Resolution 440-2021 1
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9 MONROE COUNTY, FLORIDA
10 MONROE COUNTY BOARD OF COUNTY COMMISSIONERS
11 RESOLUTION NO. 440 - 2021
12
13 A RESOLUTION OF THE MONROE COUNTY BOARD OF
14 COUNTY COMMISSIONERS ADOPTING FEMA TECHNICAL
15 BULLETIN 9 "DESIGN AND CONSTRUCTION GUIDANCE FOR
16 BREAKAWAY WALLS" SEPTEMBER 2021 AS REQUIRED
17 PURSUANT TO MONROE COUNTY CODE SECTION 122-2(C)
18
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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 1. Pursuant to Monroe County Code Section 122-2(c), the Board hereby adopts
36 FEMA Technical Bulletin 9 "Design and Construction Guidance for Breakaway Walls" dated
37 September 2021, a copy of which is attached hereto.
38
39 Section 2. The Clerk of the Board is hereby directed to forward one (1) certified copy of
40 this Resolution to the Building Department.
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I PASSED AND APOPTYP by tfic, Pn,,trd of Cminty nf 114miroc Cnunty,
11he-,I lo;�(hj j I I i ki't hc Id on lic 17"" ri I Ni-,vc,
6 Mayor David Rice Yes
7 Mayor pro tem Craig Cates Yes
8 Commissioner Michelle Coldiron Yes
9 Commissioner Eddie Martinez Yes
Commissioner Holly Merrill Raschein Yes
1 .
BOARD OF COUNTY COMMISSIONERS
OF MONROE CnUNT FLORIDA
BY:
....................... --—-----
Mayor Davis. ice
-APT
14,
21 TTES'f: 1,,EVIN MADOK, CLERK
22
24 As Deputy CIerk
Q225 RM:
Kw*PrrS(.V1.1.
ASMIANT COt,NTYATrOUNFY
11102/2021
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Design and Constr
Guidance
Below Elevated uil in Located in Coastal High
Hazard Areas in Accordance with the
National Flood Insurance Program
NFIP Technical Bulletin 9 / September 202I
FEMAO �
�dLIND S6CF
Comments on the Technical Bulletins should be directed to:
Department of Homeland Security/Federal Emergency Management Agency
Federal Insurance and Mitigation Administration (FIMA) Risk Management Directorate
- Building Science Branch
400 C Street SW, Sixth Floor
Washington, DC 20472-3020
NAP Technical Bulletin 9 (2021) replaces NAP Technical Bulletin 9 (2008), Design and Construction
Guidance for Breakaway Walls.
All illustrations in this document were created by FEMA or a FEMA contractor unless otherwise noted.
All photographs in this document were taken by FEMA or a FEMA contractor unless otherwise noted.
Cover photo: Underside of an elevated building in Zone V post-Hurricane Ivan (2004).The breakaway
walls under the building were removed by waves as intended during the hurricane.
NAP Technical Bulletin 9 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 https://www.fema.gov/
emer enc -managers/risk-management/building-science/fag. To order publications, contact the FEMA
Distribution Center:
If you have any additional questions on FEMA Building Call: 1-800-480-2520
Science Publications, contact the helpline at FEMA- (Monday-Friday, 8 a.m.-5 p.m., EST)
buildingsciencehelp@fema.dhs.g_ov or 866-927-2104. Fax: 719-948-9724
You may also sign up for the FEMA Building Science email Email: FEMApubs@gpo.gov
subscription, which is updated with publication releases Additional FEMA documents can be
and FEMA Building Science activities. Subscribe at htt s:// found in the FEMA Media Library at
service.aovdeliverv.com/accounts/USDHSFEMA/subscriber/ https://www.fema.gov/multimedia-library_
new?topic id=USDHSFEMA 193
Please scan this QR code
Visit the Building Science Branch of the Risk to visit the FEMA Building �•
Management Directorate at FEMA's Federal Insurance Science web page.
and Mitigation Administration at https://www.fema.®ov/ 0•
emergency-manag ers/risk-manage ment/b ui ld i ng-sci ence.
