additional costs 
resulting from the and any cost savings as a result of adding freeboard (e.g., flood insurance premium reductions) 
will make spending even more money at the time of initial construction justified. 
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 For 3 feet of freeboard above the BFE: spending 105% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 113% of the at-BFE 
building cost. 
 For 4 feet of freeboard above the BFE: spending 106% of the at-BFE building cost is 
justified, and in some cases it may be worth spending up to 114% of the at-BFE 
building cost. 
11. A zone B/C calculations were tabulated and the B/Cs were determined for various 
combinations of freeboard, additional construction cost and discount rate. The data were then 
examined to identify the percent of additional construction cost that an owner would be 
justified in spending at the time of construction (B/C = 1.0) for each freeboard-BFE-discount 
rate combination. A zone calculations show42: 
 Over the ranges of BFEs and FHFs considered, the A zone, 1-story B/C ratios are 
approximately one-third of the V zone B/C ratios, with other factors held constant. 
The A zone, 2-story B/C ratios are approximately one-fourth of the corresponding V 
zone B/C ratios. The reductions in the B/C are attributable to different depth-damage 
functions. 
 B/C ratios for two-story buildings are less than for corresponding one-story buildings 
due to lower depth-damage functions. 
In the one-story A zone cases studied, the calculations show: 
 For 1 foot of freeboard above the BFE: spending 100.5% of the base building (at 
BFE) cost is justified, and it may be worth spending up to 104% of the base building 
cost. If the FHF = 150, DR = 9.0% results are excluded, spending 101% of the base 
building cost is justified. 
 For 2 foot of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending up to 105% of the base building cost. If the 
FHF = 150, DR = 9.0% results are excluded, spending 102% of the base building cost 
is justified. 
 For 3 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 106% of the base building cost. 
 For 4 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 106% of the base building cost. If the FHF = 
150, DR = 9.0% results are excluded, spending 103% of the base building cost is 
justified. 
In the two-story A zone cases studied, the calculations show: 
42 Note that the results cited below account only for damage to the buildings and their contents. Any additional costs 
resulting from the flooding and any cost savings as a result of adding freeboard (e.g., flood insurance premium 
reductions) will make spending even more money at the time of initial construction justified. 
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 For 1 foot of freeboard above the BFE: spending 100.5% of the base building (at 
BFE) cost is justified, and it may be worth spending 102% of the base building cost. 
 For 2 feet of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. 
 For 3 feet of freeboard above the BFE: spending 101% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. If the FHF = 
150, DR = 9.0% results are excluded, spending 102% of the base building cost is 
justified. 
 For 4 feet of freeboard above the BFE: spending 102% of the base building cost is 
justified, and it may be worth spending 103% of the base building cost. 
12. A comparison of the costs of adding freeboard and the results of the B/C analyses (i.e., items 
4 through 7 compared with item 11 above) show that freeboard in V zones is almost always 
justified; that freeboard in A zones is usually justified for pier foundations, sometimes 
justified for wall foundations, but rarely justified for slab-on-fill foundations. In the latter 
case, a switch to another foundation type would usually be justified, however. 
13. A sensitivity analysis was undertaken to investigate the effect of including displacement 
costs in the B/C calculations. Using BCA default displacement times, the effect varies 
slightly between flood hazard zones and with number of stories in an A zone. However, the 
effect can be generalized as follows: adding monthly displacement costs equal to 1% of the 
initial building cost increases the computed B/C by approximately 10%, and so forth. 
14. The relationship between initial freeboard costs and flood premium discounts was also 
considered in a separate analysis. Even if future building and contents damages prevented are 
not considered43, the annual flood premium savings are generally sufficient to pay for the 
costs of adding freeboard in several years time for many buildings. In the case of V zone 
buildings, the time required to recover freeboard costs through flood premium savings is 
short  a year or two. In the case of A zone buildings, the recovery time can extend to more 
than 15 years, due to the lower A zone premiums and premium discounts, which are used to 
offset the initial freeboard cost. 
8.3. NFIP Building Standards: Effectiveness and Costs 
On an individual building level, NFIP building standards have reduced flood damage 
relative to nearby pre-FIRM type structures. Flood losses for new construction are reduced 
through elevation and proper selection of the building foundation. Post-storm observations and 
calculations made during this study demonstrate that incorporation of freeboard is one of the 
most effective means of reducing property losses. In coastal areas subject to waves and erosion, 
post-storm observations have demonstrated the importance of FEMAs free-of-obstruction rule 
and use of pile or pier foundations with sufficient embedment to resist scour and lateral loads. 
43 If the damage reduction and flood premium savings are considered jointly, higher B/Cs and reduced freeboard 
cost recovery times result. 
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Calculations performed during this study and obtained from the literature show that the 
additional costs of adding freeboard at the time of construction are small, and would generally 
return benefits in excess of the costs, particularly in V zones and Coastal A zones, and in noncoastal 
A zones with low Flood Hazard Factors44. The additional costs of modifying foundation 
types would also return benefits in excess of costs, particularly in coastal flood hazard areas. 
While this study did not investigate building practice effects on flood loss reduction at a 
community level, extension of the individual building findings to a broader scale seems 
reasonable. Reduced flood damage to individual buildings aggregates to reduced flood losses and 
disruption to the community. Study authors have observed this first-hand as part of post flood 
investigations -- where flood damage was widespread and great, individuals and communities 
often struggle to recover, while other nearby communities with less flood damage recover 
quickly. 
This study did not investigate the effects of potential changes in NFIP building standards 
on the flood insurance fund, disaster assistance payments and other financial aspects of the NFIP 
and FEMA. However, since modified building standards could reduce flood damage at the 
individual building level, it seems reasonable to expect flood claims, disaster assistance and 
other post-disaster payments might also be reduced. The exact impact on the NFIP would depend 
on flood premiums received and payments made. The study authors believe that the cost of 
implementing building standards changes would be small, since the NFIP and the participating 
communities already enforce standards which are similar to the changed standards this study 
recommends. 
