Resolution 152-2020 2
4
5
6
7
8
9 MONROE COUNTY,FLORIDA
10 MONROE COUNTY BOARD OF COUNTY COMMISSIONERS
I I RESOLUTION NO. 159 -2020
12
13 A RESOLUTION OF THE MONROE COUNTY BOARD OF
14 COUNTY COMMISSIONERS ADOPTING FEMA TECHNICAL
15 BULLETIN 5 "FREE-OF-OBSTRUCTION REQUIREMENTS"
16 DATED MARCH 2020 AS REQUIRED PURSUANT TO MONROE
17 COUNTY CODE SECTION 122-2(C)
18
19
20 WHEREAS, Monroe County is currently a participating community in the National
21 Flood Insurance Program (NFIP) and is working on internal County policies to improve upon its
22 interpretation of NFIP regulations;and
23
24 WHEREAS, Monroe County desires to maintain eligibility and improve its standing in
25 FEMA's Community Rating System(CRS); and
26
27 WHEREAS, Monroe County Code Section 122-2(c), in part, requires that in interpreting
28 other provisions of this chapter, the building official shall be guided by the current edition of
29 FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical bulletins as
30 adopted by resolution from time to time by the Board of County Commissioners;
31
32 NOW, THEREFORE, BE IT RESOLVED BY THE BOARD OF COUNTY
33 COMMISSIONERS OF MONROE COUNTY,FLORIDA:
34
35 Section I. Pursuant to Monroe County Code Section 122-2(c), the Board hereby adopts
36 FEMA Technical Bulletin 5 "Free-of-Obstruction Requirements" dated March 2020, a copy of
37 which is attached hereto.
38
39 _ _ Section 2. The Clerk of the Board is hereby directed to forward one(I)certified copy of
40 this Resolution to the Building Department.
41
42
43
44
45
I PASSED AND ADOPTED by the Board of County Commissioners of Monroe County,
2 Florida,at a regular meeting held on the 17'h of June,2020.
3
4
5
6 Mayor Heather Carruthers Yes
7 Mayor pro tem Michelle Coldiron Yes
8 Commissioner Craig Cates Yes
9 Commissioner Sylvia Murphy Yes
10 Commissioner David Rice Yes
11
12
13
14 BOARD OF COUNTY COMMISSIONERS
15 OF MONROE CO , TY, FLORIDA
16
17 BY:
18 Mayor eat r arruthers
19
20 (SEAL)
21 ATTEST: KEV MADOK, CLERK
22
23
24 As Deputy Clerk
COUNTY ATTORNEY
Mt
T.W1 STEV
ASasTKNT CW1E17Y d e
Dote (off
o
C [
-n
N
-
3 0
O
F ,
o .
n
a,
t
M
m*
IN GARAGE-
«
Free - of- s ruc ion
9
Requirements
For Buildings Located in Coastal High Hazard Areas
in Accordance with the National Flood Insurance
Program
NFIP Technical Bulletin 5 / March 2020
ynxrM
����� FEMA
,LAND SECJ,
Comments on the Technical Bulletins should be directed to:
DHS/FEMA
Federal Insurance and Mitigation Administration (FIMA) Risk Management Directorate
Building Science Branch
400 C Street, S.W., Sixth Floor
Washington, DC 20472-3020
NFIP Technical Bulletin 5 (2020) replaces NFIP Technical Bulletin 5 (2008), Free-of-Obstruction
Requirements.
Cover photograph: Area beneath an elevated building that is free of obstruction.
NFIP Technical Bulletin 5 contains information that is proprietary to and copyrighted by the American
Society of Civil Engineers and information that is proprietary to and copyrighted by the International Code
Council, Inc. All information is used with permission.
For more information, see the FEMA Building Science
Frequently Asked Questions website at http://www.fema.gov/ To order publications, contact the FEMA
frequently-asked-questions-building-science. Distribution Center:
Call: 1-800-480-2520
If you have any additional questions on FEMA Building (Monday—Friday, 8 a.m.-5 p.m., EST)
Science Publications, contact the helpline at FEMA- Fax: 719-948-9724
Buildingsciencehelp@fema.dhs.gov or 866-927-2104. Email: FEMApubs@gpo.gov
You may also sign up for the FEMA Building Science email Additional FEMA documents can be found
subscription, which is updated with publication releases in the FEMA Library at
and FEMA Building Science activities. Subscribe at htt s: https://www.fema.gov/media-library,/
service.govdelivery.com/accounts/USDHSFEMA/subscribers resources.
new?topic id=USDHSFEMA 193.
Please scan this QR code
Visit the Building Science Branch of the Risk Management to visit the FEMA Building .
Directorate at FEMA's Federal Insurance and Mitigation Science web page.
Administration at https://www.fema.gov/building-science. ❑,
Table of Contents
Acronyms.............................................................................................................................................................iv
1 Introduction .....................................................................................................................................................I
2 National Flood Insurance Program Regulations..............................................................................................I
3 Building Codes and Standards ........................................................................................................................6
3.1 International Residential Code.............................................................................................................7
3.2 International Building Code and ASCE 24..........................................................................................9
4 NAP Flood Insurance Implications................................................................................................................13
5 Free-of-Obstruction Requirement Considerations ........................................................................................14
6 Building Elements Below the Base Flood Elevation.......................................................................................15
6.1 Access Stairs and Ramps......................................................................................................................15
6.2 Decks, Porches, and Patios ..................................................................................................................18
6.3 Elevators................................................................................................................................................19
6.4 Enclosed Areas.....................................................................................................................................19
6.5 Mechanical, Electrical, and Plumbing Equipment, Ducts, Tanks, and Fixtures .............................26
6.6 Foundation Bracing.............................................................................................................................28
6.7 Grade Beams ........................................................................................................................................30
6.8 Shcar Walls ...........................................................................................................................................30
6.9 Slabs ......................................................................................................................................................32
7 Site Development: Practices and Issues.......................................................................................................35
7.1 Accessory Storage Structures...............................................................................................................35
7.2 Detached Garages................................................................................................................................36
7.3 Erosion Control Structures..................................................................................................................37
7.4 Fences and Privacy Walls .....................................................................................................................38
7.5 Fill..........................................................................................................................................................39
7.6 Ground Elevations At or Above the Base Flood Elevation................................................................43
7.7 On-Site Septic Systems.........................................................................................................................43
7.8 Restroom Buildings and Comfort Stations ........................................................................................44
7.9 Swimming Pools and Spas...................................................................................................................44
8 References ....................................................................................................................................................46
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 i
List of Figures
Figure 1: Damage to an elevated building as a result of stairs that not break away cleanly.....................16
Figure 2: Open stairs,which minimize transfer of flood and wave forces.................................................17
Figure 3: Massive stairs attached to an elevated coastal home,which act as an obstruction....................17
Figure 4: Compliant wood slats installed flat against foundation pilings..................................................21
Figure 5: Compliant, fixed,wood louvers installed between pilings..........................................................21
Figure 6: Determination of the percentage of open area for a lattice or louver wall................................22
Figure 7: Breakaway wall that did not break away,which led to wave runup and contributed to
flood damage on the side of the elevated building.....................................................................22
Figure 8: Above-grade enclosure..................................................................................................................23
Figure 9: Above-grade enclosure floor system attached to building foundation......................................24
Figure 10: Above-grade enclosure supported by independent foundation.................................................24
Figure 11: Two-level enclosure........................................................................................................................25
Figure 12: Two-level enclosure schematic......................................................................................................26
Figure 13: Utilities mounted on wall,which prevented the wall from breaking away cleanly....................27
Figure 14: Floating debris trapped by metal rod cross bracing....................................................................29
Figure15: Knee bracing..................................................................................................................................29
Figure 16: Cross bracing that interfered with the failure of a breakaway wall............................................29
Figure 17: Grade beams that were exposed to flood forces during hurricane-induced scour;
grade beams must resist flood,wave, and debris loads when undermined...............................30
Figure 18: High-rise buildings elevated on shore-perpendicular shear walls..............................................31
Figure 19: Failure of a shore-perpendicular solid foundation wall that supported a low-rise
building,which resulted in failure of the beam and floor system that were supported
bythe shore-perpendicular wall...................................................................................................32
Figure 20: Damage to building foundation caused in part by failure of the reinforced slab
underminedby erosion.................................................................................................................33
Figure 21: Unreinforced slab that broke apart without imposing loads on the foundation.......................33
Figure 22: Example of frangible slab design..................................................................................................34
Figure 23: Small accessory structure that was moved by flood and wind forces .........................................36
Figure 24: Wave runup and overtopping at an erosion control structure....................................................37
Figure 25: Shore-parallel timbers attached to a pile foundation that were intended to act as a
bulkhead but constituted an obstruction and are not permitted...............................................38
Figure 26: Shore-perpendicular reinforced masonry privacy wall that collapsed into the
foundation of an adjacent building and contributed to failure of the corner
foundation piling and pile cap/beam..........................................................................................39
ii NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Figure 27: Post-hurricane photo showing an elevated building surrounded by gently sloping fill
and an adjacent, damaged, older, non-elevated building...........................................................41
Figure 28: Failure of two piles supporting an elevated deck that was likely caused by movement of
aspa................................................................................................................................................45
List of Tables
Table 1: Comparison of Selected 2018 IRC Requirements and NFIP Requirements................................7
Table 2: Comparison of Selected 2018 IBC and ASCE 24-14 Requirements with
NFIPRequirements.......................................................................................................................10
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 iii
Acronyms
ASCE American Society of Civil Engineers
BFE base flood elevation
CFR Code of Federal Regulations
DFE design flood elevation
DHS Department of Homeland Security
FEMA Federal Emergency Management Agency
FIRM Flood Insurance Rate Map
IBC International Building Code°
ICC International Code Council®
I-Codes International Codes®
IRC International Residential Code®
ISPSC International Swimming Pool and Spa Code°
NFIP National Flood Insurance Program
PFD primary frontal dune
SEI Structural Engineering Institute
SFHA Special Flood Hazard Area
iv NFIP TECHNICAL BULLETIN 5 MARCH 2O20
1 Introduction
This Technical Bulletin provides guidance on the
National Flood Insurance Program (NFIP) free-of- NFIP TECHNICAL BULLETIN 0
obstruction requirements in Coastal High Hazard NFIP Technical Bulletin 0, User's Guide
Areas, which are designated as Zone V (V, VE, V1-30, to Technical Bulletins, should be used
and/or VO) on a community's Flood Insurance Rate as a reference in conjunction with this
Map (FIRM), as well as the NFIP requirements for Technical Bulletin. Technical Bulletin 0
construction in Zone V to minimize flood damage describes the purpose and use of the
potential that is applicable to construction in Zone V. Technical Bulletins, includes common
The free-of-obstruction requirements were instituted concepts and terms, lists useful
to minimize the transfer of flood forces to an elevated resources, and includes a crosswalk
building's foundation and also to minimize the diversion of the sections of the NFIP regulations
or deflection of floodwater or waves that could damage identifying the Technical Bulletin that
the elevated building or neighboring buildings. addresses each section of the regulations
and a subject index.
This Technical Bulletin also discusses how the presence
or absence of obstructions can affect NFIP flood Readers are cautioned that the definitions
insurance premiums.
of some of the terms that are used in
the Technical Bulletins are not the same
Coastal waves and flooding can exert strong when used by the NFIP for the purpose of
hydrodynamic forces on building elements in their rating flood insurance policies.
path. Therefore, the NFIP requires that all new and
Substantially Improved structures in Coastal High
Hazard Areas (Zone V) be elevated on pilings or columns with the bottom of the lowest horizontal
structural members of the lowest floor elevated to or above the base flood elevation (BFE). These open
foundations allow floodwater and waves to pass beneath the elevated structure.
EFFECTS OF OBSTRUCTIONS
The NFIP requires the area beneath elevated structures in Zone V to remain free of any obstructions that
would prevent the free flow of coastal floodwater and waves during a base flood event. An area beneath a
structure elevated on an open foundation is considered to be free of obstructions if flood flow and waves
can pass through the area without significant flow diversion, wave reflection, or wave runup.
• Flow diversion. Change in the course of flood flow when it encounters an object or structure.
Diversion can be accompanied by an increase in the local flood level and/or flood velocity when the
blockage is large relative to the area through which the flow would otherwise pass.
• Wave reflection. Return or redirection of a wave striking an object.
• Wave runup. Rush of water up a slope or structure following wave breaking.
Some flow diversion, wave reflection, and wave runup can occur even with open foundations, but if the
guidance in this Technical Bulletin is followed, the effects should be minimized during flood conditions up
to the base flood event.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 1
Any element constructed below the BFE that is attached to a building in Zone V is considered part of the
building and must meet the free-of-obstruction requirements.