Table of Contents
Acronyms..................................................................................................................................................................J*N
1 Introduction........................................................................................................................................................ 1
1.1 Alternatives to Breakaway Walls........................................................................................................................2
1.2 Design Safe Loading Resistance(Ultimate Load).............................................................................................2
1.3 Breakaway Nall Design Methods Provided in This Technical Bulletin...........................................................3
2 NIP Regulations................................................................................................................................................5
BuildingCodes and Standards.......................................................................................................................... 7
3.1 International Residential Code..........................................................................................................................8
3.2 International Building Code and ASCE 24..................................................................................................... 11
3.3 Flood Openings in Breakaway Walls............................................................................................................... 12
4 NFIP Flood Insurance Implications ..................................................................................................................13
Wave Loads on Building Elements ...................................................................................................................14
Breakawayall Performance..........................................................................................................................15
6.1 Observations of Breakaway Nall Performance................................................................................................ 15
6.2 Research on Breakaway Nall Performance..................................................................................................... 19
7 Design Methods for Breakaway Walls............................................................................................................. 22
Prescriptive Design Method for Breakaway Walls...........................................................................................24
8.1 ApplicabilitV.....................................................................................................................................................24
8.2 Design'XIethodology........................................................................................................................................25
8.3 Design Details .................................................................................................................................................32
8.4 Example............................................................................................................................................................36
Simplified Design Method for Breakaway Walls............................................................................................. 36
9.1 ApplicabilitV.....................................................................................................................................................36
9.2 Design'XIethodology........................................................................................................................................37
9.3 Design Details..................................................................................................................................................45
9.4 Example............................................................................................................................................................45
10 Performance-Based Design Method for Breakaway Walls............................................................................ 45
10.1 ApplicabilitV.....................................................................................................................................................45
10.2 Design'XIethodology........................................................................................................................................45
10.3 Segmented Breakaway Walls............................................................................................................................46
10.4 Design Details..................................................................................................................................................47
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 1
11 Breakaway Walls and Other Building Elements..............................................................................................48
11.1 Attendant Utilities and Equipment..................................................................................................................48
11.2 Equipment(Tanks) ...........................................................................................................................................49
11.3 Garage Doors...................................................................................................................................................49
11.4 Partial-Height Breakaway Wall Systems..........................................................................................................49
11.5 Firewalls between Townhomes,Rowhomes, and Multi-family Housing........................................................52
11.6 Soffits under Elevated Buildings with Breakaway Walls..................................................................................52
11.7 Exterior Finishes...............................................................................................................................................53
11.8 Interior Finishes................................................................................................................................................53
12 Construction Materials..................................................................................................................................... 53
12.1 NNood'XIaterials................................................................................................................................................53
12.2 Metal Connectors and Fasteners......................................................................................................................54
12.3 'XIasonry'XIaterials...........................................................................................................................................54
12.4 Other'XIaterials................................................................................................................................................54
13 ExistingBuildings: Repairs, Remodeling, Additions, and Retrofitting........................................................... 55
14 Best Practices in Coastal A Zones................................................................................................................... 55
15 References ........................................................................................................................................................57
.1.1 List of Figures
Figure 1: Breakaway walls enclosing an area below an elevated building in Zone V(left); breakaway wall
enclosures that have broken away as a result of lateral flood loads(right)...................................................... I
Figure 2: Flood openings in breakaway walls ............................................................................................................ 13
Figure 3: Impact of a breaking wave on a vertical surfac.e.......................................................................................... 14
Figure 4: Breakaway walls under an elevated building that were removed by waves(i.e.,performed as
intended) during Hurricane Ivan in 2004(Gulf Shores,AL) ...................................................................... 15
Figure 5: Unreinforced masonry breakaway walls removed by waves
(i.e.,performed as intended) during Hurricane Irma in 2017 (Monroe County,FL) ................................. 16
Figure 6: Damage caused by waves running up the exterior wall prior to dislodging of breakaway walls