Moreover, under the current flood premium rate structure, flood premium discounts will 
be sufficient to recover the incremental costs borne by property owners due to building standard 
changes -- in just a few years time for many buildings. These results suggest that, for the types of 
buildings analyzed here, flood losses can be reduced now and in the future through small 
expenditures at the time of new construction. 
8.4. Do NFIP Building Standards Minimize Losses, Now and in the Future? 
Generally speaking, NFIP building standards do reduce flood losses to new construction 
under present day base flood events. However, building standards are implemented in 
conjunction with the FIRM, which does not account for increasing flood hazards in the future. 
Thus, while NFIP building standards may be generally effective today, their future effectiveness 
will be reduced as the FIRM becomes obsolete due to changing flood conditions. Revising 
building standards may be one way to compensate for changing flood conditions in the future. 
This study showed that building damages under base flood conditions could be reduced, at 
modest cost, by incorporating freeboard and/or changing the foundation type. These actions 
would also help to reduce future flood damage resulting from sea level rise and erosion in coastal 
areas, and from development impacts in riverine areas. . 
44 A floodplain area with a low Flood Hazard Factor is characterized by a 100-year flood level that is no more than a 
few feet above the 10-year flood level. 
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8.5. NFIP Building Standards and Protection During the 100-Year Flood 
With three exceptions, noted below, NFIP building standards evaluated by this study 
generally protect against the 100-year flood. However, floods more severe than the 100-year 
flood do occur, and incorporation of freeboard and modified foundations can help reduce losses 
from such floods. The B/C analyses indicate that there is a damage reduction benefit by taking 
such actions, and additional analyses might help to define a flood return period to which 
additional elevation is justified. This study indicates that higher levels of protection are 
achievable, and that the benefits of doing so will exceed the costs, particularly in high hazard 
areas. 
Constructing a minimally compliant A zone building with the top of the lowest floor at 
the BFE is not an effective way to reduce flood damage  it actually guarantees flood damage 
will occur to the typical residential building during the base flood (i.e., flood damage to the floor 
system, floor and floor covering [through direct contact with floodwaters] and flood damage to 
walls [through wicking action]. Although NFIP regulations require the use of flood damage 
resistant materials below the BFE, many floor systems, floors and floor coverings are prone to 
flood damage. Given the modest costs of adding freeboard at the time of construction, it seems 
prudent to change the lowest floor reference elevation in A zones to be consistent with that in V 
zones the bottom of the lowest horizontal supporting structural member supporting the lowest 
floor. 
Another ineffective NFIP building standard allows buildings in Coastal A zones to be 
supported on fill and/or shallow foundations. Many of these foundations cannot withstand scour 
and lateral flood loads that will be experienced just landward of the V/A boundary during the 
base flood. Flood loads and conditions in Coastal A zones, which can include damaging waves 
and erosion, are different that those in riverine or lacustrine A zones which are usually subject to 
inundation and slowly moving water. By using the same minimum building standards for all A 
zones, regardless of the source and severity of the flood forces, it appears the NFIP 
unintentionally reduces the degree of flood resistance built into minimally compliant A zone 
structures in coastal areas. 
Finally, studies of flood damage in coastal areas by Rogers (2005) have found that the 
NFIP penalizes some non-V zone pile-supported buildings through increased flood premiums 
and/or reduced flood policy coverage. Owners and builders, apparently sensitive to these 
disincentives, have adopted NFIP-compliant but inferior construction practices which render 
buildings more vulnerable to flood damage in the event that flood levels rise above the lowest 
floor. This piling penalty is contrary to flood damage reduction promoted by the NFIP. 
8.6. Recommendations 
B-1. The NFIP should not allow new A zone construction to be built with the top of the 
lowest floor at the BFE. Instead, the NFIP should require the top of the lowest floor 
of A zone structures to be built above the BFE such that the floor system is not in 
contact with flood waters during the base flood. This could be accomplished by 
either: 1) requiring sufficient freeboard, or 2) by changing the lowest floor reference 
elevation in A zones to be consistent with V zones (i.e., the bottom of the lowest 
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horizontal structural member supporting the lowest floor must be at or above the 
BFE). 
B-2. The NFIP should require at least 1 foot of freeboard for all new construction in the 
special flood hazard area. The exact freeboard amount should be guided by several 
factors: 
 Freeboard requirements contained in consensus standards such as ASCE 24 (ASCE 
2005). ASCE 2445 contains freeboard provisions which vary by building importance 
(the standard requires critical facilities to be elevated higher above the BFE than 
typical residential structures, for example). The ASCE 24 freeboard provisions 
apply to the lowest floor, the use of flood resistant materials and utilities. 
 Future flood conditions. ASCE 24 does not account explicitly for future increases in 
flood hazards, thus, freeboard in excess of ASCE 24 requirements may be 
appropriate in some flood hazard areas. The NFIP should consider flood loss 
reduction under present day base flood conditions and under future flood conditions 
when it establishes freeboard requirements. 
 Flood elevation frequency. The NFIP should attempt to establish freeboard 
requirements that are consistent with the flood risk. For example, 1 foot of 
freeboard at a site with a flood hazard factor of 20 may yield protection against a 
certain flood return period event. Equivalent protection at a site with a flood hazard 
factor of 75 would require more than 1 foot of freeboard. 
B-3. The NFIP should mandate V zone design and construction practices in Coastal A 
zones (e.g., requiring open foundations and the area below the BFE to be free of 
obstructions, making the lowest floor reference elevation the bottom of the lowest 
horizontal structural member supporting the lowest floor, designing for simultaneous 
action of flood and wind). Some communities have mandated V zone standards in A 
zones for years, but implementation of this recommendation on a larger scale would 
require changes to the flood hazard mapping process and the FIRM46. Note that the 
2005 edition of ASCE 24 requires new construction in Coastal A zones to meet V 
zone standards, and the FEMA has published supporting post-Katrina guidance. 