Standard solid foundation walls, such as masonry, concrete, and wood-frame walls, are not permitted
in Zone V because they would obstruct flow and be at risk of damage from high-velocity flood forces.
In addition, solid foundations and other obstructions could cause wave runup or reflection or divert
floodwater into the elevated portion of the building or nearby buildings.
The NFIP interprets the free-of-obstruction requirements to apply to certain site development practices
that prevent the free flow of coastal floodwater and waves under or around buildings or increase flood
loads on nearby buildings. Construction elements outside the perimeter (footprint) of and not attached
to a coastal building (e.g., bulkheads, retaining walls, decks, swimming pools, accessory structures) and
site development practices (e.g., addition of fill) may alter the physical characteristics of flooding or
significantly increase wave or flood forces affecting nearby buildings. As part of the design certification
process for a building in Zone V, the registered design professional must consider the effects these
elements and practices will have on the building and on nearby buildings.
The NFIP requires buildings to be constructed using methods and materials that minimize the potential
for flood damage. Therefore, any construction element placed on a building site in Zone V (see Sections
6 and 7) has the potential to affect the building and nearby buildings,which must be taken into account.
In addition to potential wave and floodwater diversion effects, obstructions can break free and become
floodborne debris that may strike and damage other buildings.
The building elements and site development issues in regard to obstruction that are discussed in this
Technical Bulletin include:
Building elements below the BFE Site development: Practices and issues
• Access stairs and ramps • Accessory storage structures
• Decks, porches, and patios • Detached garages
• Elevators • Erosion control structures
• Enclosed areas • Fences and privacy walls
— Below elevated structures • Fill
— Above-grade (elevated) • Ground elevations at or above the BFE
— Two levels • On-site septic systems
• Equipment and tanks • Restroom buildings and comfort stations
• Foundation bracing • Swimming pools and spas
• Grade beams
• Shear walls
• Slabs
2 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Building elements and site development practices
that are not specifically prohibited by the NFIP NFIP TERMS USED
may be used as long as they will not adversely affect IN THIS TECHNICAL BULLETIN
other structures. However, some building elements . Special Flood Hazard Area (SFHA): Area
and site development practices may increase subject to flooding by the base flood
flood-related loading on the building where those (1-percent-an nual-chance flood) and shown
practices are proposed. In such cases, the building on FIRMs as Zone A or Zone V.
must be designed to withstand the additional . Zone A: Flood zones shown on FIRMs as
flood-related loading and the registered design Zone A, AE, Al-30, AH, AO, A99, and AR.
professional must provide the required Zone V
certification for the building. • Zone V: Flood zones shown on FIRMs as
Zone V, VE, V1-30, and VO.
Questions about free-of-obstruction requirements . Coastal High Hazard Area:Area shown on
should be directed to the appropriate local FIRMs and other flood hazard maps as Zone
official, NFIP State Coordinating Office, or V, VO, VE, or V1-30.
Federal Emergency Management Agency (FEMA)
Regional Office.
2 National Flood Insurance Program
Regulations
An important NFIP objective is protecting buildings constructed in Special Flood Hazard Areas (SFHAs)
from damage caused by flooding. The SFHA is the land area subject to flooding by the base flood. SFHAs
are shown on Flood Insurance Rate Maps (FIRMs) prepared by FEMA as Zones A and V. The base flood
is the flood that has a 1 percent chance of being equaled or exceeded in any given year (commonly called
the "100-year" flood).
The NFIP floodplain management regulations include minimum building design criteria that apply to:
• New construction
• Work determined to be Substantial Improvements such as improvements, alterations, and additions
• Repair of buildings determined to have incurred Substantial Damage
A defining characteristic of the NFIP regulations applicable in Zone V is the requirement for the lowest
horizontal structural member of the lowest floor to be elevated to or above the BFE. This requirement
applies to both residential and non-residential buildings. Furthermore, the area beneath elevated
structures must be free of obstructions that would prevent the free flow of coastal floodwater and waves
during a base flood event.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 3
ZONE V CERTIFICATION OF STRUCTURAL DESIGN AND METHODS OF CONSTRUCTION
The NFIP regulations require communities to ensure that construction meets Zone V requirements,
including the free-of-obstruction requirement. Registered professional engineers or architects must
develop or review structural designs, specifications, and plans for new construction and Substantial
Improvements and certify that designs and methods of construction are in accordance with the
accepted standards of practice. Building engineers and architects should consult with communities
on their certification requirements before starting design, and communities must obtain and retain
the certifications.
Satisfying the NFIP free-of-obstruction requirement is part of the certification. Local officials
should determine that construction and/or site plans show all proposed site improvement elements
described in this Technical Bulletin. The NFIP requires Zone V certification prior to construction.
The community must ensure that what is constructed is compliant; some jurisdictions may require
post-construction certification by the registered design professional.
See Technical Fact Sheet 1.5 in the Home Builder's Guide to Coastal Construction (FEMA P-499) (2010a)
for a discussion of Zone V certification requirements.
The NFIP regulations for Zone V construction are codified in Title 44 Code of Federal Regulations
(44 CFR) Part 60 Criteria for Land Management and Use. Specific to this Technical Bulletin,
Section 60.3(a)(3) of the NFIP regulations states:
If a proposed building site is in a flood-prone area, all new construction and substantial
improvements shall ... (iii) be constructed by methods and practices that minimize flood
damages ...
Section 60.3(e)(4) states that a community shall require (emphasis added):
... that all new construction and substantial improvements in Zones VI V30, VE, and also
Zone V if base flood elevation data is available, on the community's FIRM, are elevated on
pilings and columns so that (i) the bottom of the lowest horizontal structural member of
the lowest floor (excluding the pilings or columns) is elevated to or above the base flood
level; and (ii) the pile or column foundation and structure attached thereto is anchored to
resist flotation, collapse, and lateral movement due to the effects of wind and water loads
acting simultaneously on all building components. Water loading values used shall be those
associated with the base flood. Wind loading values used shall be those required by applicable
State or local building standards.A registered professional engineer or architect shall develop
or review the structural design, specifications and plans for the construction, and shall certify
that the design and methods of construction to be used are in accordance with accepted
standards of practice for meeting the provisions of paragraphs (e)(4)(i) and (ii) of this section.
Section 60.3(e)(5) further states that a community shall require (emphasis added):
... that all new construction and substantial improvements within Zones Vl V30, VE, and V
on the community's FIRM have the space below the lowest floor either free of obstruction
or constructed with non-supporting breakaway walls, open wood lattice-work, or insect
screening intended to collapse under wind and water loads without causing collapse,
4 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
displacement, or other structural damage to the elevated portion of the building or
supporting foundation system. For the purpose of this section, a breakaway wall shall have
a design safe loading resistance of not less than 10 and no more than 20 pounds per square
foot. Use of breakaway walls which exceed a design safe loading resistance of 20 pounds per
square foot (either by design or when so required by local or State codes) may be permitted
only if a registered professional engineer or architect certifies that the designs proposed meet
the following conditions: (i) Breakaway wall collapse shall result from a water load less than
that which would occur during the base flood; and (ii) The elevated portion of the building
and supporting foundation system shall not be subject to collapse, displacement, or other
structural damage due to the effects of wind and water loads acting simultaneously on all
building components (structural and non-structural).Water loading values used shall be those
associated with the base flood. Wind loading values used shall be those required by applicable
State or local building standards. Such enclosed space shall be useable solely for parking of
vehicles, building access, or storage.
Section 60.3(e)(6) states that a community shall"prohibit the use of fill for structural support of buildings
within Zones V1-30,VE, and V on the community's FIRM."
Section 60.3(e)(7) states that a community shall "prohibit man-made alteration of sand dunes and
mangrove stands within Zones V1-30, VE, and V on the community's FIRM which would increase
potential flood damage."
For more information on NFIP regulations, refer to the following for:
• Guidance on coastal construction in the Coastal Construction Manual(FEMA P-55) (2011) and in the
Home Builder's Guide to Coastal Construction (FEMA P-499) (2010a)
• Guidance on design considerations, buildings codes and regulations, and best practices for coastal
communities in Local Officials Guide for Coastal Construction (FEMA P-762) (2009)
• Guidance on the breakaway wall requirements of Section 60.3(e)(5) of the NFIP regulations in NFIP
Technical Bulletin 9,Design and Construction Guidance for Breakaway Walls Below Elevated Buildings
Located in Coastal High Hazard Areas
• Guidance on the requirement that building materials used below the BFE must meet the flood
damage-resistant materials requirement of Section 60.3(a)(3) of the NFIP regulations in NFIP
Technical Bulletin 2,Flood Damage-Resistant Materials Requirements for Buildings Located in Special Flood
Hazard Areas
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 5
NFIP REQUIREMENTS AND HIGHER REGULATORY STANDARDS
State and Local Requirements. State or local requirements that are more restrictive or stringent
than the minimum requirements of the NFIP take precedence. The Technical Bulletins and other FEMA
publications provide guidance on the minimum requirements of the NFIP and describe best practices.
Design professionals, builders, and property owners should contact local officials to determine whether
more restrictive provisions apply to buildings or sites in question. All other applicable requirements of the
state or local building codes must also be met for buildings in flood hazard areas.
Substantial Improvement and Substantial Damage. As part of issuing permits, local officials must
review not only proposals for new construction but also for work on existing buildings to determine
whether the work constitutes Substantial Improvement or repair of Substantial Damage. If the work is
determined to constitute Substantial Improvement or repair of Substantial Damage, the buildings must
be brought into compliance with NFIP requirements for new construction. Some communities modify the
definitions of Substantial Improvements and/or Substantial Damage to be more restrictive than the NFIP
minimum requirements. For more information on Substantial Improvement and Substantial Damage, see
FEMA P-758, Substantial Improvement/Substantial Damage Desk Reference (2010b), and
FEMA 213,Answers to Questions About Substantially Damaged/Substantially Damaged Buildings (2018a).
Higher Building Elevation Requirements. Some communities require that buildings be elevated above
the NFIP minimum requirements. The additional elevation is called freeboard. Design professionals,
builders, and property owners should check with local officials to determine whether a community has
freeboard requirements. References to building elevations in this Technical Bulletin should be construed
as references to the community's elevation requirement in areas where freeboard is required.
3 Building Codes and Standards
In addition to complying with the NFIP requirements,
all new construction, Substantial Improvements, I-CODES AND COASTAL A ZONES
and repair of Substantial Damage must comply with
The 2018 International Codes (I-Codes)
applicable building codes and standards that have been treat Coastal A Zones like Zone V if a
adopted by states and communities. Limit of Moderate Wave Action (LiMWA)
The International Codes® (I-Codes®), published by is delineated on FIRMs. If a community
the International Code Council® (ICC®), are a family designates an area as a Coastal A Zone
of codes that includes the International Residential through its building code or floodplain
Code® (IRC®), International Building Code® management regulations, buildings in that
(IBC®), International Existing Building Code® area are required to comply with the
(IEBC®), and codes that govern the installation of Zone V requirements for foundations,
including the free-of-obstruction
mechanical, plumbing, fuel gas service, and other requirement, with an exception that
aspects of building construction. FEMA has deemed permits filled stem wall foundations.
that the latest published editions of the I-Codes
meet or exceed NFIP requirements for buildings and Note: Per the I-Codes and ASCE 24-14,
structures in flood hazard areas. Excerpts of the flood breakaway walls in the Coastal A Zone and
Zone V must have flood openings.
6 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
provisions of the I-Codes are available on FEMXs Building Code Resource webpage (https://www.fcma.
gov/building-code-resources).
3.1 International Residential Code
The IRC applies to one- and two-family dwellings and
townhomes not more than three stories above grade IRC COMMENTARY
plane. The IRC's free-of-obstruction requirements ICC publishes companion commentary
are summarized in Table 1 and compared to NFIP for the IRC. Although not regulatory, the
requirements. commentary provides guidance that is
Table 1 refers to selected requirements of the 2018 IRC useful in complying with, interpreting, and
and notes changes from the 2015 and 2012 editions. enforcing the requirements of the code.
Table 1: Comparison of Selected 2018 IRC Requirements and NFIP Requirements
Summary of Selected 2018 IRC Requirements and Comparison
MChanges from 20151
Free of Section R322.3.3 Foundations. Equivalent to NFIP
obstruction Requires in Coastal High Hazard Areas(Zone V) and Coastal A Zones that 44 CFR§§60.3(e)(4)
areas below elevated buildings be either free of obstructions or constructed and (5), except that
of breakaway walls. In Coastal A Zones, filled stem wall foundations must be 2018 IRC applies
designed to resist flood loads, erosion, and scour. in both Zone V and
Change from 2015 to 2018 IRC: Changes to subsection numbering due to Coastal A Zones,
insertion of new subsections expanding requirements for 322.3.4, Concrete with an exception
slabs; R322.3.7, Stairways and ramps; and R322.3.8, Decks and porches. that permits stem
wall foundations in
Change from 2012 to 2015 IRC: Applies Zone V requirements in Coastal A Coastal A Zones.