during Hurricane Ivan in 2004(Pensacola Beach,FL) .............................................................................. 17
Figure 7: Non-compliant joint detailing,resulting in the propagation of damage above the lowest floor
when the breakaway walls broke away during Hurricane Ike in 2008 (Seabrook,TX) ............................. 17
Figure 8: Utilities attached to breakaway walls that may have prevented the walls from breaking away,
resulting in additional damage to the structure during Hurricane Ike in 2008 (Galveston
Island,TX) .................................................................................................................................................. 18
Figure 9: Cross bracing that interfered with the failure of a breakaway wall ............................................................ 18
Figure 10: Non-compliant breakaway walls that were nailed over the piles and floor beam,preventing a
clean break during Hurricane Ike in 2008 (Gulf Shores,AL) ..................................................................... 19
ii WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
Figure 11: Expected failure rnode of wood-framed breakaway wall based on full-scale testing ..................................20
Figure 12: Secondary failure mode of wood-framed breakaway wall as determined from full-scale testing ..............20
Figure 13: Expected failure mode of unreinforced masonry breakaway wall ..............................................................21
Figure 14: Typical wood-framed breakaway wall construction(prescriptive design method)......................................26
Figure 15: Typical steel stud-framed breakaway wall construction with designated section type,gauge, and
size(prescriptive design method)..................................................................................................................28
Figure 16: Typical breakaway masonry wall where the lowest horizontal structural member is a concrete
beam(prescriptive design method)...............................................................................................................29
Figure 17: Typical breakaway masonry wall where the lowest horizontal structural member is a timber
structural beam with floor joists bearing on the structural beam(prescriptive design method).................30
Figure 18: Typical breakaway masonry wall where the lowest horizontal structural member is a timber
structural beam with floor joists hanging from the face of the structural beam(prescriptive design
method)......................................................................................................................................................... 31
Figure 19: Separation joint between sheathing and wall covering(e.g., stucco, siding) on house walls and
breakaway-'walls ...........................................................................................................................................34
Figure 20: Utility blockout for an unreiuforced masonry breakaway wall ...................................................................35
Figure 21: Typical wood-framed breakaway wall construction(simplified design method) ........................................37
Figure 22: Typical steel stud-framed breakaway wall construction(simplified design method) ..................................41
Figure 23: Example of a segmented breakaway wall using horizontal segments..........................................................47
Figure 24: Prohibited partial-height breakaway wall showing a breakaway portion that extends only up to
the minimum required elevation and permanent walls that extend from the top of the breakaway
wall up to the lowest horizontal structural member supporting the lowest floor.........................................50
Figure 25: Breakaway walls that extend up to the lowest horizontal structural member of the lowest floor,
which are considered full-height breakaway walls.......................................................................................50
Figure 26: Breakaway walls that do not extend up to the lowest horizontal structural member of the lowest
floor,which are allowable if the space between the top of the breakaway wall and the lowest
horizontal structural member is open or covered with open lattice-work or insect screening and
the performance-based design method is used.............................................................................................51
Figure 27: Breakaway walls that do not extend to the bottom of the ground or parking slab,which are
allowable if a registered professional engineer or architect verifies that the breakaway walls will
break away during a base flood event and the performance-based design method is used.........................52
Figure 28: Home elevated above the PFE in Zone AE showing successful failure of breakaway walls........................56
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 in
a1 a1 List of Tables
Table 1: Comparison of Selected 2021 IRC and NFIP Requirements........................................................................8
Table 2: Comparison of Selected 2021 IBC and ASCE 24-14 Requirements with NFIP Requirements................. 11
Table 3: Parameters for Breakaway Wall Design Methods........................................................................................23
Table 4: Required Size and Number of Galvanized Common Nails for Wood-Framed Breakaway Walls
with Different Heights and Pile Spacings.....................................................................................................27
Table 5: Required Number of 1-inch-long No. 6 Self-Tapping Screws for Steel Stud-Framed Breakaway
Walls with Different Heights and Pile Spacings...........................................................................................28
Table 6: Required Number of Galvanized 16d Common Nails for Restraining 2x4s on Unreinforced
Masonry Breakaway Walls with Different Pile Spacings.............................................................................32
Table 7: Required 2x4(No. 2 Grade) Stud Spacing for Wood-Framed Breakaway Walls of Different
Heightsand Design Wind Speeds................................................................................................................38
Table 8: Required Number of 10d Galvanized Common Nails for NVood-Framed Breakaway Walls with
Different Wall Heights and Design Wind Speeds........................................................................................39
Table 9: Required 362S162-33 Stud Spacing for Steel Stud-Framed Breakaway Walls with Different
Heightsand Design Wind Speeds................................................................................................................42
Table 10: Required Number of 1-inch long No. 6 Self'-Tapping Screws for Steel-Stud Framed Breakaway
Walls with Different Heights and Design Wind Speeds...............................................................................43
Acronyms
APA The Engineered Wood Association I C C International Code Council
(formerly American Plywood I-Codes° International Codes
°
Association)
IRGJ�; International Residential Godej�;
ASCE American Society of Civil Engineers
LiMWA Limit of Moderate Nave Action
ASTM ASTM International(formerly
-IAT 'Xlitigation Assessment Team
American Society for Testing and
Materials) NFIP National Flood Insurance Program
AWC American Wood Council O.C. on center
BFE base flood elevation psf, pounds per square foot
CFR Code of Federal Regulations psi pounds per square inch
CMU concrete masonry unit SAE SAE International(formerly Society
of Automotive Engineers)
FEMA Federal Emergency Management
Agency SEI Structural Engineering Institute
FIRM Flood Insurance Rate Map SFHA Special Flood Hazard Area
IBCv International Building Codev
iv WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
1 Introduction
This Technical Bulletin provides guidance on the National Flood Insurance Prograrn (NFIP) requirements
for the design and construction of breakaway walls that are used to create enclosures below the lowest floor
of elevated structures in Coastal High Hazard Areas. A breakaway wall is a wall that is not part of the structural
support of a building and is intended through its design and construction to collapse under specificc lateral
loading forces without causing damage to the elevated portion of the building or supporting foundation system
(see Figure 1). Coastal High Hazard Areas are designated as Zone V (V, VE, V1-30, and VO) on a community's
Flood Insurance Rate'lap (FIR'I).