B-4. The B/C results of this study are sensitive to the flood depth-damage function used in 
the analysis. The NFIP should, on an ongoing basis, review and update depth-damage 
functions based on flood claims data, results of MAT investigations and other data. 
This may require collection of some data now deemed optional during the flood 
claims adjustment process. 
45 At present, ASCE 24 is adopted by reference by the International Building Code (International Code Council 
[ICC] 2006a) and by the National Fire Protection Associations (NFPA) Building Construction and Safety Code 
(NFPA 2006), but not by the International Residential Code (ICC 2006b) 
46 Post-Katrina flood hazard maps in Mississippi will show the landward limit of the 1.5 ft breaking wave height, 
which can serve as the landward boundary of the Coastal A Zone. This is the first time that such a designation will 
be shown on a FIRM. 
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B-5. Flood insurance premium rates should reflect anticipated flood damages and provide 
incentives to property owners and communities to exceed minimum NFIP building 
standards. The Community Rating System (CRS) does this on a community scale, but 
additional effort is needed to provide incentives to individuals. For example: 
 The NFIP should re-evaluate flood insurance premium discounts for buildings in 
A zones. Current A zone discounts effectively cease at one to two feet above the 
BFE (unlike V zones where substantial discounts are awarded for up to four feet 
of freeboard). Additional discounts for increased freeboard in A zones may be one 
of the most powerful arguments that can be made to property owners. 
 The NFIP should revise flood premium rates and coverage for NFIP-compliant 
pile-elevated buildings outside the V zone. Present rates and coverage penalize 
property owners who might otherwise adopt the superior pole-type construction, 
with pilings extending above the lowest floor to a higher floor or the roof. 
B-6. The NFIP should consider development of an A Zone Risk Factor Rating Form and 
process, similar to that in place for V zones. This action could provide another way to 
reward A zone building owners to adopt design and construction practices that exceed 
NFIP minimum standards. 

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9. ACRONYMS 
AIR American Institutes for Research 
ASCE American Society of Civil Engineers 
ASFPM Association of State Floodplain Managers 
B/C benefit-cost ratio 
BCA benefit-cost analysis 
BFE base flood elevation 
BPAT (FEMA) Building Performance Assessment Team 
CHHA coastal high hazard area 
CFR Code of Federal Regulations 
CRS Community Rating System 
DR discount rate 
FEMA Federal Emergency Management Agency 
FHF flood hazard factor 
FIA Federal Insurance Administration 
FIRM Flood Insurance Rate Map 
ft foot or feet 
ICC International Code Council 
in inch or inches 
lf linear foot 
MAT (FEMA) Mitigation Assessment Team 
msl mean sea level 
NAVFAC Naval Facilities Engineering Command 
NFIP National Flood Insurance Program 
NFPA National Fire Protection Association 
NFPC (USACE) National Flood Proofing Committee 
OMB United States Office of Management and Budget 
PFD primary frontal dune 
psf pounds per square foot 
sf square foot or square feet 
SFHA Special Flood Hazard Area 
SWL stillwater level or stillwater elevation 
UL useful life 
USACE United States Army, Corps of Engineers 
USGS United States Geological Survey 
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10. REFERENCES 
ASCE. 2002. Minimum Design Loads for Buildings and Other Structures. ASCE Standard 
ASCE/SEI 7-02. 
ASCE. 2005. Flood Resistant Design and Construction. ASCE Standard ASCE/SEI 24-05. 
ASFPM. 2000. Mitigation Success Stories, 3rd edition. Available at 
http://www.floods.org/publications/mit%20succ%20stories/mssiii1.htm#home 
ASFPM. 2002. Mitigation Success Stories, 4th edition. Available at 
http://www.floods.org/publications/mit%20succ%20stories/mssiv1.htm 
EQE. 2000. HAZUS Preview Model Methods and Data. Final Technical Report to the 
National Institute of Building Sciences. 
FEMA. 1980. Elevating to the Wave Crest Level: A Benefit-Cost Analysis. FIA-6. 
FEMA. 1986. Coastal Construction Manual. FEMA-55, second edition. 
FEMA. 1993. Technical Information on Elevating Substantially Damaged Residential Buildings 
in Dade County. 
FEMA. 1998. Homeowners Guide to Retrofitting. FEMA-312. Available at 
http://www.fema.gov/rebuild/mat/fema312.shtm 
FEMA. 2000. Coastal Construction Manual: Principles and Practices of Planning, Siting, 
Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas. 
FEMA-55, third edition. 
FEMA. 2003. Guidelines and Specifications for Flood Hazard Mapping Partners, Appendix D: 
Guidance for Coastal Flooding Analyses and Mapping. Available at 
http://www.fema.gov/plan/prevent/fhm/gs_main.shtm 
FEMA. 2004, Guidelines for Benefit-Cost Analysis, Attachment IV. Available at 
http://www.fema.gov/pdf/fima/guidelines_for_bca.pdf. 
FEMA. 2005a. Design and Construction in Coastal A Zones. Hurricane Katrina Recovery 
Advisory. Available at http://www.fema.gov/pdf/rebuild/mat/coastal_a_zones.pdf 
FEMA. 2005b. Home Builders Guide to Coastal Construction. FEMA 499, Technical Fact 
Sheet Series. Available at http://www.fema.gov/rebuild/mat/mat_fema499.shtm 
FEMA. 2005c. V Zone Risk Factor Rating Form. Available as part of the Flood Insurance 
Manual at http://www.fema.gov/business/nfip/manual.shtm 
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FEMA. 2005d. A Comparative Cost Evaluation of Foundation Types Permitted by NFIP 
Regulations in Coastal A Zones and V Zones. Memorandum from D. Powell to S. Saifee, 
December 4, 2005. 
FEMA. 2005e. Mitigation BCA Toolkit, Version 2.0, January 2005. CD-ROM. 