Zone, if delineated, with an exception that permits stem wall foundations.
Use of fill Section R322.3.2 Elevation requirements [excerpt]. Equivalent to
Prohibits the use of fill for structural support in Coastal High Hazard Areas NFIP 44 CFR
(Zone V) and Coastal A Zones, while allowing minor quantities of nonstructural §60.3(e)(6), with
fill to be used for drainage and landscaping purposes under and around more specificity for
buildings and for support of parking slabs, pool decks, patios, and walkways. use of fill for specific,
Change from 2015 to 2018 IRC: No change. nonstructural
purposes.
Change from 2012 to 2015 IRC: No change.
Enclosed Section R322.3.5 Walls below design flood elevation. Exceeds NFIP
areas In Coastal High Hazard Areas(Zone V) and Coastal A Zones, (1) requires that 44 CFR§60.3(e)(5)
enclosures below elevated buildings be designed to break away under certain by specifying
wind and flood loads without damaging the elevated building or the building components that are
foundation and (2) prohibits mounting of electrical, mechanical, and plumbing not to be mounted
system components on breakaway walls or penetration of the breakaway on or penetrate
walls. through breakaway
Change from 2015 to 2018 IRC: No change. walls and by requiring
flood openings in
Change from 2012 to 2015 IRC: Clarifies that attachment or penetration breakaway walls.
by electrical, mechanical or plumbing systems to breakaway walls is not
permitted.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 7
Table 1: Comparison of Selected 2018 IRC Requirements and NFIP Requirements(continued)
Summary of Selected 2018 IRC Requirements and Comparison
Changes from 20151
Equipment Section R322.1.6 Protection of mechanical, plumbing, and electrical Equivalent to
and tanks systems. NFIP 44 CFR
Requires that new electrical, plumbing, and mechanical system elements, §60.3(a)(3)(iv) but
along with replacements due to Substantial Improvements, be elevated to the with more specificity:
design flood elevation (DFE) or if below the DFE, to be designed and installed components are not
to prevent water from entering or accumulating within the element and be able to be mounted on or
to withstand certain loads and stresses. penetrate through
Change from 2015 to 2018 IRC: No change. breakaway walls and
there are explicit
Change from 2012 to 2015 IRC: No change. requirements for
Section R322.3.7 Tanks. tanks.
Requires tanks to either be located underground or elevated to the DFE. When
located underground, tanks must be anchored to resist flotation, collapse,
and lateral movement during the base flood. If elevated, tanks must be on
platforms that are cantilevered or knee-braced against the building or on a
platform with a foundation that resists certain wind and flood loads.
Change from 2015 to 2018 IRC: No change.
Change from 2012 to 2015 IRC: Added requirements for tanks.
Concrete Section R322.3.4 Concrete slabs. Exceeds NFIP
slabs Requires that slabs used for parking, floors of enclosures, landings, decks, 44 CFR§60.3(e)(5)
walkways, patios, and similar uses that are beneath buildings or located such by specifying
that they could be undermined or displaced and could cause damage be requirements for
either(1)structurally independent of foundations and no more than 4 inches concrete slabs.
thick, have no turn-downed edges, have no reinforcing, and have isolation
joints at pilings and columns and control or construction joints in both
directions no more than 4 feet apart or(2)self-supporting and will remain
intact under base flood conditions, taking into account scour and erosion,
and have building foundations capable of resisting any added loads due to the
presence of the slabs.
Change from 2015 to 2018 IRC: Moved specifications for slabs from R322.3.3.
to separate subsection.
Change from 2012 to 2015 IRC: No change.
Swimming Section R326.1 [Swimming Pools,Spas and Hot Tubs] General. Exceeds NFIP
pools and Requires pools and spas to comply with the International Swimming Pool and 44 CFR§60.3(e)(5)
spas Spa Code®(ISPSC), which requires compliance with American Society of by specifying
Civil Engineers(ASCE)24. requirements for door
Change from 2015 to 2018 IRC: No change. at top of stairway.
Change from 2012 to 2015 IRC: Added requirement to comply with the ISPSC.
Building Section R322.3.6.1 Protection of building envelope. Exceeds NFIP
envelope Requires an exterior door at the top of stairs that provides access to the 44 CFR§60.3(e)(5)
building. by specifying
Change from 2015 to 2018 IRC: No change. requirements for door
at top of stairway.
Change from 2012 to 2015 IRC: Added requirement for door.
8 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Table 1: Comparison of Selected 2018 IRC Requirements and NFIP Requirements(continued)
Summary of Selected 2018 IRC Requirements and Comparison
Changes from 20151
Stairways Section R322.3.7 Stairways and ramps. Exceeds NFIP
and ramps Provides four options for stairs and ramps located below the lowest floor 44 CFR§60.3(e)(5)
elevation: (1) open or partially open risers and guards, (2) breakaway, by specifying
(3) retractable, or(4) designed to resist flood loads. In all cases, the area requirements for
below stairs and ramps must not be enclosed with walls unless the walls are stairways and ramps.
designed to break away.
Change from 2015 to 2018 IRC: New section for stairways and ramps
incorporating language from R322.3.3.
Decks and Section R322.3.8 Decks and porches. Exceeds NFIP
porches Requires attached decks and porches to meet lowest floor elevation 44 CFR§60.3(e)(5)
requirement and either have compliant foundations or be cantilevered from by specifying
or knee-braced to the building. Self-supporting decks and porches must be requirements for
designed to remain in place or break away and may be below the BFE if not decks and porches.
enclosed by solid walls(including breakaway walls).
Change from 2015 to 2018 IRC: New section for decks and porches
incorporating language from R322.3.3.
Elevators No explicit provisions; see free-of-obstruction requirement in the first row of Meets NFIP 44 CFR
and this table (Table 1). §60.3(e)(5), which
foundation has no specific
bracing requirements.
Used with permission from ICC.
3.2 International Building Code and ASCE 24
The flood provisions of the International Building
Code® (IBC®) meet or exceed the NFIP requirements IBC AND ASCE COMMENTARIES
for buildings largely through reference to the ASCE 24, ICC publishes companion commentary
Flood Resistant Design and Construction. The IBC applies to for the IBC, and ASCE publishes
all applicable buildings and structures. While primarily companion commentary for
used for buildings and structures other than dwellings ASCE 24. Although not regulatory, the
within the scope of the IRC, the IBC may be used to commentaries provide information and
design dwellings.ASCE 24 applies to structures subject to guidance that are useful in complying
building code requirements. The ASCE 24 requirements, with, interpreting, and enforcing
summarized in Table 2, are more specific than the NFIP requirements.
free-of-obstruction requirements.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 9
Table 2: Comparison of Selected 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements
Summary of Selected 1Comparison
Mand Changes from 2015124-05 Requirements
General 2018 IBC Section 1612.2 Design and construction. Exceeds NFIP 44 CFR
design Requires design and construction of buildings and structures located in §60.3(e) by referring
requirement Coastal High Hazard Areas(Zone V) and Coastal A Zones to comply with to ASCE 24, which has
Chapter 5 of ASCE 7 and ASCE 24. more specificity for some
Change from 2015 to 2018 IBC: No change except renumbering of section. foundation elements and
higher minimum building
Change from 2012 to 2015 IBC: Applies Coastal High Hazard Area elevations, and which
requirements in Coastal A Zones if delineated. requires meeting Zone V
design and construction
standards in Coastal A
Zones(which are not
defined in the NFIP).
Obstruction ASCE 24-14 Section 1.2 Definitions. The NFIP does not define
"Obstruction—Any object or structural component attached to a structure "obstruction."
below the DFE that can cause an increase in flood elevation, deflect
floodwaters, or transfer flood loads to any structure."The DFE in the
definition of obstruction is the Design Flood Elevation, which will be equal
to or higher than the BFE.
Change from ASCE 24-05: No change.
Free of ASCE 24-14 Section 4.5.1 Foundation Requirements, General. Equivalent to NFIP
obstruction . Applies to foundation systems in Coastal High Hazard Areas(Zone V) 44 CFR§60.3(e)(5).
and Coastal A Zones.
• Requires foundations to be designed to minimize forces acting on
foundations, to minimize damage to the foundations and the elevated
structures, and to adequately transfer all loads imposed on the
foundations and elevated structures to the supporting soils.
With the exception of certain bracing and shear walls, requires foundation
system to be free of obstructions that will restrict or eliminate free passage
of high-velocity flood waters and waves during design flood conditions.
Change from ASCE 24-05: No change.
10 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Table 2: Comparison of Selected 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements(continued)
Summary of Selected 1Comparison
Mand Changes from 2015124-05 Requirements
Use of fill 2018 IBC Section 1804.5 Grading and fill in flood hazard areas. Equivalent to NFIP
Specifies that fill is only allowed where constructed and placed to avoid 44 CFR§60.3(e)(6),
diversion of water and waves toward any building or structure. Where with more specificity for
allowed, fill is required to be stable under conditions of flooding, including use of fill for specific,
rapid rise and drawdown and wave action. nonstructural purposes.
Change from 2015 to 2018 IBC: Clarifies that fill where allowed must be
stable under conditions of flooding.
Change from 2012 to 2015 IBC: No change.
ASCE 24-14 Section 4.5.4 Use of Fill.
• Specifies that placement of nonstructural fill for minimal site grading and
landscaping and to meet local drainage requirements is permitted.
• Specifies that placement of nonstructural fill under and around a
structure for dune construction or reconstruction is permitted if an
engineering report documents that the fill will not result in wave runup,
ramping, or deflection of floodwaters that can cause damage to
structures.
Change from ASCE 24-05: Clarifies that an engineering report is
necessary to document the effect of fill, and the commentary clarifies
that the intent is to allow minor amounts of nonstructural fill for specific
purposes.
Enclosed ASCE 24-14 Section 4.6 Enclosed Areas Below Design Flood Exceeds NAP 44 CFR
areas Elevation. §60.3(e)(5) by requiring
Requires enclosed areas below DFE to be designed and constructed flood openings in
with breakaway walls, with flood openings in those walls, and requires breakaway walls and
stairways within the enclosed area to have an exterior door at the top of a door at the top
the stairs. of stairways within
Change from ASCE 24-05: Modified to refer to subsections for enclosures.
requirements and adds the requirement for an exterior door at the top of
the stairs.
ASCE 24-14 Section 4.6.1 Breakaway Walls.
Change from ASCE 24-05: No change.
ASCE 24-14 Section 4.6.2 Openings in Breakaway Walls.
Change from ASCE 24-05: Modified to require flood openings in
breakaway walls forming an enclosure.
Utilities and ASCE 24-14 Section 7.1 General. Exceeds NFIP 44 CFR
equipment Requires attendant utilities and equipment to be at or above specified §60.3(a)(3)(iv)with
elevations or be specifically designed, constructed, and installed to freeboard requirements
prevent floodwaters from entering or accumulating within components. for utility system
Change from ASCE 24-05: No change platforms and equipment
for most buildings.
Tanks ASCE 24-14 Section 9.7 Tanks. Exceeds NFIP 44 CFR
Requires tanks in Coastal High Hazard Areas(Zone V)and Coastal A Zones §60.3(a)(3)(iv)with
to be(1)elevated on platforms meeting certain requirements or(2) installed specificity for platforms
and anchored below the eroded ground surface. and requirements for
Change from ASCE 24-05: Consolidated requirements for tanks in tanks.
Section 9.7.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 11
Table 2: Comparison of Selected 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements(continued)
Summary of Selected 1Comparison
Mand Changes from 2015and 2012 IBC/ASCE 24-05
Slabs ASCE 24-14 Section 9.3 Concrete Slabs. Exceeds NFIP
Requires in Coastal High Hazard Areas(Zone V) and Coastal A Zones 44 CFR§60.3(e)(5)
that concrete slabs be either(1) designed as frangible, not structurally with requirements for
connected to structure, and not capable of creating debris that would concrete slabs.
cause significant damage to other structures or(2) be self-supporting and
remain in place and functional after the design flood.
Change from ASCE 24-05: Slabs were moved from Section 4.8 to Section
9.3. New text permits(non-building-foundation)self-supporting structural
slabs for parking/enclosure/deck/patio in Zone V and Coastal A Zone.
Swimming 2018 IBC Section 3109.1 General. Exceeds NFIP
pools and Requires, within Coastal High Hazard Areas(Zone V) and Coastal A 44 CFR§60.3(e)(5)
spas Zones, that the design and construction of swimming pools, spas, and with requirements for
hot tubs comply with the ISPSC, which requires pools to be designed in swimming pools and
accordance with ASCE 24. spas.