Figure 1: Breakaway walls enclosing an area below an elevated building in Zone V(left); breakaway wall enclosures that
have broken away as a result of lateral flood loads(right)
This Technical Bulletin presents three methods of
designing breakaway walls that are consistent with the NFIP TECHNICAL BULLETIN 0
NFIP regulations: NFIP Technical Bulletin 0, User's Guide to
• Prescriptive design method Technical Bulletins, should be used as a
reference with this Technical Bulletin.Technical
• Simplified design method Bulletin 0 describes the purpose and use of the
• Performance-based design method Technical Bulletins. It includes common concepts
and terms, lists useful resources, and includes a
Breakaway walls that are designed using the simplified crosswalk of the sections of the NFIP regulations
and performance-based design methods must be certified identifying the Technical Bulletin that addresses
by a registered professional engineer or architect as each section of the regulations and a subject
meeting the NFIP requirements. Breakaway walls index.
designed using the prescriptive design method do not
require certification by a registered professional engineer Readers are Cautioned that the definitions of
or architect, although state or local governments may some of the terms that are used in the Technical
require certification. Regardless of which method is used, Bulletins are not the same when used by the NFIP
for the purpose of rating flood insurance policies.
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 1
breakaway walls rnust be designed and constructed to rneet the applicable building codes and standards adopted by
states and communities.
The three design methods are described further in Sections 1.2, 8, 9, and 10 of this Technical Bulletin.
1.1 Alternatives to Breakawayails
The NFIP regulations permit areas below elevated buildings in Zone V to be enclosed in one of three ways: open
lattice-work,insect screening, and non-supporting breakaway walls(44 GFR§60.3(e)(5)).
Open lattice-work and insect screening are not considered walls or obstructions. These materials are assumed
to collapse under wind and base flood loads without causing the elevated portion of the building or supporting
foundation system to collapse, be displaced, or sustain other structural damage. To increase the likelihood that these
materials will collapse as intended, the vertical framing members (such as 2x4s) on which the open lattice-work or
insect screening is mounted should be spaced at least 2 feet apart. Metal and synthetic mesh insect screening are both
acceptable.
Although the NFIP regulations explicitly identify wood lattice, the Federal Emergency Management Agency(FEMA)
considers plasticc lattice acceptable provided the material that is used to fabricate the lattice is no thicker than 1/2
inch and the finished sheet has at least 40 percent of its area open (see NFIP Technical Bulletin 5, Free-of Obstruction
Requirements).Wood and plasticc lattices are usually available in 4-foot by 8-foot sheets.