FEMA. 2005f. Benefit-Cost Analysis of Hazard Mitigation Projects, Volume 2, Coastal A Zone 
Flood. Users Guide Version 1.0, Revised. January 2005. 
FEMA. 2006a. Recommended Residential Construction for the Gulf Coast, Building on Strong 
and Safe Foundations. FEMA 550. 
FEMA. 2006b. Hurricane Katrina Mitigation Assessment Team Report. FEMA 549. In Press, 
will be available at http://www.fema.gov/rebuild/mat/mat_reprts.shtm. 
FEMA. 2006c. Designing for Flood Levels Above the BFE. Hurricane Katrina Recovery 
Advisory. In Press, will be available at 
http://www.fema.gov/rebuild/mat/mat_katrina.shtm 
International Code Council. 2006a, International Building Code. 
International Code Council. 2006b. International Residential Code. 
Jones, C, Coulbourne, W.L., and Tertell, P. 2001. Consideration of a New Flood Hazard Zone: 
the Coastal A Zone. In ASFPM, Proceedings of the 25th Annual Conference of the 
Association of State Floodplain Managers. 
Marshall & Swift. 2003. Residential Cost Handbook. 
NAVFAC. 1982. Foundations and Earth Structures. Design Manual DM7.2. 
National Fire Protection Association. 2006. NFPA 5000 Building Construction and Safety Code. 
OMB. 2006. Guidelines and Discount Rates for Benefit Cost Analysis of Federal Programs. 
OMB Circular A-94, Appendix C, Revised January 2006. Available at 
http://www.whitehouse.gov/omb/circulars/a094/a094.html and 
http://www.whitehouse.gov/omb/circulars/a094/a94_appx-c.html 
Rogers, S. M., Jr. 2005. Coastal Building Performance in Hurricane Isabel: Backward Trends in 
Design. In ASCE, proceedings of the Solutions to Coastal Disasters 2005 conference. 
Thomas, W. 2003. An Approximate Method for Estimating Flood Depths for Various 
Recurrence Intervals. Memorandum prepared for Christopher Jones, Revised Dec. 15, 
2003. 
USACE. 1975. Guidelines for Identifying Coastal High Hazard Zones. Galveston District. 
USACE. 1993. A Floodproofing Success Story along Dry Creek at Goodlettesville, Tennessee. 
Available at http://www.usace.army.mil/civilworks/cecwp/NFPC/nfpc.htm 
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USACE. 1998. Flood Proofing Performance: Successes and Failures. Available at 
http://www.usace.army.mil/civilworks/cecwp/NFPC/nfpc.htm 
USACE. 2001. Non-Structural Flood Damage Reduction within the Corps of Engineers, What 
Districts are Doing. Available at 
http://www.usace.army.mil/civilworks/cecwp/NFPC/nfpc.htm 
USGS. 1982. Guidelines for determining flood flow frequency. Bulletin 17B of the Hydrology 
Subcommittee, Interagency Advisory Committee on Water Data. 
U.S. Government Printing Office. 2005. Title 44, Code of Federal Regulations, Emergency 
Management and Assistance. Available at 
http://www.access.gpo.gov/nara/cfr/waisidx_05/44cfrv1_05.html 

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Appendix 1: NFIP Building Standards Survey 
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A seven-question survey was developed near the inception of this study to solicit 
opinions of floodplain professionals on the NFIPs minimum building standards. The survey 
was posted on Christopher Jones web site between May 20, 2003 and July 11, 2003, and its 
availability was announced to the floodplain management community. Individuals were free to 
respond voluntarily, or not to respond. In addition, Jones contacted nine individuals and solicited 
their opinions directly. A total of 58 people participated, either by email, telephone or face-toface 
interview.47 The survey questions are listed below: 
1. Are NFIP minimum standards for building design and construction rigorous enough to 
minimize losses at a reasonable cost to communities and property owners when flood 
damage occurs? 
2. Are the NFIP minimum standards sufficient to protect existing development against flood 
risks that may increase in the future (e.g., as a result of new construction causing 
increased runoff and higher BFEs, or as a result of other factors such as subsidence, sea 
level rise, coastal erosion)? 
3. Are the NFIP minimum elevation requirements (i.e., top of lowest floor in A zones, 
bottom of lowest horizontal member in V zones) justified and adequate? Should 
freeboard be mandated for certain flood hazard zones or certain types of structures? If so, 
how much freeboard is appropriate? 
4. The NFIP requires pile or column foundations and allows breakaway walls in V zones, 
and allows any type of foundation in A zones (e.g., fill, slab, foundation wall, pier, pile, 
column). Should the NFIP foundation requirements be changed for certain flood hazard 
zones or certain types of structures? 
5. What about structures built on fill in or near the SFHA  should elevation or foundation 
requirements be modified for structures in the SFHA, or mandated for structures near or 
removed from the SFHA? 
6. In your community or state, what building practices have been found effective against the 
forces and conditions associated with local flood hazards? What building practices have 
been found ineffective? Please include a description of the local flood hazards. 
7. If you were free to change anything about the NFIPs minimum design and construction 
requirements, what changes would you make? 
47 Note that this survey used non-random sampling, thus, the results may be biased toward those with strong 
opinions in favor of changing the NFIP requirements rather than maintaining the status quo. On the other hand, most 
of the responses were obtained from professionals who are involved in some aspect of floodplain management and 
coastal construction, hence, the respondents are likely to be well-informed on the subject. While the results of this 
survey are not statistically valid due to sample size and sampling methodology, the responses can still inform 
discussions of NFIP building standards. 
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The 58 survey respondents can be broken down as follows: 
 23 NFIP State Coordinators or floodplain management staff (representing 19 
states) 
 nine local floodplain managers and/or building officials (representing eight 
communities) 
 eight insurance agents or insurance industry employees 
 seven floodplain management consultants 
 seven federal employees 
 two building contractors 
 two unknown respondents 
Approximately one-half of the survey respondents represented areas with or dealt with 
riverine flooding only, while about one-half of the respondents represented areas with or dealt 
with coastal flooding (and to some extent, riverine flooding). 