Change from 2015 to 2018 IBC: No change
Change from 2012 to 2015 IBC: Replaces specific requirements with
reference to the ISPSC.
ASCE 24-14 Section 9.6.2 Pools in Coastal High Hazard Areas,
Coastal A Zones and Other Flood Hazard Areas.
Requires pools to be(1) elevated, (2) designed to break away without
producing damaging debris, or(3) designed to remain in the ground
without obstructing flow that could cause damage. Pools must be
structurally independent of buildings and structures unless located in or
on elevated floors or roofs that are above the DFE.
Change from ASCE 24-05: Clarifies pool requirements for pools within
Coastal High Hazard Areas, Coastal A Zones, and other flood hazard
zones.
Elevators 2018 IBC Section 3001.3 Referenced standards. Exceeds NFIP
Requires the design, construction, installation, alteration, repair, and 44 CFR§60.3(e)(5)
maintenance of elevators and conveying systems and their components with requirements for
to comply with the standard specified in 2018 IBC Section 3001.3, elevators.
Table 3001.3, and ASCE 24 unless the code states otherwise.
Change from 2015 to 2018 IBC: Standards moved to Table 3001.3.
Change from 2012 to 2015 IBC: No change.
Access ASCE 24-14 Section 8.1 General. Exceeds NFIP
stairs and In Coastal High Hazard Areas(Zone V) and Coastal A Zones provides four 44 CFR§60.3(e)(5)
ramps options for the design and construction of stairways and ramps below the with requirements and
required elevation. alternatives for stairways
Change from ASCE 24-05:Adds option for retractable stairways and and ramps.
ramps.
12 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Table 2: Comparison of Selected 2018 IBC and ASCE 24-14 Requirements with NFIP Requirements(continued)
Summary of Selected 1Comparison
Mand Changes from 2015124-05 Requirements
Decks and ASCE 24-14 Section 9.2 Decks and Porches Exceeds NFIP
porches 9.2.1 Attached Decks and Porches. 44 CFR§60.3(e)(5)with
In coastal high hazard areas (Zone V) and Coastal A Zones, specifies requirements for decks
that attached decks and porches be elevated on certain foundations or and porches.
cantilevered from the main structure.
ASCE 24-14 Section 9.2.2 Detached Decks and Porches.
In Coastal High Hazard Areas (Zone V) and Coastal A Zones, specifies that
detached decks and porches be(1) designed and constructed to remain
intact and in place during the base flood or(2) be designed to be frangible,
minimizing debris capable of causing significant damage to any structure.
Change from ASCE 24-05: Clarifications with no new requirements or
limitations.
Foundation ASCE 24-14 Section 4.5.11 Bracing. Exceeds NFIP
bracing Change from ASCE 24-05: No change. 44 CFR§60.3(e)(5)with
requirements for bracing.
Used with permission from ASCE and ICC.
4 NFIP Flood Insurance Implications
Meeting the minimum NFIP floodplain management
requirements does not necessarily result in the EFFECT OF CONSTRUCTION
lowest NFIP flood insurance premium. NFIP flood BELOW THE BFE
insurance premiums depend on the presence, location, Any construction or site development
construction, size, age, and use of enclosures and other practice below the BFE (even piles
building components and equipment. Floodplain and columns permitted by the NFIP)
management regulations allow enclosures greater than will cause a localized disruption of
300 square feet, but structures with these enclosures flow and waves during the base flood.
have higher NFIP flood insurance premiums. Designers The question is whether the localized
should consult a qualified insurance agent and review disruption will be great enough to harm
FEMA's NFIP Flood Insurance Manual to determine the elevated building or surrounding
insurance implications of design and construction buildings.
decisions.
NFIP floodplain management regulations allow certain
construction elements below the BFE that may or may not break away during the base flood (e.g.,
stairwells, elevator shafts, shear walls). These elements may or may not be considered obstructions for
NFIP flood insurance rating purposes. For example:
• The NFIP floodplain management regulations in 44 CFR§ 60.3(e) allow open wood lattice, insect
screening, and solid, non-load-bearing, breakaway walls below elevated buildings in Coastal High
Hazard Areas. Even though floodplain management regulations permit solid breakaway walls, garage
doors, and slats or lattice (with less than 40 percent of the area open), building designers and owners
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 13
should be aware that these elements can result in
higher NFIP flood insurance premiums. See the text DETERMINING FLOOD INSURANCE
box"NFIP Flood Insurance Free-of-Obstruction IMPLICATIONS BEFORE THE DESIGN
Rate" below for details. Design professionals and property
• The NFIP floodplain management regulations in owners may wish to contact a qualified
44 CFR§ 60.3(e) restrict uses of space below the BFE insurance agent or the NFIP regarding
the flood insurance rating and premium
to parking of vehicles, building access, and storage.
implications of obstructions before a
Stairs, ramps, and elevators are permitted. However, building is designed.
depending on how stairs, ramps, and elevators are
constructed, they may be considered obstructions
for NFIP flood insurance rating purposes and could
result in higher premiums.
NFIP FLOOD INSURANCE FREE-OF-OBSTRUCTION RATE
In order for a structure to qualify for the NFIP flood insurance free-of-obstruction rate, the space below
the lowest elevated floor must be free of obstructions with the following exceptions:
• Insect screening provided that no additional supports are required for the screening
• Wooden or plastic lattice with at least 40 percent of its area open and constructed of material no
thicker than inch
• Wooden or plastic slats or shutters with at least 40 percent of their area open and constructed of
material no thicker than 1 inch
• One solid breakaway wall or garage door with the remaining sides of the enclosure constructed of the
above-mentioned insect screening, wooden or plastic lattice, slats, or shutters
5 Free-of-Obstruction Requirement
Considerations
Some NFIP flood-resistant design and construction requirements, including free-of-obstruction
requirements, are performance related and are not prescriptive. In other words, the expected building
performance is stated, but how to achieve the performance is not specified. It is up to the design
professional to create a design that complies with the free-of-obstruction performance requirements and
up to the local official to determine whether the design satisfies the community's requirements.
It is not always clear whether a particular building element or a site development practice would create
a significant obstruction that would prevent the free passage of floodwater and waves. "Significant" is
used because any construction element or site development practice below the flood level would cause a
localized disruption of flow and waves during the base flood. Determining whether the disruption would
be significant is not always easy because in most cases, there are no analytical or readily usable numerical
14 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
tools to answer the question with certainty. Local experience, results of post-disaster assessments, and
application of coastal processes and building science principles must be relied on to reach a conclusion.
Some local floodplain management regulations require potential obstructions below or near a building
to be evaluated to determine their effects on flow and waves. Fluid mechanics and coastal engineering
references, such as the U.S. Army Corps of Engineers Coastal Engineering Manual (2002), provide some
guidance,but the methods in these references are not generally capable of evaluating the potential effects
of small building elements or small amounts of fill on flooding and waves during a base flood. Numerical
coastal storm surge and wave models used in Flood Insurance Studies do not have sufficiently detailed
resolution to discern building-sized disruptions to flow and wave fields.
Currently, developing models with fine enough resolution is technically challenging, time consuming, and
cost prohibitive.And although recently developed,sophisticated numerical models show some promise in
analyzing flow around buildings, their use is not economically feasible for most communities, owners, or
designers interested in examining the potential obstructions discussed in this Technical Bulletin.
6 Building Elements Below
the Base Flood Elevation
This section discusses common building elements under elevated buildings that can impede the free
passage of flood flow and waves. Following the guidance in this section will minimize potential obstructive
effects and satisfy the NFIP free-of-obstruction requirement.
6.1 Access Stairs and Ramps
Access stairs and ramps that are attached to or beneath an elevated building may be enclosed with
breakaway walls or unenclosed. However, like foundation bracing (see Section 6.8), stairs and ramps can
impede breakaway walls from breaking away cleanly as intended. To minimize this possibility,unenclosed
stairs and ramps are preferred, but if enclosures are used, the design should be such that the stairs and
ENTRY DOOR AT TOP OF ACCESS STAIRS
Access stairs to elevated buildings are often constructed inside a breakaway enclosure with an entry
door at the bottom of the enclosure but no entry door into the building at the top of the stairs. The lack of
an entry door at the top results in a large opening in the building envelope when enclosures break away.
Numerous post-disaster damage assessments have shown that loss of breakaway enclosures exposes
building interiors to higher internal wind pressures and wind-driven rain. Loss of breakaway enclosures
can also provide an easy path for floodwater to enter buildings, resulting in damage that can be avoided
when doors are provided at the top of the access stairs.
Beginning with the 2015 IRC and ASCE 24-14, solid entry doors capable of resisting all design loads are
required to be installed at the top of access stairs inside breakaway enclosures.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 15
ramps do not interfere with breakaway wall performance. Enclosing stairways also affects NFIP flood
insurance rates.
Stairs and ramps are not required to break away, but it is a design option. Stairs and ramps must be
designed and constructed to either:
• Resist flood loads and remain in place during floods up to and including the base flood. If this option
is selected, the elevated building and its foundation must be designed to resist any flood loads that are
transferred from the stairs or ramp to the building, or
• Break away during base flood conditions without causing damage to the building or its foundation.
Figure 1 shows an example of an elevated building that was damaged as a result of stairs that did not
break away cleanly; the stairway pulled out the exterior wall of the elevated building as the stairway failed.
Figure 1: hIN
Damage to an elevated
building as a result of stairs
that not break away cleanly
Constructing access stairs with open sides (open guards and railings) and risers, to the extent allowed
by building codes, minimizes the potential for flood loads acting on the stairs, thereby minimizing
flood damage and also minimizing transfer of flood loads to the elevated building. Open stairs should
be considered whenever possible (see Figure 2). Note that building codes may have maximum opening
size limits on stair risers and railings, necessitating a longer run. Check with the local jurisdiction for
requirements.
Ramps must be designed and constructed to minimize the obstruction of floodwater and waves and
configured so that floodwater and waves cannot flow directly up the ramp toward the elevated building.
This means that ramps should be positioned to avoid a straight alignment from the elevated building to
the likely direction of wave and surge approach.
16 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Figure 2:
- Open stairs, which minimize
IT m �° �1 � tT, , -��� transfer of flood and wave
forces
y ,
Massive exterior stairs are not permitted because they are inconsistent with the free-of-obstruction
requirement and because other types of stairs can provide access. Figure 3 shows massive stairs that are
attached to an elevated coastal home. These massive stairs will act as an obstruction and increase the
likelihood of trapping or reflecting waves and flood flow beneath the elevated building.
In some cases, life-safety code requirements dictate that stairs and stairwells in structures of certain
occupancy categories be constructed to be fire resistant and structurally stable even if portions of the
adjacent structure fail. Stairs and stairwells that meet these requirements are usually constructed of
some combination of steel, reinforced masonry, and reinforced concrete and will not break away under
Figure 3:
Massive stairs attached to
an elevated coastal home,
which act as an obstruction
yy
�.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 17
expected base flood loads and conditions. These stairs and stairwells, typically found in mid- and high-
rise buildings, must be designed to withstand all base flood loads, including flow, waves, and floodborne
debris impacts.
6.2 Decks, Porches, and Patios
Decks, porches, and patios are typically outside the footprint of elevated residential and commercial
buildings and may be constructed at grade, above grade but below the BFE,at the BFE, or above the BFE.
In Coastal High Hazard Areas, decks and porches outside the building footprint must meet one of the
following conditions:
• If structurally attached to a structure, the bottom of the lowest horizontal structural member of the
deck or porch must be at or above the BFE. Deck and porch supports that extend below the BFE (e.g.,
pilings, bracing) must comply with Zone V design and construction requirements, and the structure
must be designed to accommodate any increased loads resulting from the attached deck or porch.
• If an attached deck or porch is located above the BFE but relies on support elements (posts, columns,
braces) that extend below the BFE, the supports must comply with Zone V design and construction
requirements.
• If a deck,porch, or patio (not counting its supports) lies in whole or in part below the BFE, it must be
structurally independent from the structure and its foundation system.
Decks that are constructed within the building footprint between the ground and the elevated building
are sometimes referred to as mezzanine decks. In Coastal High Hazard Areas,mezzanine decks should be
treated similar to the floors of above-grade (elevated) enclosures (see Section 6.5). If directly below the
footprint, a mezzanine deck that is structurally attached to the host building is treated as the lowest floor
elevation for NFIP flood insurance rating purposes.
From a floodplain management perspective, mezzanine decks must meet building code requirements for
dead,live, and other applicable loads and must be designed to either:
1) Break apart into small pieces without causing collapse, displacement, or other structural damage
to the elevated building or the supporting foundation under flood loads less than those that occur
during the base flood or
2) Along with the building foundation, accommodate flood loads transferred from the mezzanine deck
to the building foundation during flooding up to and including base flood conditions.