Although not specified in the NFIP regulations, areas below elevated buildings may also be surrounded by plastic. or
wood shutters, slats, or louvers(see Technical Bulletin 5). These materials must:
• Be cosmeticc only and not provide structural support to the building
• Have at least 40 percent of the area open
• Be no thicker than 1 inch
1.2 Design SafeLoading i t (Ultimate Load)
Previous editions of this Technical Bulletin refer to breakaway walls as having a design safe loading resistance
(referred to in ASGE 7 as allowable load) of 20 psf or less. To make the calculation of wind loads consistent with
the approach used for seismicc design, the standard approach to wind design introduced in ASGE 7-10, Minimum
Design Loads for Buildings and Other Structures, uses a design methodology applying ultimate loads. Therefore, this
Technical Bulletin uses the conversion of the allowable load of not less than 10 psf and no more than 20 psf into the
ultimate load of not less than 17 psf and no more than 33 psf for the prescriptive design method. This approach is
consistent with the wind design procedures in ASGE 7-10. Although there have been changes to design methods for
breakaway walls, the revised values that express the design safe loading resistance as ultimate loads are equivalent to
the allowable loads provided in the NFIP requirements for breakaway walls.
Although there have been changes to design methods for breakaway walls, the revised values that express the design
safe loading resistance as ultimate loads are equivalent to the allowable loads provided in the NFIP requirements for
breakaway walls.
2 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
1.3 Breakaway Wall Design Methods Provided in This Technical Bulletin
The designer may select one of three design methods for breakaway walls: prescriptive, simplified, or performance-
based. The methods are consistent with the NFIP regulations.
1.3.1 Prescriptive Design Method
The NFIP design requirements for breakaway walls were the subject of research performed for FEMA and the
National Science Foundation by North Carolina State University and Oregon State University (Tung et al., 1999).
The research evaluated failure mechanisms in full-scale, laboratory wave-tank tests of breakaway wall panels. The
results influenced the prescriptive design method that is described in this Technical Bulletin.
The prescriptive design method for the design and construction of a compliant breakaway wall system that is
within the load parameters provided in Section 7 of this Technical Bulletin uses common materials and detailing
practices, which allow the designer to use the prescriptive details provided in Section 8.3 of this Technical Bulletin.
Although certification is not required by the NFIP for breakaway walls that conform to the specifications in the
prescriptive design method, state or local governments may require certification.
See Section 8 of this Technical Bulletin for more information on the prescriptive design method.
1.3.2 Simplified Design Method
The simplified design method uses the common materials and detailing practices that are similar to those in the
prescriptive design method. The method is simplified because breakaway walls are designed to minimize flood loads
to the elevated structure and foundation system. The method is permitted for walls that are designed to have a design
safe loading resistance (ultimate load) of more than 33 psf but no more than 70 psf for wood-framed and steel stud-
framed breakaway walls and more than 33 psf but no more than 55 psf for unreinforced masonry breakaway walls. A
design certification is required for breakaway walls designed using the simplified design method.
See Section 9 of this Technical Bulletin for more information on the simplified design method.
1.3.3 Performance-Based Method
The performance-based design method allows more detailing freedom for breakaway walls than the other two
methods but requires the designer to consider the combined effect of wind forces acting on the elevated portion of the
structure and wind and flood loads acting on the foundation system and breakaway walls. A design certification is
required for breakaway walls designed using the performance-based design method.
See Section 10 of this Technical Bulletin for more information on the performance-based design method.
Questions about breakaway wall system requirements should be directed to the appropriate local official, NFIP State
Coordinating Office, or FEMA Regional Office.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 3
TERMS USED IN THIS TECHNICAL L TI
Breakaway wall:"A wall that is not part of the structural support of the building and is intended through its
design and construction to collapse under specific lateral loading forces, without causing damage to the
elevated portion of the building or supporting foundation system" (44 CFR§59.1).
Coastal A Zone: "Area within a special flood hazard area, landward of a V Zone or landward of an
open coast without mapped V Zones. In a Coastal A Zone, the principal source of flooding must be
astronomical tides, storm surges, seiches, or tsunamis, not riverine flooding. During the base flood
conditions, the potential for breaking wave heights shall be greater than or equal to 1.5 feet. The
inland limit of the Coastal A Zone is (1) the Limit of Moderate Wave Action if delineated on a FIRM, or
(2)designated by the authority having jurisdiction" (ASCE 24-14, used with permission from ASCE).
Coastal High Hazard Area: "An area of special flood hazard extending from offshore to the inland limit of
a primary frontal dune along an open coast and any other area subject to high velocity wave action from
storms or seismic sources" (44 CFR § 59.1). The coastal high hazard area is shown on the FIRMs or other
flood hazard maps as Zone V, VO, VE, or V1-30.
Enclosed area (enclosure):An area below an elevated building that is enclosed by walls on all sides.