Survey responses were aggregated to avoid potential identification of respondents. 
Further, since responses to some questions were quite lengthy, they were paraphrased and 
grouped with other responses to the same question. Aggregate survey responses and the most 
common responses for each question are listed below (the question is repeated, followed by a 
summary of the responses in italics). 
Note that there are always fewer than 58 responses to each question, and this is 
attributable to several factors: 1) some surveys were completed by groups rather than individuals, 
2) some respondents did not respond to every question, and 3) some responses focused on other 
aspects of the NFIP (e.g., insurance issues, hazard mapping, consistency between insurance and 
regulatory aspects of the program, etc.), and 4) the meaning of some responses was not clear. 
Thus, not all responses were counted in the tally below. Approximately 40 usable responses were 
received for most questions. 
1. Are NFIP minimum standards for building design and construction rigorous enough to 
minimize losses at a reasonable cost to communities and property owners when flood 
damage occurs? 
Yes: 17 No: 23 
2. Are the NFIP minimum standards sufficient to protect existing development against flood 
risks that may increase in the future (e.g., as a result of new construction causing 
increased runoff and higher BFEs, or as a result of other factors such as subsidence, sea 
level rise, coastal erosion)? 
Yes: 5 No: 36 
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Of those replying no, riverine respondents tended to say that future conditions hydrology 
should be considered in mapping, coastal respondents tended to say that erosion and sea 
level rise should be considered. 
3. Are the NFIP minimum elevation requirements (i.e., top of lowest floor in A zones, 
bottom of lowest horizontal member in V zones) justified and adequate? Should 
freeboard be mandated for certain flood hazard zones or certain types of structures? If so, 
how much freeboard is appropriate? 
Yes: 6 No: 34 
Responses varied, but those who responded no tended to say that a minimum of 1 ft of 
freeboard should be required, that freeboard should be sufficient to elevate the entire 
floor system above the BFE in A zones, or that freeboard should be variable (and be 
based on Benefit-Cost analysis), etc. 
4. The NFIP requires pile or column foundations and allows breakaway walls in V zones, 
and allows any type of foundation in A zones (e.g., fill, slab, foundation wall, pier, pile, 
column). Should the NFIP foundation requirements be changed for certain flood hazard 
zones or certain types of structures? 
Yes: 25 No: 11 
Of those responding yes, several thought breakaway walls should be eliminated (due to 
use of enclosed space, not due to building standards issues), several said the use of fill to 
remove a structure from the SFHA should be eliminated (even though the question did 
not address the effect of fill on mapping), and several called for V zone foundations in (at 
least part of) A zones in coastal areas. 
5. What about structures built on fill in or near the SFHA  should elevation or foundation 
requirements be modified for structures in the SFHA, or mandated for structures near or 
removed from the SFHA? 
Yes: 22 No: 7 
Of those responding yes, approximately  said one or more of the following: do not 
allow fill to be used to elevate buildings, do not allow basements to be constructed in 
areas where fill has been placed, do not allow parcels to be removed from the SFHA by 
fill placement. Approximately  of those responding yes said that fill placement was 
acceptable, but the better guidance is needed on fill compaction and protection (against 
velocity and erosion). 
6. In your community or state, what building practices have been found effective against the 
forces and conditions associated with local flood hazards? What building practices have 
been found ineffective? Please include a description of the local flood hazards. 
The most effective practices listed can be grouped into three categories, in decreasing 
order of their mention: 1) elevation and freeboard, 2) adoption and enforcement of 
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building codes and 3) avoidance of flood hazards and preservation of open space. 
Ineffective practices listed by respondents included elevation on fill and manufactured 
home installations. 
7. If you were free to change anything about the NFIPs minimum design and construction 
requirements, what changes would you make? 
Responses were varied, but can be grouped under the following categories (in no 
particular order): 1) require freeboard, including for manufactured housing, 2) 
eliminate/restrict/modify the use of fill in the SFHA, 3) restrict the use of breakaway 
walls, 4) modify substantial damage regulations to incorporate repetitive losses, 5) 
restrict siting in floodways and V zones, 6) modify the mapping of flood hazards (e.g., 
eliminate unnumbered A zones, map future conditions, map Coastal A zones, map VO 
zones and velocity in other zones, include mapping of small watersheds, improve 
mapping of debris flow, ice jams and sedimentation), 7) establish minimum floor 
elevations in recognition of the allowable rise in floodways, 8) revise flood insurance 
(e.g., increase flood insurance and Increased Cost of Compliance limits, make insurance 
and regulations consistent), 9) clarify NFIP regulations and definitions, and 10) move 
toward a no adverse impact model for hazard delineation and building regulation. 

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Appendix 2: A Comparative Cost Evaluation of Foundation Types 
Permitted by NFIP Regulations in Coastal A and V Zones 
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FEMA-1604-DR-MS 
515 East Amite Street 
Jackson, MS 39201-2709 
MEMORANDUM 
TO: Shabbar Saifee, HPA Group Supervisor 
FROM: Dan Powell, Acting HPA Group Deputy Supervisor 
Cc: Jim McCulloch, HM Architect 
DATE: December 4, 2005 
RE: A comparative cost evaluation of foundation types permitted by NFIP 
regulations in coastal A and V zones. 
Background: NFIP requirements for coastal A and V Zone foundations 
The NFIP minimum requirements for foundation design in A zones make no distinction 
between inland and coastal areas. Technical Fact Sheet No. 11, Home Builders Guide 
to Coastal Construction, acknowledges that foundation construction permitted under 
NFIP for inland A zones is generally not suitable for coastal construction. Buildings 
located in both inland and coastal A zones must be elevated so that the top of the 
lowest floor is at or above the BFE. Coastal A zones are based on a wave crest 
(equaling the BFE) between one and a half and three feet. The problem is that some 
foundation types, while suitable for inland construction and technically permitted in 
coastal A zones under NFIP regulations, are not capable of withstanding the combined 
forces of high winds, velocity flooding, scour, erosion and floating debris. Post event 
damage assessments have concluded that structures in coastal A zones are subject to 
the same combination of forces more typically associated with the high hazard coastal V 
zones. 