Mezzanine decks may be independently supported on an open foundation and must be designed to either
withstand flooding up to and including the base flood or break apart into small pieces under base flood
or lesser conditions. Structurally independent decks below the BFE and below a structure's footprint are
not considered the lowest floor for NFIP flood insurance purposes.
Decks, porches, and patios must not adversely affect the structure with which they are associated, or
nearby structures, by diverting floodwater and waves during flood conditions up to and including the
base flood. Some decks and patios, such as low-profile decks and patios constructed at natural grade
or on minor quantities of fill necessary to level the site (see the textbox in Section 7.5), are deemed to
comply by minimizing harmful diversion of floodwater or wave runup and reflection. A low-profile deck
or patio, as used here, has a floor system depth of 12 inches or less, some of which may be below the
18 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
adjacent finished grade. The depth does not include railings,which should be open to allow water to flow
through.Attaching seats,benches, tables, planters, or similar features will cause a deck or patio to lose its
deemed-to-comply low-profile classification. These features may or may not be obstructions (depending
on size, number, and configuration) and should be evaluated for potential effects on flow and waves.
Decks, porches, and patios must be designed and constructed so that when subject to flooding up to
and including base flood conditions, they do not create debris capable of causing significant damage to
nearby structures. This means that decks, porches, and patios must remain intact and in place during
base flood conditions or break apart into small pieces so the resulting debris does not lead to structural
damage to nearby structures.
Decks and porches that are structurally attached to structures in Zone V must be supported to resist the
simultaneous action of design wind loads and base flood loads. Most attached decks and porches are
supported on piles or columns embedded in the ground and are capable of surviving anticipated erosion
and scour. Post-storm assessments frequently identify decks and porches that were elevated on posts whose
diameters were too small or on structural elements without sufficient embedment into the ground. The
result of inadequate support is loss of decks and porches and sometimes damage to elevated structures.
Unless the building code or local community prescribes otherwise, the foundation for an elevated deck or
porch attached to a structure in Zone V should be similar to the structure's foundation. Attached decks
and porches may be cantilevered from main structures instead of supported on piles or columns.
6.3 Elevators
Elevators attached to or beneath elevated structures
in Zone V must comply with building, fire, electrical, NFIP FLOOD INSURANCE
and mechanical code requirements. Elevators and AND ELEVATOR SHAFTS
elevator shafts are not required to break away but AND ELEVATOR EQUIPMENT
must meet flood damage-resistant material and Elevator shafts and elevator equipment
equipment requirements. below the BFE will result in higher NFIP
flood insurance premiums. The presence
Flood loads acting on elevator components, any non- of elevators always increases the
breakaway shaft walls, and potential wave runup and premium, regardless of how the shafts are
reflection effects must be accounted for in the design constructed.
of the elevated structure and its foundation system.
Therefore, it is advantageous to minimize the size of
elevators, especially residential elevators in one- and two-family structures. Elevators should be designed
and installed to satisfy the requirements of ASCE 24, which FEMA has determined meets or exceeds the
minimum NFIP requirements. Additional guidance can be found in NFIP Technical Bulletin 4, Elevator
Installation for Buildings Located in Special Flood Hazard Areas.
6.4 Enclosed Areas
The types of enclosed areas that are discussed in this section are:
• Enclosed areas below elevated structures
• Above grade (elevated) enclosures
• Two-level enclosures
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 19
6.4.1 Enclosed Areas Below Elevated Structures
The use of enclosed areas below elevated
structures is restricted to parking of vehicles, PRIVACY SCREENING
building access, and storage. Enclosed areas Privacy screening around outdoor shower areas is
must not be used for habitable purposes. permitted if the sides are open at top and bottom
Enclosed areas, including foyers, must and the screening will break away under base flood
be constructed of flood damage-resistant or lesser conditions. If a space under the building
materials and not be finished. All enclosed footprint is enclosed with privacy screening, there will
areas below elevated buildings will be be an NFIP flood insurance premium increase.
considered when the NFIP flood insurance
premium is determined.
The NFIP regulations in 44 CFR§ 60.3(e)(5) SIZE OF ENCLOSURES
state that the area beneath the elevated AND NFIP FLOOD INSURANCE
portion of a structure in Zone V may be The NFIP does not limit the size of enclosures under
enclosed only with open lattice, insect elevated structures. However, higher NFIP flood
screening, or non-supporting breakaway insurance premiums will generally be assessed for
walls (see NFIP Technical Bulletin 9, Design structures in Zone V with enclosed areas of any
and Construction Guidance for Breakaway size(including stairwells and elevator enclosures),
Walls Below Elevated Buildings in Coastal even if enclosed by breakaway walls. Annual NFIP
High Hazard Areas). However, while NFIP premiums can be even higher when buildings have
regulations permit all enclosure walls to be enclosures that are 300 square feet or larger. Some
solid breakaway walls, construction of such communities have adopted restrictions or prohibitions
will lead to a With-Obstruction rating by the on enclosures. Designers, contractors, and owners
NFIP. should check local requirements prior to construction.
FEMA guidance states that the following The NFIP does not require flood openings in the walls
lattice and slats are acceptable: of enclosures in Zone V. However, beginning with
ASCE 24-14 and the 2015 IRC and IBC, enclosures in
• Wood or plastic lattice no thicker than Zone V require flood openings.
1/inch with at least 40 percent of its area
open
• Wood or plastic slats or fixed louvers no thicker than 1 inch that,when installed, have at least
40 percent of their area open
Figure 4 and Figure 5 show examples of compliant slats,which are typically installed flat against foundation
pilings (see Figure 4) or angled like louvers between the pilings (see Figure 5). Percent open area of a
lattice or louver wall should be calculated based on the area through which water can flow through lattice
or louvers, divided by the total area of the enclosure wall (see Figure 6).
20 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
. °. Figure 4:
Compliant wood slats
installed flat against
foundation pilings
• 4.1 . .fir'i I d
`.xns.Yw,&Y xx,ffiIC�•,1p;llrYYf�:M1@itiCPa'�'=�"����■ �^(__
.. •_�`�Fsn7�. _ _-....::..:�.._.: '--" .tier.i °.-.ism�,..�.� ,^•.ikt� _ _ _sue °-.,.y. .--,. _' '.-
Figure 5:
Compliant,fixed,wood
louvers installed between
pilings
r
P
1
1
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 21
�{a Lattice wall
b Percent open area is the sum of all individual open areas, divided
by the overall panel area,times 100.
Measure the height and width of the opening, multiply by the total
number of openings, and divide by the total panel area (height
H times width).To get a percentage, multiply the result by 100.
%open area = F(ab)x 100
HW
I�W
I�w�l Louver wall
Te Percent open area is the sum of all individual
T open areas in gaps between louvers, plus top and
bottom edge opening areas, divided by the overall
panel area, times 100.
The individual open areas are calculated as the
H distance between louvers multiplied by the panel
width. Multiply that area by the total number of
gaps, add the edge opening areas, and divide by
g the total panel area (height times width). To get a
percentage, multiply the result by 100.
e�
open area = (F(gw) + (2ew))x 100
I�W HW
Figure 6: Determination of the percentage of open area for a lattice or louver wall
Figure 7 shows an elevated building in which a portion of a solid breakaway wall enclosure did not break
away. Waves were not able to pass beneath the elevated structure, and wave runup against the enclosure
wall likely caused damage above the elevated floor.
Figure 7: r
Breakaway wall that did not
break away, which led to
wave runup and contributed � rOIL
r
to flood damage on the side A"
of the elevated building � ;u
cqI
Not
I
22 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
6.4.2 Above-Grade Enclosed Areas (Elevated)
Another enclosure option is to construct enclosures with floor systems that are elevated above grade and
are not in contact with the ground (see Figure 8). Placing the enclosure floor above grade minimizes the
potential for damage to the enclosure and contents during frequent, low-level flood events.
Figure 8:
Above-grade enclosure
f �r
q
1
4
An above-grade enclosed area (sometimes referred to as a hanging enclosure) is any enclosure with its
floor system above grade. The enclosure may be supported by a foundation beneath the enclosure or by
the elevated building and/or building foundation. A hanging floor is the lowest floor elevation for NFIP
flood insurance rating purposes.
Above-grade enclosures may be used only for
storage and building access and must meet all other ABOVE-GRADE ENCLOSURES
requirements applicable to enclosures, including AND NFIP FLOOD INSURANCE
the use of breakaway walls and flood damage- NFIP flood insurance policies for elevated
resistant materials below the BFE. Additionally, buildings with above-grade enclosures are
mechanical and electrical systems in the enclosure rated assuming the floor of the above-grade
must be elevated to or above the BFE.A floor grate enclosure is the lowest floor(or based on the
should be installed in the enclosure floor, and elevation of the lowest horizontal structural
flood openings should be installed in breakaway member of the enclosure instead of the lowest
enclosure walls. The grate will reduce vertical horizontal structural member of the lowest floor
uplift (buoyancy) loads on the enclosure floor of the elevated building). Owners should ask
before water flows through the openings in the their insurance companies to submit requests
enclosure walls and allow the elevated enclosure to to the NFIP for a special rating for buildings
drain fully, reducing the downward load caused by with above-grade enclosures.
water that would otherwise be trapped above the
enclosure floor.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 23
The design of the foundation and enclosure
Elevated building
floor system for above-grade enclosures that
are in Zone V must meet one of the following Breakaway walls
conditions: Base flood
elevation (BFE)
— - - - - - - - - - - - - - - - - - - —
• The floor system is designed to break Pilings or
away under flood loads less than those columns
that occur during the base flood without Enclosure walls o
span causing collapse, displacement, or columns
or
other structural damage to the elevated Flood opening
building or the supporting foundation
Floor system
(see Figure 9), or attached to pilings
or columns See note
• The floor system is designed to remain Stairway not shown
in place and intact, and the building
foundation is designed to accommodate
flood loads transferred from the
enclosure floors stem to the foundation Note: Floor system designed to break away or foundation
y designed to accommodate flood loads transferred by
during flood conditions up to and non-breakaway floor system
including the base flood (see Figure 9),
or Figure 9:Above-grade enclosure floor system attached to building
foundation
• The enclosure floor system is
independently supported on an open
foundation (see Figure 10). Base flood elevation (BFE)
— - - - - - - - - - - - - - - -
Flood openings in above-grade enclosure
Breakaway wall
walls are required by the building code
but do not reduce NFIP flood insurance
premiums for the enclosure.
6.4.3 Two-Level Enclosed Areas
Flood opening Enclosure floor;
In flood hazard areas where the BFE is floor grate to
_ facilitate drainage
very high above the ground or where
No more No structural
owners elect to elevate buildings very than 1 foot connection to wall
high, some owners opt to build two-level wood-frame floor system
enclosures (see Figure 11 and Figure 12). Piers that
Two-level enclosures are permitted but not Pier support only
recommended due to their more complicated the enclosure
construction and increased potential for �� �` �` ;a �` �` �` :.a.. • �` �` �`
Exterior grade ;• I.;. a• ;• �. a•
TWO-LEVEL ENCLOSURES `Pier footings
Two-level enclosures are also known Figure 10:Above-grade enclosure supported by independent
as two-story enclosures, double foundation
enclosures, and stacked enclosures.
---------------------------------------------------------------------
24 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Figure 11:
o Two-level enclosure
i
5 -
R _
tl
j
floodborne debris. Two-level enclosures could also result in the floor of the upper level being considered
the lowest floor for NFIP flood insurance rating purposes.
Both levels of the enclosure must meet all of the floodplain management and building code requirements
for enclosed areas, including breakaway walls, elevated utilities, flood damage-resistant materials, and
limitations on use (parking of vehicles, building access, and storage). The floor system of the upper
enclosure level must be designed to meet one of the options for above-grade (elevated) enclosed areas
(see Section 6.4.2).
Openings with grates should be installed in the floor to facilitate drainage from the upper level enclosure.
In the event that floodwater enters the upper level but does not cause failure of the breakaway walls, the
floor grates will allow trapped water to drain to the lower level and not overload the upper level floor
system.
TWO-LEVEL ENCLOSURES AND NFIP FLOOD INSURANCE
Designers and owners should be aware that a building with a two-level enclosure, even if allowed
by permit, could result in higher NFIP flood insurance premiums than if the building has a one-level
enclosure. Even if a two-level enclosure complies with building code and floodplain management
requirements for enclosures, the upper floor of the two-level enclosure could be deemed the lowest floor
for NFIP flood insurance rating purposes (the lowest floor elevation for flood insurance purposes is the
first floor elevated above ground). Owners should ask their insurance companies to submit requests to
the NFIP for a special rating for buildings with two-level enclosures.