Flood damage-resistant material: Any building product (material, component, or system) capable of
withstanding direct and prolonged contact with floodwaters without sustaining significant damage.
"Prolonged contact" means at least 72 hours, and "significant damage" means any damage requiring more
than cosmetic repair, which includes cleaning, sanitizing, and resurfacing (e.g., sanding, repair of joints,
repainting).
Freeboard: "Factor of safety usually expressed in feet above a flood level for purposes of flood plain
management" (44 CFR§59.1).
Limit of Moderate Wave Action (LiMWA):The LiMWA marks the inland limit of the Coastal A Zone—the
part of the coastal SFHA referenced by building codes and standards where wave heights can be between
1.5 and 3 feet during a base flood event(FEMA,2019). FEMA began delineating the LiMWA on coastal FIRMs
in 2009.
Lowest floor: Lowest floor of the lowest enclosed area of a building, including basement.An unfinished or
flood-resistant enclosure that is used solely for parking of vehicles, building access, or storage in an area
other than a basement area is not considered the lowest floor, provided the enclosure is built in compliance
with applicable requirements.
Special Flood Hazard Area(SFHA):Area subject to flooding by the base flood (1-percent-annual-chance
flood) and shown on FIRMs as Zone A or V.
Zone A: Flood zones shown on FIRMs as Zones A,AE,Al-30,AH, AO,A99, and AR.
Zone V: Flood zones shown on FIRMs as Zones V, VE,V1-30, and VO.
Other terms used in this Technical Bulletin are defined in the glossary in Technical Bulletin 0.
4 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
2 NFIP Regulations
An important NFIP objective is protecting buildings constructed in Special Flood Hazard Areas (SFHAs) frorn
damage caused by flooding. The SFHA is the land area subject to flooding by the base flood. SFHAs are shown
on FIRMS prepared by FEMA as Zones A and V. The base flood is the flood that has a I 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 Improvement,including improvements, alterations, and additions
• Repair of'buildings determined to have incurred Substantial Damage
The NFIP regulations that are applicable in SFHAs
identified as Coastal High Hazard Areas (Zones V, ZONE V CERTIFICATION OF
VE, VI-30, and VO) require the bottom of the lowest STRUCTURAL DESIGN AND
horizontal structural member of the lowest floor to be METHODS OF CONSTRUCTION
elevated to or above the base flood elevation (PFE) The NFIP regulations require communities
on an open foundation system (pilings or columns) to to ensure that design and construction meet
allow waves and water moving at high velocity to flow Zone V requirements, including breakaway wall
beneath buildings. Coastal waves and flooding can requirements. Registered professional engineers
exert strong hydrodynamicc and potential debris impact or architects must develop or review structural
loads on any building element that is exposed to the designs, specifications, and plans for new
waves or flow of'water. Obstructions below an elevated construction and Substantial Improvements and
building can significantly increase the potential for certify that designs and methods of construction
flood damage by increasing the surface area subject to are in accordance with the accepted standards
wave or potential debris impacts and velocity flow. of practice. Registered professional engineers
The NFIP regulations also require that unenclosed and architects should consult with communities
areas below the lowest floor of elevated buildings be on their certification requirements before
free of obstructions and that enclosed areas be enclosed
starting the design. Communities must obtain
by non-supporting breakaway walls, open lattice-work,
and retain the certifications.
or insect screening. The walls, lattice, or screening must Satisfying the NFIP breakaway wall requirements
collapse under wave loads without causing the elevated is part of the certification. The community must
building or supporting foundation system to collapse, ensure that construction is compliant with the
be displaced, or sustain other structural damage. NFIP regulations. Jurisdictions may require
Enclosed areas are allowed to be used only for parking post-construction certification by a registered
ofvehicles,building access, or storage. professional engineer or architect.
All materials used below the PFE, including materials See Technical Fact Sheet 1.5 in FEMA P-499,
used to construct enclosures, must be flood damage- Home Builder's Guide to Coastal Construction
resistant, and enclosures must be constructed using Technical Fact Sheet Series(FEMA, 2010a),for a
methods and practices that minimize the potential for discussion of Zone V certification requirements
flood damage. and a sample form that can be used. If the
sample form is used, Section IV should be
modified to reflect the ultimate load as the
design safe loading resistance.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 5
The terms that are used by the NFIP that are relevant to breakaway walls are defined in Title 44 of the Code of
Federal Regulations (CFR) Section 59.1, Definitions, and the NFIP regulations for breakaway walls are codified in
44 CFR Part 60, Criteria for Land Management and Use.
Section 59.1 defines breakaway walls as follows:
Breakaway wall means a wall that is not part of the structural support of the building and is intended
through its design and construction to collapse under specificc lateral loading forces, without causing
damage to the elevated portion of the building or supporting foundation system.