Coastal A zone foundation construction that has been prone to failure include slabs-ongrade 
elevated over structural fill, various types of enclosed perimeter foundations, and 
masonry pier foundations. In contrast, open foundations free of obstruction and 
consisting of piles or columns with adequate embedment to resist scour, have proven to 
be less prone to failure. In recognition of the problem, NFIP has recommended that 
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foundation design in coastal A zones comply with the more stringent requirements 
applied to V zones. 
SFHAs designated as V zones have a crest equal to or greater than three feet. 
Buildings located in V zones must be elevated on pilings or columns so that the bottom 
of the lowest horizontal structural member of the lowest floor is at or above the BFE. 
Enclosures below the BFE are prohibited. The building design must be certified by a 
licensed engineer or architect that it will resist flotation, collapse, and lateral movement 
resulting from combined wind and hydrostatic loads. The recommendation that more 
stringent V zone requirements be applied to coastal zone A buildings has raised the 
question of how much the design and construction upgrades will cost the end user. 
Costs: Coastal versus inland construction costs 
The issue of coastal versus inland home costs has already been partly addressed in 
Technical Fact Sheet No.6. The fact sheet notes that coastal homes will always cost 
more to design, construct, maintain, and insure than inland homes. They are subject to 
higher risks and the possibility of more frequent and severe damage, as well as more 
rigorous code and regulatory requirements. The argument is made that the high initial 
cost must be balanced with long-term life cycle costs. Rather than building to the 
minimum standard, a marginally larger initial investment in design and material 
upgrades could save a significant amount of money in reduced maintenance, repair, 
and insurance premiums over the long haul. The discussion concludes with a table 
breaking down the added initial costs for different design items that are required by 
codes or NFIP for coastal home construction in A and V zones. Based on the analysis, 
coastal homes cost 15% - 30% more than homes in inland areas. Also included is a list 
of costs for design items that exceed minimum code/NFIP requirements but further 
reduce various life cycle cost. These additional items added 5% to the base building 
cost. The total construction cost for required design features and optional upgrades 
above code is in the 20% - 35% range for coastal construction in A and V zones. 
Because both A and V zones are lumped together in the analysis, what is not so clear is 
the expected cost for applying the more stringent and expensive V zone requirements to 
coastal A zones. In the preceding analysis referred to, the additional cost of pile/column 
foundations for both A and V zones is noted only as greater than 2% of the base 
building cost. How much greater? Code mandated wind zone requirements would be 
similar for both A and V zones, therefore the cost should remain relatively constant for a 
given structure regardless of the zone in which its located. As far as building codes are 
concerned, what will govern a structure supported on an open foundation design and 
located in a high wind zone will be the tendency of the building to overturn. Building 
codes currently have no provisions for structural design guidelines addressing the 
impact of storm surge on buildings located in coastal regions. Open foundation designs 
consisting of unobstructed piles or columns offer less resistance to hydrostatic and 
hydrodynamic loads due to storm surge and will transfer to grade the dead load and 
applied live loads, including wind loads that are imposed on the superstructure. The 
importance of foundation design to the survivability of a structure subject to extreme 
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loading conditions cannot be overstated. Failure of an inadequately designed foundation 
will result in failure of the entire structure. Viewed in this light, proposed upgrades to the 
foundation design become critical and deserve a more thorough consideration of the 
cost implications. 
Cost comparison methodology: A Zone and V Zone foundation types 
(See Table 1 attached) 
Costs were developed from the 2005 Marshall & Swift cost estimating guide. To insure 
continuity with the cost analysis presented in Technical Fact Sheet No. 6, costs are 
based on the same prototype: a 3,000 square foot home of average construction 
quality, compliant with all codes, with an average perimeter/floor area ratio, and 
featuring a moderate number of windows. 
All costs are based on calculated base building costs and exclude site acquisition and 
site improvements. Calculated costs are relative and are presented as percentages to 
account for variations in square footage. Foundation type, design, depth of footing and 
corresponding cost will vary depending on site location, site context, soil bearing 
capacity, susceptibility to erosion, etc. In the examples given, pile footings have been 
embedded 10 below grade because deep embedment to protect against erosion and 
sour effects is recommended in coastal areas. The cost comparison table developed 
provides a percentage cost factor for reductions or extensions of pile footings. A cost 
estimate for reinforced concrete frame and steel moment frame have not been included 
in Table 1 as the estimating software was unavailable at the time of this analysis. 
Conclusions based on the following table of cost comparisons 
 The additional cost for upgrading an A zone foundation to comply with V zone 
requirements will vary from 1.9 % - 10.4%++ of base building cost. The higher 
the foundation elevation needed to meet the required BFE, the higher the 
percentage of foundation cost to base building cost. 
 The net additional cost to upgrade an A zone foundation to V zone requirements 
is arrived at by deducting the A zone foundation Types 1, 2, 3, or 4 from Type 5/ 
Piles/Columns. 
 Each additional foot of vertical elevation varies from 0.3% - 0.5% of base building 
cost. Adding additional freeboard will have a negligible impact on total project 
cost while providing a significant reduction in hazard. 

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Table I 
Approximate Costs - Coastal A Zone Foundation Types 
Types 1, 2, 3, & 4 are permitted by NFIP in all A zones but are not recommended 
for coastal A zones. Type 5, open foundation, is both permitted and 
recommended for coastal A zones and required in coastal V zones. 