-----------------------------------------------------------------------------------------------------------
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 25
Figure 12:
Two-level enclosure schematic
Breakaway walls
around enclosure
Base flood ———— ———————————————
elevation (BFE)
Flood opening 30 Floor system
connected to
pilings/columns
(pilings/columns
No more not shown)
than 1 foot
UrIF
Floor grate
to facilitate
drainage
Breakaway walls
around enclosure
Flood opening
Interior
grade/floor
(frangible)
No more
than 1 foot
Exterior grade
6.5 Mechanical, Electrical, and Plumbing Equipment, Ducts,
Tanks, and Fixtures
Mechanical, electrical, and plumbing equipment,
ducts, tanks, and fixtures serving elevated buildings EQUIPMENT BELOW AN ELEVATED
are required to be elevated to or above the BFE or BUILDING AND NFIP FLOOD INSURANCE
protected from water entry during the base flood. Designers and owners should be aware that
There are exceptions for elevator equipment that elevator equipment and other equipment
cannot be elevated (see NFIP Technical Bulletin 4, below an elevated building will result in
Elevator Installation forBuildings Located in Special Flood higher NFIP flood insurance premiums, even
Hazard Areas, and ASCE 24). if the equipment is allowed by permit.
------------------------------------------------------------------------------
26 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Utility lines, pipes, risers, and chases may need to
extend below the BFE but should be installed to UTILITY CHASES
minimize potential damage from flooding (some For floodplain management and NFIP flood
utility companies place meters below the BFE so they insurance purposes, utility chases designed
can be easily accessed). The following help minimize to protect utility lines from freezing are
potential damage: not considered enclosures. Utility chases
• Utility lines, pipes, risers,and chases are not must be small and not allow access for a
allowed to be attached to or penetrate through person to enter the space(access panels for
breakaway walls (see Figure 13). servicing the lines are appropriate).
• Utility lines, pipes, risers,and chases should be Because a utility chase is not considered
an enclosure, it does not have to meet the
located on the sides of piles and columns that are requirement of breakaway walls, louvers, or
opposite the anticipated direction of flood flow open latticework; however, the chase may
and wave approach,where possible. be breakaway under flood conditions.
Fuel tanks and other tanks serving elevated buildings The utility chase must be constructed
and located under or adjacent to the buildings must of flood damage-resistant materials
be in-ground or elevated above the BFE. In both below the BFE, and the enclosed utility
cases, tanks should be anchored to prevent flotation lines must meet the requirement to be
or lateral movement during base flood conditions. watertight and capable of withstanding
Platforms supporting elevated tanks should resist flood loads(hydrostatic, hydrodynamic,
flooding up to and including base flood conditions. wave). Additionally, the portions of the utility
system located below the BFE and the utility
To satisfy free-of-obstruction requirements, above- chase should not be attached to, mounted
ground tanks must not be located beneath elevated on, pass through, or be located along
buildings or attached to elevated buildings below the breakaway walls.
BFE. This requirement also applies to permanently
Figure 13:
Utilities mounted on wall, which
prevented the wall from breaking
away cleanly
efiry y,
y
I
V'
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 27
installed fuel tanks for outdoor kitchens. Portable gas grills and associated propane fuel tanks and similar
devices for which building permits are not required are not subject to these requirements. However,
communities may have other fire and life-safety requirements that must be met. In addition, when
flooding is anticipated, owners should move portable grills and propane fuel tanks to a safe location
where they will not pose a hazard or become floodborne debris.
Additional guidance can be found in FEMA P-348, Protecting Building Utilities from Flood Damage (2017),
and FEMA P-259,Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures (2012).
6.6 Foundation Bracing
Foundation bracing is often used to stiffen pile foundations and/or improve comfort and reduce sway in
elevated buildings. However, foundation designs without bracing are preferred in coastal areas because
they minimize obstructions to flow and waves.
Free-of-obstruction considerations call for using only the minimum amount of foundation bracing
necessary to achieve a stable design, and such bracing should be designed to withstand flood conditions
up to and including the base flood. Additional bracing may be used to improve the comfort of building
occupants (i.e., reduce building sway under non-flood conditions), but the additional bracing should not
be as strong as that required for structural stability and should not be relied on to yield a stable design, as
it may be lost during a flood.
Many coastal construction experts and design references advise relying on shore-perpendicular bracing
and minimizing the use of shore-parallel bracing. However,because wind and seismic loads can act in any
direction, this alternative may not always provide the structural stability that is required in some locations.
Increasing the number of piles (by decreasing horizontal spacing), detailing moment connections at the
tops of the piles (in the case of concrete piles and beams), and using grade beams are accepted ways
of eliminating or reducing the need for foundation bracing. Designers may determine other ways to
minimize the amount and type of bracing.
Diagonal timber cross-bracing is the most common type of bracing used on foundations under coastal
homes. Unfortunately, timber braces frequently fail during severe flood events as a result of wave or debris
impacts. If they survive, they can interfere with breakaway wall failure, trap debris, and transfer lateral
flood loads to the foundation. Metal rod braces, while less susceptible to failure, can also trap floating
debris (see Figure 14). Knee braces at the tops of pilings are sometimes preferred (Figure 15) because
their position higher up on the pilings will present less obstruction to flow and waves.
When foundation bracing below the BFE is used,it must be placed so as not to interfere with the intended
failure of breakaway wall panels (see Figure 16).Avoiding interference may require eliminating breakaway
walls, shifting the location of breakaway walls, or redesigning the foundation so the need for certain
braces is eliminated. Breakaway walls and foundation bracing should not be placed close to each other if
either could adversely affect the intended performance of the other.
28 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
R Figure 14:
" Floating debris trapped by metal rod
l K cross bracing
"V
y g xr
pa ,
a
y
1 f'• � of
— l
Figure 15: Knee bracing Figure 16: Cross bracing that interfered with the
failure of a breakaway wall
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 29
6.7 Grade Beams
Grade beams are horizontal elements at or below the ground surface that tie the foundation piles or
columns together and provide additional lateral support. They are typically reinforced concrete or wood.
Grade beams that are placed with their upper surfaces flush with or below the natural grade (the grade
before the site is altered by fill or grading, if any) are not considered obstructions and are allowed by
NFIP. However,storm erosion and local scour can expose and undermine grade beams,sometimes leaving
them suspended above the post-storm ground profile. Designers must anticipate this circumstance and
design grade beams to resist flood, wave, and debris loads and to remain in place and functional when
undermined by scour and erosion (see Figure 17). Grade beams must also be designed and constructed
so the vertical thickness is minimized, thereby reducing the lateral flood,wave, and debris loads acting on
the beam and minimizing the transfer of these loads to the foundation.
Figure 17:
Grade beams that were exposed -
to flood forces during hurricane- i
induced scour; grade beams must y a
resist flood,wave,and debris f
loads when undermined
n
r
6.8 Shear Walls
The NFIP regulations in 44 CFR § 60.3(e) state that only pile
and column foundations are permitted in Zone V. In practice, SHEAR WALLS
this requirement has been relaxed by the NFIP and building ASCE 24 contains flood-related
codes for mid- and high-rise structures to allow certain types requirements and limitations
of solid walls, called shear walls, if detailed engineering for shear walls used to support
calculations demonstrate that such walls are required to buildings in Zone V. Contact your
transfer lateral loads acting on upper stories to the ground, local building department for rules
particularly in extreme-wind zones (see Figure 18). Even in and building code requirements
these cases, shear walls should be used only if foundations and for shear walls in Zone V.
buildings are designed to resist all base flood conditions, all
other design loads, and all appropriate load combinations.
Shear walls should be constructed parallel to the anticipated direction of flood flow and wave attack
(typically perpendicular to the shoreline) to allow floodwater and waves to pass freely. In some cases,
building designs require both shore-perpendicular and shore-parallel shear walls. Use of shore-parallel
shear wall segments should be limited to the minimum length required to transfer upper-story loads to
30 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Figure 18:
High-rise buildings elevated on
shore-perpendicular shear walls
00 t�
-400
40
4001, On
11R
;? x
s i
F M
u
40M
.� i�PMlV.
the foundation. Shore-parallel shear walls should be designed with openings in the walls or gaps between
shear wall segments to minimize trapping of floodwater, waves, and debris and minimize the total flood
loads acting on the building. In any case, designs of these walls must be certified by registered design
professionals as part of the requirement for certification of foundation designs.
Low-rise buildings in Zone V should be designed with pile or column foundations that are consistent
with the NFIP regulations. Post-flood assessments have found that shear walls supporting older low-rise
buildings often do not survive severe storm events. See Figure 19,which shows the failure of a wall section
of a building supported on columns and shore-perpendicular walls. Wall failure led to failure of the
elevated floor beam and floor. In this instance, the building was an older non-conforming building, and
the solid walls rested on shallow footings (a means of support not permitted by the NFIP or building
codes for buildings in Zone V). The wall failure was likely due to both lateral flood loads and foundation
undermining.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 31
Figure 19: 4
Failure of a shore-perpendicular
solid foundation wall that
supported a low-rise building, �-
which resulted in failure of the
beam and floor system that IEL
were supported by the shore-
perpendicular wallILT
rr-
sr
41
0
6.9 Slabs
Concrete slabs are commonly used beneath elevated
buildings in Zone V for vehicle parking and as floors of SLABS AND NFIP FLOOD INSURANCE
enclosed storage or building access areas. The vertical There is no difference in NFIP flood
elements elevating the building should not rest on insurance premiums between having
the slab to avoid an NFIP flood insurance rating of a frangible slab or a self-supporting
"non-elevated." structural slab for two otherwise identical
Post-disaster assessments conducted by FEMA have elevated buildings.
concluded that unreinforced slabs less than 4 inches ------ ------
thick tend to break up into small pieces without causing
adverse effects to elevated buildings (see Figure 20). Reinforced concrete slabs thicker than 4 inches
tend not to break up into small pieces, can become dislodged and act as obstructions, and can transfer
unanticipated loads to building foundations (see Figure 21).
32 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Figure 20:
— Damage to building foundation
Y „ caused in part by failure of the
', reinforced slab undermined by
erosion
4 _
a r
w
Figure 21:
Unreinforced slab that broke apart
without imposing loads on the
foundation
mow
qt.
�µ
�y.
Post-disaster assessments have determined that slabs perform well if they meet the requirement in
ASCE 24-14, Section 9.3, to either:
• Be frangible (break into small pieces), floating slabs supported by compacted soil, not attached to
the building foundation, and designed and constructed with a maximum thickness (traditionally
4 inches),without reinforcement and without turned down edges, or
• Be designed and constructed as self-supporting structural slabs capable of remaining intact and
functional during flooding up to and including base flood conditions, including expected erosion.
Building foundations must be capable of resisting any added loads and increase in local scour due to the
presence of the slabs.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 33
In most circumstances, and for low-rise buildings in Zone V (including residences), the best alternative
is to use frangible slabs. This alternative is also appropriate for other uses of slabs, such as pool decks,
sidewalks, and patios. Figure 22 illustrates one possible design for such a slab.
Contraction joint
Pile/column (typical) (typical—see detail)
Utility riser
Isolation
joint at
pile/column
Plan View
Detail:Section Through Slab
Tooled Contraction Joint Tooled joint
4"max.
Crack resulting from
concrete curing process
Sawcut joint
Sawcut Contraction Joint
4"max.
44*
Crack resulting from
concrete curing process
NOTE: Install expansion and isolation joints as appropriate in accordance
with standard practice or as required by state and local codes.
Figure 22: Example of frangible slab design
34 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Reinforced, self-supporting structural slabs below the BFE may be appropriate for large mid- and high-
rise structures that are supported on deep piles because these structures are typically much heavier and
less prone to damage from flood loads. If a frangible parking slab is constructed beneath such a structure,
reoccupation of an otherwise intact and usable structure after a severe coastal storm event may be delayed
due to loss of parking.A self-supporting structural slab could be considered in such situations.
Reinforced, self-supporting structural slabs and grade beams beneath large buildings should be designed
to be only as thick as necessary to support vehicle loads and other design loads. The slabs and beams
should be connected and integral to the foundations, and all below-BFE components should be designed
to act together to resist flood loads and other design loads. Obstructive effects will be minimized as long
as the slab systems remain intact and horizontal so floodwater and waves pass above and below the slabs.
7 Site Development:
Practices and Issues
This section discusses common site development practices and issues that may significantly affect the
free passage of flood flow and waves under or around elevated buildings. When these practices are
undertaken in accordance with the guidance in this section, they will be deemed to satisfy the NFIP free-
of-obstruction requirement,and the potential obstructive effects will be minimized.