Section 60.3(e)(4)states that a community shall:
Provide that all new construction and substantial improvements in Zones V1-30 and 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 (1) 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
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)(1) and(ii)of this section.
Section 60.3(e)(5) states that a community shall require:
... that all new construction and substantial improvements within Zones V1-30, 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 latticework, or insect screening intended to collapse under
wind and water loads without causing collapse, displacement, or other structural damage to the elevated
portion of the building or supporting foundation system. For the purposes 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.t 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:
(1) 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.
1 Footnote added for this Technical Bulletin.Because the wind design approach changed in ASCE 7-10,this Technical Bulletin uses 33 psf ultimate
load as the requirement,which is the calculated equivalent of the 20 psf allowable load that is specified in this section of the NFIP regulation(44 CFR
§60.3(e)(5)).
6 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
NFIP REQUIREMENTS AND HIGHERREGULATORY STANDARDS
Federal, State,or Local Requirements. Federal, 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 NAP 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 state or local building codes must also be met.
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 the NFIP requirements for new construction. Some communities modify
the definitions of Substantial Improvement 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 Improved/Substantially Damaged Buildings(2018a).
Higher Building Elevation Requirements.Some states and communities require that buildings be
elevated above the NFIP minimum required elevation.The additional elevation is called freeboard. Design
professionals, builders, and property owners should check with local officials to determine whether a
community has a freeboard requirement. The guidance in this Technical Bulletin is that freeboard should
only be applied when determining the minimum required elevation for the lowest horizontal structural
member of the lowest flood and the height that flood damage-resistant materials are required to extend
to. Loading requirements are only to the BFE in breakaway wall designs.
3 Building Codes and Standards
In addition to cornplying with NFIP requirernents,
all new construction, Substantial Improvements, I-CODES AND COASTAL A ZONE
and repair of Substantial Damage must comply with The 2015 and later editions of the International
applicable building codes and standards that have Codes (I-Codes)treat Coastal A Zones like
been adopted by states and communities. Zone V if a Limit of Moderate Wave Action
The International Codes° (I-Codes°), published by (LiMWA) is delineated on FIRMs.The 2015 and
the International Code Councils (ICC�), are a family later editions of the I-Codes also require flood
of codes that includes the International Residential openings in breakaway walls(see Section 3.3 of
Code° (IR '°), International Building Code° JBC°), this Technical Bulletin).
International Existing wilding Gode� (IEPG�) If a community designates an area as a
and codes that govern the installation of mechanical, Coastal A Zone in its building code or floodplain
plumbing, fuel gas service, and other aspects of management regulations, buildings in that area
building construction. FEMA has deemed that the are required to comply with Zone V requirements,
latest published editions of the I-Codes generally including for breakaway walls.
meet or exceed NFIP requirements for buildings
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 7
and structures. Excerpts of the flood provisions in the I-Codes are available on the FENIA Building Science — Flood
Publications webpage at littps: ««-r-v.fema.gov emergcucy-mauaget Slrisk-mauagemcutlbuildirig-scicuc(,lflood.
.1 International Residential Code
The International Residential Code(IRC) applies to one-and two- INTERNATIONAL SI TI L
family dwellings and townhomes not more than three stories above CODE COMMENTARY
grade plane.
The ICC publishes companion
Depending on location, the design wind speeds may exceed the commentary for the IRC. Although not
prescriptive limits specified in the IRC. The prescriptive design regulatory, the commentary provides
provisions of the 2018 and later editions of the IRC are applicable guidance that is useful in complying
only to locations as defined in IRC Section R301.2.1. Thus, with, interpreting, and enforcing the
one- and two-family dwellings in areas where ultimate design requirements of the code.
wind speeds exceed these minimum values must be designed in
accordance with the wind design requirements of the IBC or other
standard referenced in the IRC (see IRC Section R301.2.1.1).
The primary reference for wind and seismic.loading in the 2018 and 2021 editions of the IBC and IRC is ASCE 7-16,
Minimum Design Loads and Associated Criteria for Buildings and Other Structures.