% of Base 
Building 
Cost 
Add'l cost for 
upgrade from 
A zone, 
foundation 
Types 1 thru 
4, to V zone 
foundation 
requirements 
Type I: Concrete 8" perimeter concrete foundation w/ interior concrete piers, bottom 
of footing 3' below grade, top of foundation 2' above grade 
6.5% Not permitted 
in V zones 
Each additional vertical foot of foundation wall 1.0% 
Type 2: CMU 8" perimeter CMU foundation w/ interior CMU piers, bottom of 
footing 3' below grade, top of foundation 2' above grade 
5.5% Not permitted 
in V zones 
Each additional vertical foot of foundation wall Add 0.7% 
Type 3: Slab Concrete slab-on-grade over 1' compacted structural fill, bottom of 
perimeter footing 8" below slab 
4.4% Not permitted 
in V zones 
Each additional vertical foot of fill Add 1.2% 
Type 4: Piers, 
CMU 
Open foundation, 1'-4" square CMU piers 10' on center, bottom of 
footing 3' below grade, top of pier 2' above grade 
3.6% Not permitted 
in V zones 
Each additional vertical foot of foundation piers Add 0.2% 
Approximate Costs - Coastal V Zone Foundation Types 
Type 5: Piles, 
wood 
Open foundation, 10" diameter treated wood piles set 10' below 
grade, top of pile 3' above grade, piles at 10' on center 
8.4% 1.9% to 
4.8%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.3% 
Type 5: Piles, 
wood 
Open foundation, 12" diameter treated wood piles set 10' below 
grade, top of pile 3' above grade, piles at 10' on center 
11.3% 4.8% to 7.7%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.3% 
Type 5: Piles, 
steel 
Open foundation, 8 x 8 steel "H" piles set 10' below grade, top of 
pile 3' above grade, piles at 10' on center 
11.3% 4.7% to 7.6%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.4% 
Type 5: Piles, 
steel 
Open foundation, 10 x 10 steel "H" piles set 10' below grade, top 
of pile 2' above grade, piles at 10' on center 
14.0% 7.5% to 
10.4%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.5% 
Type 5: Piles, 
precast concrete 
Open foundation, 10" diameter precast concrete piles set 10' 
below grade, top of pile 3' above grade, piles at 10' on center 
12.1% 5.6% to 8.5%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.4% 
Type 5: Piles, 
precast concrete 
Open foundation, 12" diameter precast concrete piles set 10' 
below grade, top of pile 3' above grade, piles at 10' on center 
13.5% 7.0% to 9.9%+ 
Each vertical foot, either addition to elevation or reduction in 
embedment 
+/- 0.5% 
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Appendix 3: An Approximate Method for Estimating Flood Depths for 
Various Recurrence Intervals 
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An Approximate Method for Estimating Flood Depths 
for Various Recurrence Intervals 
December 15, 2003 
Wilbert Thomas 
An approximate method for estimating flood depths for various recurrence intervals was 
developed that utilizes the known flood depth for the 100-year flood. The flood depth for the 
100-year flood is often available from Flood Insurance Studies published by the Federal 
Emergency Management Agency. The following method is based on the slope of dischargefrequency 
curve and the relation between depth and discharge. 
Considerable research and literature are available for discharge frequency analyses based on the 
annual maximum peak discharge. Bulletin 17B, Guidelines For Determining Flood Flow 
Frequency (Interagency Advisory Committee on Water Data), documents procedures for 
estimating flood discharges for various recurrence intervals (such as the 100-year or 1-percent 
annual chance flood). The Bulletin 17B procedure is to fit a Pearson Type III frequency 
distribution to the logarithms of the annual maximum peak discharges at a given gaging station. 
The slope of the discharge-frequency curve is based on the standard deviation and coefficient of 
skewness of the logarithms of the annual maximum peak discharges. 
The equation for the discharge-frequency curve based a Pearson Type III distribution is 
log QT = log Qbar + KT * SlogQ (1) 
where log QT is the logarithm of the T-year flood discharge, log Qbar is the mean of the 
logarithms of the annual peak discharges, SlogQ is the standard deviation of the logarithms of the 
annual peak discharges, and KT is a Pearson Type III frequency factor that is a function of 
recurrence interval (T) and skewness and is given in Appendix 3 of Bulletin 17B. The relation 
between the depth of the T-year flood and the T-year discharge can be estimated based on the 
work of several investigators and basic hydraulic theory. 
For several streams in the mid-western USA, Leopold and Maddock (1953) showed that for less 
than bankfull discharge there was a relation between channel depth (d) and discharge (Q) of the 
form d = c Qf, where c and f are constants indicative of a given channel shape. Thomas (1964) 
found this type of relation applicable for greater than bankfull discharges in New Jersey, and for 
simplicity modified the equation to dT = c (Q2.33)f, where dT is the flood depth above the 50- 
percent duration flow for a given return period T, Q2.33 is the mean annual flood discharge 
(return period of 2.33 years), and c and f are constants for a given return period. 
Leopold and Maddock (1953) found that the exponent f in their equation d = c Qf averaged about 
0.40 for streams in the mid-western USA when discharges were less than bankfull. Dunne and 
Leopold (1978) found the exponent f averaged 0.38 for discharges less than bankfull for the 
upper Green River watershed in Wyoming. Leopold and others (1964) found that the exponent f 
averaged 0.52 for discharges less than bankfull for several locations in the Seneca Creek 
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watershed in Maryland. Burkham (1978) used stage-discharge relations for 539 gaging stations 
in seven states from Table 1 to define an average value of 0.42 for the exponent f for discharges 
greater than bankfull. 