7.1 Accessory Storage Structures
In Zone V, certain small accessories structures (as defined
in a community's floodplain management ordinance, ADDITIONAL ACCESSORY
which has been approved by FEMA) may be permitted STRUCTURE CONSIDERATIONS
below the BFE. Small accessory structures include small Some communities have FEMA-
storage structures such as metal,plastic,or wood sheds that approved regulations that specify
are disposable. FEMA considers "small" to mean less than limitations on the size of accessory
or equal to 100 square feet. structures that are allowed in
SFHAs without having to comply
If accessory storage structures below the BFE do not with elevation requirements. Other
meet the size considerations mentioned above, or if the considerations for accessory
structures are of significant size and made of material that structures are set forth in FEMA
is likely to create either damaging debris or flow and wave- policies and guidance.
diversion problems, communities could consider granting
variances in accordance with their floodplain management Local officials should consult NFIP
ordinances and 44 CFR§ 60.6.Alternatively,a best practice State Coordinators or FEMA Regional
is to have accessory storage structures constructed and Offices for additional guidance and for
appropriate size limits and language to
elevated in compliance with NFIP requirements. include in local regulations.
--------------------------------------------------------------
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 35
Small accessory storage structures that are not elevated must be anchored to resist wind loads (see
Figure 23) and designed to resist flotation that may occur even under relatively shallow flood depths.
However,because small accessory storage structures are unlikely to withstand wave loads, their loss should
be anticipated during the base flood, and the effects that resultant debris may have on nearby structures
must be considered.
Figure 23:
Small accessory structure that was
moved by flood and wind forces ,
tt4
In addition, small accessory storage structures must be unfinished on the interior, constructed of flood
damage-resistant materials, and used only for storage; moreover, if a structure is provided with electricity,
the service must be above the BFE with all branch circuits descending below the BFE fed from ground-
fault circuit interrupter breakers.Accessory storage structures must not be used for any habitable or other
prohibited purpose.
Separate accessory storage structures must not be located directly under elevated buildings.An alternative
is to create storage space below the elevated structure by enclosing an area with breakaway walls.
7.2 Detached Garages
Detached garages, such as those typically built for single-
family homes or multi-family structures, are too large to ALTERNATIVE
qualify as accessory structures that are allowed below the BFE TO DETACHED GARAGES
(see Section 7.1). Therefore, detached garages must be elevated Garages may be constructed
on piles or columns and comply with other requirements for under elevated buildings and
structures in Zone V. enclosed with breakaway walls
e Lar full engineered,free-standing parking garages that satisf (see Technical Bulletin 9, Design
g ' y en g g p g g g y and Construction Guidance for
Zone V design and construction requirements are permitted, Breakaway Walls).
even if portions lie below the BFE (e.g.,vehicle ramps, stairwells,
elevator shafts, parking spaces). These structures are not walled
and roofed in the traditional sense and can be designed to allow
the free passage of floodwater and waves.
36 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
7.3 Erosion Control Structures
Erosion control structures, such as bulkheads,
seawalls, retaining walls, and revetments, are EFFECT OF EROSION CONTROL
obstructions when installed beneath elevated coastal STRUCTURES ON WAVES
buildings and are not permitted even if not attached to Guidance for evaluating potential effects
the building foundations. Erosion control structures of erosion control structures on waves
can transfer damaging flood loads to building is contained in the U.S. Army Corps of
foundations and greatly increase the potential for Engineers Coastal Engineering Manual
redirecting flood flow and waves onto the elevated (2002 and updates). Generally, erosion
portions of coastal buildings). Figure 24 shows an control structures with a steep face (1:2
example of waves running up and overtopping an [vertical to horizontal] or steeper) result in
erosion control structure. Figure 25 shows an example the greatest wave runup.
of timbers attached to a pile foundation (constituting
a bulkhead),which is not permitted.
Figure 24:
Wave runup and overtopping
at an erosion control
structure
W
a
` NwiM
Although the NFIP does not prohibit bulkheads, seawalls, retaining walls, or revetments outside a
building's footprint, communities and design professionals must carefully consider the potentially
significant effects of these structures. A general rule of thumb is the greater the horizontal distance
between an erosion control structure and a building, the less likely that wave runup and overtopping
will adversely affect the building. Although local or state regulations may prohibit the construction of
erosion control structures until erosion is within a few feet of a building foundation (to maximize the
recreational beach area seaward of the structure), the proximity of erosion control structures to buildings
may contribute to wave runup and wave reflection damage.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 37
Figure 25:
Shore-parallel timbers attached
to a pile foundation that were
intended to act as a bulkhead but
constituted an obstruction and are
not permitted
� a
r
tir
FEMAs coastal mapping guidance suggests that a 30-foot-wide "VE overtopping splash zone" (the
area where waves breaking on or running up the seaward face of an erosion control structure land or
splash down) be mapped landward of erosion control structures, but the guidance also contains site-
specific calculations that can lead to a narrower splash zone. For floodplain management purposes, a
30-foot minimum splash zone width is desirable for new construction landward of existing erosion
control structures, but this width may not be feasible for existing buildings situated close to erosion
control structures. There is no established minimum distance between a building and an erosion control
structure, but a reasonable minimum width is 10 to 15 feet. States and communities should take local
conditions and observed building damage into account when establishing minimum distances.
7.4 Fences and Privacy Walls
Fences and privacy walls, including walls separating one property from another, may obstruct or divert
flood flow and waves toward buildings. Their potential effects on buildings, including debris generation,
should be evaluated. Open fences (e.g., wood, plastic, open masonry units, metal slat fencing with
generous openings) are presumed to not cause harmful diversion of floodwater or wave runup and
reflection. Fences with small openings and solid fences and walls may divert flow and waves and can trap
debris.
Solid fences, privacy walls, and fences prone to trapping debris must be designed and constructed to fail
under base flood conditions without causing harm to nearby buildings. Where building or fire codes
require ground-level walls for tenant fire separation, designers should strive to satisfy code requirements
while minimizing potential adverse effects from flood diversion.
38 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Siting of new buildings near fences and privacy walls should be reviewed carefully given the impact that
these structures could have on a building if they fail during a flood event. Figure 26 shows an example
of a shore-perpendicular solid privacy wall that failed during a coastal flood event and damaged the pile
foundation of an adjacent elevated building.
Figure 26:
Shore-perpendicular
reinforced masonry
Pile cap/beam failure privacy wall that
collapsed into the
foundation of an
adjacent building
and contributed to
-- failure of the corner
-' foundation piling and
pile cap/beam
-
Wall collapse
7.5 Fill
NFIP regulations prohibit the use of fill for
structural support of buildings in Zone V. Minor MINOR GRADING AND MINOR QUANTITIES
grading and the placement of minor quantities OF NONSTRUCTURAL FILL
of nonstructural fill are allowed in Zone V Minor grading: Minimum grading necessary to
but only for landscaping, drainage under and provide for landscaping and drainage purposes
around buildings, and support of parking slabs, required or allowed by community regulations,
pool decks, patios, walkways, and similar site subject to the limitations described in this
elements. Nonstructural fill should not prevent Technical Bulletin.
the free passage of floodwater and waves beneath Minor quantity of fill: Minimum quantity
elevated buildings, divert floodwater or waves necessary to provide for adequate drainage
such that building damage is exacerbated, or of areas below and around elevated buildings;
lead to damaging flood and wave conditions on a support of parking slabs, in-ground pool
site or adjacent sites. Nonstructural fill should be decks, decks, patios, walkways, and similar
assumed to wash away and should not be used in site elements; and for site landscaping, subject
foundation design calculations. to the limitations described in this Technical
Determining whether the placement and Bulletin.
shaping of nonstructural fill will be detrimental
is complicated. Therefore, some state and local
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 39
regulations essentially prohibit placement of any nonstructural fill in Zone V. However, such limits on
nonstructural fill can also lead to problems such as ponding of rainfall around or under buildings. Other
states and communities accept some (unspecified) amount of nonstructural fill provided an engineering
analysis is performed and an engineer certifies that the fill will not lead to damaging flow diversion or
wave runup and reflection. However, credible and defensible analyses are difficult to perform using
current engineering methods and models for the small quantities of fill typically used on individual lots.
The placement of nonstructural fill in Zone V for landscaping, drainage, and slab support may be
acceptable under certain circumstances using the evaluation criteria described below. Unless in conflict
with state or local limitations, local officials are expected to apply these criteria using discretion to
achieve the desired performance while giving deference to the general intent of the following criteria as
described in the paragraphs that follow. Several criteria are listed, and they may not all agree, depending
on specific circumstances.
7.5.1 Type of Fill
Fill placed on Zone V sites should be similar to natural soils in the area. In many coastal areas,natural soils
are clean sand or sandy soils free of large quantities of clay, silt, and organic material. Nonstructural fill
should not contain large rocks and debris. If the fill is similar to and compatible with natural soils, there is
no need to require designers to investigate or certify whether the fill has a tendency for excessive natural
compaction; an investigation or certification is a common requirement in many floodplain regulations.
If the fill material is similar to natural soils, its behavior under flood conditions will be similar to the
behavior of natural soils.
7.5.2 Fill Thickness
The addition of small thicknesses of site-compatible, nonstructural fill in Zone V is not likely to lead
to adverse effects on buildings. There are no established rules as to what constitutes an acceptable fill
thickness, so it must be addressed on a case-by-case basis and in some cases may require an engineering
analysis of flow and wave effects of the fill. Designers should check with the community about fill thickness
thresholds triggering engineering analyses.
Placement of up to 2 feet of fill under or around an elevated building can generally be assumed to comply
with free-of-obstruction requirements and be acceptable without engineering analysis or certification,
provided basic site drainage principles are not violated (see Section 7.5.4) and provided there are no
other site-specific conditions or characteristics that would render the placement of the fill damaging to
nearby buildings (e.g., if local officials have observed that the placement of similar quantities of fill has
led to building damage during coastal storm events).
If fill is proposed for a site, the proposed final grade should be compared to local topography. If the
proposed final fill configuration is below the threshold established by the community and the fill
configuration is similar to grades and slopes in the immediate vicinity, a detailed analysis of the effects
on flood flow and waves may not be needed. However, if the proposed fill configuration exceeds the
community's configuration deemed to comply fill thickness threshold or the proposed fill configuration
exceeds local grade heights and variations, an engineering analysis may be required by the community.
In cases where site development involves removing a layer of soil and fill is added to the site later, the fill
thickness should be evaluated relative to the pre-removal soil elevation, not the removed soil elevation.
40 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
7.5.3 Prevention of Ponding
Most communities establish minimum floor elevations to ensure that water does not collect at or under
buildings. Floor elevation requirements are frequently tied to nearby road elevations, and the quantity of
fill required to raise building footprint areas typically falls within the fill height allowance mentioned in
Section 7.5.2. There is no compelling reason to restrict the placement of site-compatible, nonstructural
fill beneath buildings in Zone V if the fill will prevent ponding and saturated soil conditions, as long as
other drainage requirements for grades and slopes can be satisfied.
7.5.4 Site Drainage Requirements
Most communities establish minimum slopes for building sites to facilitate drainage away from buildings
(typically 1 unit vertical to 20 units horizontal [5 percent]). Slopes of 1 unit vertical to 3 units horizontal
(or steeper) can produce appreciable wave runup. Conversely, slopes shallower than 1 unit vertical
to 5 units horizontal (regardless of fill height) will probably not cause or worsen wave runup or wave
reflection capable of damaging adjacent buildings. Figure 27 shows an example of fill placement that is
considered acceptable because the fill depth is modest and the side slopes are gentle. FEMAs Hurricane
Ivan Mitigation Assessment Team concluded that the presence and configuration of the fill did not cause
additional flood or wave damage to either the elevated building or the nearby older non-elevated building
(FEMA, 2005). The adjacent older, non-elevated building in Figure 27 would likely sustain structural
damage during a coastal flood, even if the fill were not present. Swales and conventional site drainage
practices should be used to mitigate potential effects of runoff from filled areas.
Figure 27:
Post-hurricane photo
- ------- showing an elevated building
surrounded by gently
sloping fill and an adjacent,
damaged, older, non-elevated
building
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 41
7.5.5 Vertical Clearance between Top of Fill and Bottom of Lowest Horizontal
Structural Member of Lowest Floor
There are no established rules as to what constitutes acceptable vertical clearance,so it must be addressed
on a case-by-case basis. Designers should check with the jurisdiction about minimum vertical clearance
requirements.
When the BFE is above the existing ground, placement of nonstructural fill between the ground and the
lowest horizontal structural member of the lowest floor may be permitted, but it is advisable to maintain
some vertical clearance between the bottom of the lowest horizontal structural member and the top of the
fill. Vertical clearance should be established to ensure that base flood flow and waves will pass beneath
the elevated building and the fill will not contribute to wave runup and flood damage to the elevated
building.
When the BFE is below the existing ground elevation (see Section 7.6), vertical clearance between the
ground (including any nonstructural fill) and the lowest horizontal structural member of the lowest floor
may not be needed as long as adequate site drainage is provided.
7.5.6 Fill Compaction
The NFIP regulations are explicit in that fill must not be used for structural support of buildings in
Zone V. However, compaction of fill below and around elevated buildings used to support parking slabs,
in-ground pool decks, patios, sidewalks, and similar site amenities is consistent with the intent of the
regulations.
7.5.7 Dune Construction, Repair, and Reconstruction
Dunes are natural features in many coastal areas, and
they can erode during storms and recover naturally over DUNE EXCAVATION MAY INCREASE
time. The natural recovery process can be accelerated POTENTIAL FLOOD DAMAGE
by replacing the eroded dune with compatible sand, Communities must prohibit manmade
planting dune grasses, and installing sand fences (see alteration of sand dunes in Zone V if
Chapter 5 of The Dune Book [Rogers and Nash, 2003]). such alteration would increase potential
In general, these activities should not be considered flood damage(per 44 CFR§60.3(e)(7)).
detrimental even if part of the dune lies under a Where the ground (dune) elevation is at
building's footprint. The addition of sand to restore a or above the BFE, excavation to place the
site to its pre-storm grades and stabilization with dune bottom of the lowest horizontal structural
vegetation will likely do more good than harm in terms member of lowest floor at the BFE is not
of flood damage reduction. recommended and may in fact violate
the limitation on alterations that increase
Concerns about placement of nonstructural, clean potential flood damage.
sand under and around beachfront buildings should
not be the basis for prohibiting dune maintenance and
construction, beach nourishment, or similar activities. Dune construction, repair, and reconstruction
under or around elevated buildings may be assumed to be acceptable as long as the scale and location
of the dune work is consistent with local beach-dune morphology and reasonable vertical clearance is
maintained between the top of the dune and the elevated building's floor system. ASCE 24-14 permits
42 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
dune construction and reconstruction under and around elevated buildings but requires an engineering
report documenting that the fill placement will not cause building damage by wave runup or reflection or
deflection of floodwater.
7.5.8 Timing of Fill Placement
Sometimes fill is placed on a site months or years before building construction begins. This can be
problematic unless the community tracks site improvements and fill placement. If the original natural
grade elevation is unknown, borings or other site investigations may be required to determine the depth
of fill and ensure adequate foundation depth.
7.6 Ground Elevations At or Above the Base Flood Elevation
In some Zone V areas, ground elevations are at or above the BFE, particularly along shorelines with well-
developed dune fields. Mapped Zone V areas with ground above the BFE seem counterintuitive, but they
are possible because of two Zone V mapping considerations:
• Dune erosion. Dunes can erode during the base flood (or lesser floods), resulting in a substantial
lowering of the pre-storm grade to a level below the BFE. The BFE is mapped based on surge and
waves passing over the eroded and inundated ground surface.
• Presence of a primary frontal dune (PFD). Zone V is mapped at a minimum to the inland extent
(heel) of the PFD, even where the dune elevation is higher than the BFE (FEMA, 2014).
A ground elevation at or above the BFE may complicate the need to comply with Zone V design and
construction requirements but does not eliminate it. It does raise the question of how the free-of-
obstruction requirement applies in this situation: Because the soil at the site may erode during a
coastal flood event, the area under the building will be exposed, and the exposed area must be free of
obstructions.
The same free-of-obstruction considerations that apply to buildings elevated above grade apply to
buildings where the BFE is below grade. Buildings must still be designed and constructed on pile or
column foundations that are embedded deep into the ground, and the bottoms of the lowest horizontal
structural members supporting the lowest floor must still be at or above the BFE. Vertical clearance
between the bottom of the lowest horizontal structural member and the ground (see Section 7.5.5) is
not required by the NFIP where ground elevations are at or above the BFE;however, communities should
be contacted because they may have vertical clearance requirements. Any lowest horizontal structural
members that come in contact with the fill must be composed of materials that can resist ground contact
moisture levels. Minor site grading to drain water away from the foundation will also be necessary.
7.7 On-Site Septic Systems
On-site buried septic systems and mounded septic systems in Zone V are frequently exposed and/or
displaced. In addition to compromising their subsequent use, damage can cause release of contents.
Septic systems are often destroyed if they are near a shoreline. Therefore,septic systems should be located
outside areas subject to erosion during the base flood or, if placed in an area subject to erosion, installed
below the depth of expected erosion. The latter stipulation may conflict with septic system groundwater
considerations,in which case an on-site septic system is not appropriate for the area,and alternate designs
may be necessary.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 43
On-site septic system tanks serving elevated buildings must not be structurally attached to building
foundations. Plumbing and piping connections are required, and these items are allowed in Zone V.
However, plumbing and piping components must not be attached to or pass through breakaway wall
panels.
If mounded septic systems are used, they can require significant volumes of fill, which, if placed under
or immediately adjacent to buildings, may constitute obstructions that divert flood flow and waves. An
analysis of flow and wave effects should be undertaken. Mounded septic systems may be allowed in Zone
V if they will not worsen flood and wave conditions for the buildings they serve or nearby buildings (see
Section 7.5.2 for guidance on evaluating mounded systems near elevated buildings).
An additional consideration for on-site septic systems in Zone V is stated in 44 CFR § 60.3(a)(6)(ii) of
the NFIP regulations,which requires "on-site waste disposal systems to be located to avoid impairment to
them or contamination from them during flooding." FEMA P-348 provides additional guidance.
7.8 Restroom Buildings and Comfort Stations
Restroom buildings and comfort stations must be treated the same as other types of structures in Zone
V and must meet the same elevation and design requirements as other buildings, even when the facilities
are situated in public parks or recreation areas.
7.9 Swimming Pools and Spas
Three primary considerations relate to the placement of
swimming pools and spas under or adjacent to buildings in SWIMMING POOLS AND SPAS
Zone V: Pools and spas adjacent to coastal
• Whether the pool or spa will cause increased flood buildings are allowed only if they will
loads on buildings or exacerbate scour and erosion near not act as obstructions that could
buildings. lead to damage to nearby buildings.
This effectively means that most
• Whether the pool or spa configuration is subject to pools and spas must be installed
NFIP use limitations for enclosed areas under elevated in-ground (either frangible or
buildings. immovable) or completely elevated
above the BFE. Swimming pools,
• Whether a removable enclosure is placed around a pool spas, and related equipment are not
or spa (usually in the winter) that will cause increased covered NFIP flood insurance.
flood loads on buildings or exacerbate scour and erosion
near buildings. NFIP flood insurance treats these
enclosures as permanent enclosures even if they are only
used seasonally or for short periods of time.
Pools,pool decks,and walkways that are placed under or adjacent to coastal buildings must be structurally
independent of the buildings and their foundations and must not contribute to building or foundation
damage during the base flood. Three options, also recognized by ASCE 24-14, Section 9.6.2, satisfy this
requirement:
• The pool can be elevated so the bottom of the lowest horizontal structural member supporting the
pool (and the pool itself) is at or above the required flood elevation, or
44 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
• The pool can be designed and constructed to break away without producing debris capable of
damaging nearby buildings, or
• The pool can be designed and constructed to remain in the ground and not divert flow or waves that
can damage nearby buildings.
Registered design professionals must certify that pools or spas beneath or near buildings in Zone V will
not be subject to flotation or displacement that will damage building foundations during a base flood or
lesser event. In cases where pools are empty part of the year, flotation calculations should assume that
pools are empty. Figure 28 shows a spa that was displaced and likely caused the failure of two piles that
supported an elevated deck.
Figure 28:
Failure of two piles supporting an
elevated deck that was likely caused
by movement of a spa
n
�jYI u
iI119
r.
4
i p
`r"I
The NFIP permits swimming pools and spas beneath elevated building only if the top of the pool or spa
and accompanying deck or walkway are flush with the existing grade and the area around the pool or spa
remains unenclosed. However, some states and communities may prohibit or restrict unenclosed pools
and spas beneath elevated buildings. Designers should check with the local jurisdiction for any additional
requirements.
The NFIP limits the use of enclosures under elevated buildings to parking of vehicles, building access,
and storage. Because pools and spas do not satisfy these limitations, they are not allowed to be enclosed,
even if enclosed by glass or breakaway walls. Use of lattice and insect screening is permitted around pools
and spas below elevated buildings.
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 45
8 References
This section lists the references cited in this Technical Bulletin. Additional resources related to NFIP
requirements are provided in Technical Bulletin 0.
ASCE (American Society of Civil Engineers). 2005.ASCE 24-05,Flood Resistant Design and Construction.
Available at https://www.asce.org/.
ASCE. 2014.ASCE/SEI 24-14,Flood Resistant Design and Construction.Available at https://www.asce.org/.
FEMA (Federal Emergency Management Agency). 2005. Mitigation Assessment Team Report:
Hurricane Ivan in Alabama and Florida.Available at https://www.fema.gov/media-library-
data/20130726-1458-20490-9088/fema_489__hurricane_ivan_bpat_.pdE
FEMA. 2009. Local Officials Guide for Coastal Construction. FEMA P-762.Available at https://www.fema.
gov/media-library/assets/documents/16036.
FEMA. 2010a. Home Builder's Guide to Coastal Construction: Technical Fact Sheet Series. FEMA P 499.Available
at https://www.fema.gov/media-library/assets/documents/6131.
FEMA. 2010b. Substantial Improvement/Substantial Damage Desk Reference. FEMA P 758.Available at https://
www.fema.gov/media-library/assets/documents/18562.
FEMA. 2011. Coastal Construction Manual:Principles and Practices of Planning, Siting, Designing, Constructing,
and Maintaining Residential Buildings in Coastal Areas (Fourth Edition). FEMA P-55.Available at
https://www.fema.gov/media-librar-y/assets/documents/3293.
FEMA. 2012.Engineering Principles and Practices for Retrofitting Flood Prone Residential Structures. FEMA
P-259.Available at https://www.fema.gov/media-library/assets/documents/3001.
FEMA, 2014. Primary Frontal Dune Fact Sheet.Available at https://www.fema.gov/media-library/assets/
documents/92336.
FEMA. 2017. Protecting Building Utilities from Flood Damage. FEMA P-348.Available at https://www.fema.
gov/media-librar-y/assets/documents/3729-
FEMA. 2018a.Answers to Questions About Substantially Improved/Substantially Damaged Buildings. FEMA 213.
Available at https://www.fema.gov/media-library/assets/documents/169099.
FEMA. 2019. National Flood Insurance Program Flood Insurance Manual.Available at https://www.fema.gov/
media-library-data/1569523501093-8c 1 d47a539c8e2I b3b8f80cf7b 108fae/a_cover_oct2019.pdf.
FEMA.Various. NFIP Technical Bulletins. Current editions available at https://www.fema.gov/nfip-
technical-bulletins
46 NFIP TECHNICAL BULLETIN 5 MARCH 2O20
Technical Bulletin 0, User's Guide to Technical Bulletins
Technical Bulletin 2, Flood Damage-Resistant Materials Requirements for Buildings Located in Special Flood
Hazard Areas
Technical Bulletin 4,Elevator Installation for Buildings Located in Special Flood Hazard Areas
Technical Bulletin 9,Design and Construction Guidance for Breakaway Walls Below Elevated Buildings
Located in Coastal High Hazard Areas
ICC (International Code Council).
ICC. 2012. 2012 International Building Code.Available at https://codes.iccsafe.org/category/I-Codes.
ICC. 2012. 2012 International Residential Code.Available at https://codes.iccsafe.org/category/I-Codes.
ICC. 2014. 2015 International Swimming Pool and Spa Code.Available at https://codes.iccsafe.org/
content/ISPSC2015?site_type=public.
ICC. 2015. 2015 International Building Code.Available at https://codes.iccsafe.org/category/I-Codes.
ICC. 2015. 2015 International Residential Code.Available at https://codes.iccsafe.org/category/I-Codes.
ICC. 2018. 2018 International Residential Code.Available at https://codes.iccsafe.org/category/I-Codes.
ICC. 2018. 2018 International Residential Code.Available at https://codes.iccsafe.org/category/I-Codes.
Rogers, S.M.,Jr. and D. Nash. 2003. The Dune Book. North Carolina Sea Grant Report SG-03-03.
USACE (U.S.Army Corps of Engineers). 2002 and updates. Coastal Engineering Manual.Available at
https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_l110-2-
1100_Part-06.pdPver=2014-03-10-135408-527
NFIP TECHNICAL BULLETIN 5 MARCH 2O20 47