Mannings open-channel flow equation can be used to illustrate that the average depth in a 
rectangular channel is proportional to the 3/5 (0.60) power of discharge and to the 3/8 (0.375) 
power of discharge in triangular channels. All these studies indicate that flood depth is 
proportional to discharge raised to a power between about 0.4 and 0.6. Since there is uncertainty 
in any relation between depth and discharge, an exponent of 0.6 is recommended for the relation 
between T-year flood depth (dT)and discharge (QT) as follows: 
dT = c (QT)0.6. (2) 
In Equation 2, the coefficient c is a function of Mannings n value, the top width of the channel 
and the friction slope, data that are all site specific. Taking the logarithm of Equation 2 results in 
the following equation : 
log dT = log c + 0.6 (log QT). (3) 
For example, the 100-flood depth would be 
log d100 = log c + 0.6 (log Q100). (4) 
The equation for other recurrence interval floods would be similar to Equation 4. The difference 
in depth between the 100- and 2-year floods, for example, can be written as (where log c cancels 
out in the subtraction): 
log d100 - log d2 = 0.6[log Q100 - log Q2]. (5) 
Using Equation 1 to define [log Q100 - log Q2], Equation 5 can be rewritten as (note that log Qbar 
cancels out in the subtraction): 
log d100 - log d2 = 0.6 [(K100  K2) SlogQ ]. (6) 
Equation 6 can be rewritten in the more generic form 
log dT = log d100 - 0.6 [(K100  KT) SlogQ ]. (7) 
The KT values in Equation 7 can be obtained from Appendix 3 in Bulletin 17B for various values 
of skewness (G) or approximated from the following equation given in Appendix 3 of Bulletin 
17B: 
KT = 2/G {[(Kn,T  G/6) G/6 +1]3 1} (8) 

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where G is the coefficient of skewness of the logarithms of the annual maximum peak discharges 
and Kn,T is the standard normal deviate for recurrence interval T or the K value for zero skew. 
The above equation is not defined for G=0, use Kn,T for zero skew. 
A simple alternative to using Equation 8 would be to always use zero skew and assume the 
logarithms of the annual maximum peak discharges are approximately normally distributed. 
This is a reasonable assumption since the average of the skew values for the Bulletin 17B skew 
map is approximately zero. 
Hardison (1974) developed a national map of skewness coefficients (G) for the USA. In so 
doing, he developed regional averages of the standard deviation (SlogQ ) and the skewness of the 
logarithms of annual peak discharges (G), variables needed in the right-hand side of Equation 7. 
Hardison (1974) used the major watershed boundaries shown in Figure 1 but in some cases his 
subdivision of the major regions did not agree with Figure 1. Hardison did not provide a figure 
with his report so Figure 1 is used as the best representation of Hardisons regions. 

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The boundaries given in Figure 1 are more subdivided than those given in Table 1 that follows. 
For example, only one value of regional standard deviation and skewness is given in Table 1 for 
Regions 2, 3, 5 and 6 although Hardison subdivided these regions. Hardisons values for the 
subregions of Regions 2, 3, 5, and 6 were simply averaged to give the single value in Table 1. 
The values in Table 1 illustrate regional differences across the USA. Note the average skewness 
of the 15 regions in Table 1 is about -.08 or very close to zero. 
The following table summarizes the regional average standard deviation (SlogQ) and skewness 
(G) of the logarithms of annual peak discharges for major watersheds in the USA. 
Table 1. Summary of regional values of standard deviation and skewness. 
Region (see 
Figure 1) 
Average standard 
deviation (SlogQ) 
(log units) 
Average 
skewness (G) 
1A 0.222 0.382 
1B 0.247 0.517 
2 0.278 0.004 
3 0.241 -0.173 
4 0.199 -0.184 
5 0.326 -0.413 
6 0.326 -0.024 
7 0.338 -0.296 
8 0.418 -0.179 
9 0.224 -0.224 
10 0.278 -0.369 
11 0.426 -0.001 
12 0.183 -0.053 
13 0.200 -0.154 
14 0.211 0.134 
The values shown in Table 1 can be used to determine the KT values in Equation 7 that are 
needed to estimate log dT. The KT values are given in Appendix 3 of Bulletin 17B and are 
determined by entering this appendix with a recurrence interval (exceedance probability) and 
skewness or can be approximated from Equation 8. 
If zero skew (normal distribution) is assumed for the entire USA, then the KT values become, for 
example, Kn,2 = 0.0, Kn,5 = 0.84162, Kn,10 = 1.28155, Kn,25 = 1.75059, Kn,50 = 2.05375, Kn,100 = 
2.32635, and Kn,500 = 2.87816. (These are the Kn,T values in Equation 8.) Other values can be 
obtained from Appendix 3 using the column with skew = 0.0. The use of zero skew eliminates 
the need to use Appendix 3 of Bulletin 17B or Equation 8. 
The logarithm of the T-year depth (log dT) can be estimated from Equation 7 assuming the 100- 
year depth (d100) is known. Equation 8 can be used to estimate the KT values in Equation 7 or the 
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KT values for zero skew given above can be used as a simple alternative. The use of Equation 8 
with the average skewness (G) values in Table 1 is not much more difficult than using zero skew. 
REFERENCES 
Burkham, D. E., 1978, Accuracy of flood mapping: U.S. Geological Survey Journal of Research, 
Vol. 6, No. 4, pp. 515-527. 
Dunne, T. and Leopold, L. B., 1978, Water in environmental planning: W.H. Freeman and 
Company, San Francisco, CA, 818 p. 
Hardison, C. H., 1974, Generalized skew coefficients of annual floods in the United States and 
their application: Water Resources Research, Vol. 10, No. 4, pp. 745-752. 
Interagency Advisory Committee on Water Data, 1982, Guidelines for determining flood flow 
frequency: Bulletin 17B of the Hydrology Subcommittee, Office of Water Data Coordination, 
U.S. Geological Survey, Reston, Virginia, 183 p. 
Leopold, L. B. and Maddock, T., Jr., 1953, The hydraulic geometry of stream channels and some 
physiographic implications: U.S. Geological Survey Professional Paper 252, 57 p. 
Leopold, L. B., Wolman, M. G., and Miller, J. P., 1964, Fluvial processes in geomorphology: 
W.H. Freeman and Company, San Francisco, CA, 522 p. 
Thomas, D. M., 1964, Height-frequency relations for New Jersey floods: Article 167 in U.S. 
Geological Survey Professional Paper 475-D, pp. D202-203. 

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