The IRC requirements related to breakaway walls are summarized in Table 1, with a comparison to NFIP
requirements. Table 1 refers to selected requirements of the 2021 IRC, noting changes from the 2018, 2015, and 2012
editions. Subsequent editions of the IRC should include comparable requirements.
Table 1: Comparison of Selected 2021 IRC and NFIP Requirements
• e� � •® e e e o � l� �'i� I's�''
ee a• c m m es e0 s c cue, ce � � � ®® 1"icelu•e
Equipment Section R322.1.6 Protection of mechanical, plumbing,and Equivalent to NFIP 44 CFR
(electrical, electrical systems. §60.3(a)(3)(iv), with more
plumbing, and Requires new electrical, plumbing, and mechanical system specificity(components are not
mechanical elements and replacement systems that are part of Substantial to be mounted on or penetrate
systems) Improvements to be elevated to or above the elevations required through breakaway walls).
for buildings or, if below these elevations,to be designed
and installed to prevent water from entering or accumulating
within the components and able to withstand certain loads
and stresses. Specifies that systems, fixtures, and equipment
components must not be mounted on or penetrate through
walls intended to break away.
Change from 2018 to 2021 IRC:Applies requirements below the
elevation required in Section R322.3.2 for the lowest horizontal
structural member of the lowest floor.
Change from 2015 to 2018 IRC: No change.
Change from 2012 to 2015 IRC: No change.
3 NFIP TECHNICAL BULLETIN 9 SEPTEMBER 2021
Table 1: Comparison of Selected 2021 IRC and NFIP Requirements(cont.)
®� e• ` m m � m � a cue. `d � � � e®® eu•�
Free of Section R322.3.3 Foundations. Equivalent to NFIP 44 CFR
obstruction Requires that areas below elevated buildings in Coastal §60.3(e)(4)and (5), except that
High Hazard Areas(Zone V)and Coastal A Zones be free of the 2015 and later editions
obstructions or enclosed by breakaway walls. In Coastal A of IRC apply requirements in
Zones, filled stem wall foundations that are designed to resist both Zone V and Coastal A
flood loads, erosion,and scour are allowed as an exception. Zones, with an exception that
Change from 2018 to 2021 IRC: Requirements are in a permits stem wall foundations in
numbered list, and requirements are more clearly applied to Coastal A Zones.
column foundations.
Change from 2015 to 2018 IRC: Subsection numbering is
changed due to the addition of subsections that expand
requirements for concrete slabs(322.3.4); stairways and ramps
(R322.3.7), and decks and porches (R322.3.8).
Change from 2012 to 2015 IRC:Applies Zone V requirements in
Coastal A Zones, if delineated, with an exception that permits
stem wall foundations.
Enclosed areas Section R322.3.5 Walls below required elevation. Exceeds NFIP 44 CFR
(walls) Requires that enclosures below elevated buildings in Coastal §60.3(e)(5)by specifying
High Hazard Areas(Zone V)and Coastal A Zones: that components must not to
1. Be constructed with insect screening or open lattice or be mounted on or penetrate
designed to break away under certain wind and flood loads through breakaway walls and
without damaging the elevated building or the building by requiring flood openings in
foundation breakaway walls(see Section 3.3
of this Technical Bulletin).
2. Do not have electrical, mechanical, and plumbing system
components mounted on or penetrate through breakaway
walls
3. Have flood openings that meet the criteria in Section
R322.2.2, Item 2
Change from 2018 to 2021 IRC:Applies requirements below the
elevation required in Section R322.3.2 to the lowest horizontal
structural member of the lowest floor.
Change from 2015 to 2018 IRC: No change.
Change from 2012 to 2015 IRC: Clarifies that attachment or
penetration by electrical, mechanical, or plumbing systems to
breakaway walls is not permitted.
Enclosed Section R322.3.6 Enclosed areas below required elevation. Equivalent to NFIP 44 CFR
areas(use Requires enclosed areas below the required elevation to be §60.3(e)(5)regarding use of
limitations) used solely for parking of vehicles, building access, or storage. enclosed areas.
Change from 2018 to 2021 IRC:Applies requirements below the
elevation required in Section R322.3.2 for the lowest horizontal
structural member of the lowest floor.
Change from 2015 to 2018 IRC: No change.
Change from 2012 to 2015 IRC: No change.
NFIF TECHNICAL BULLETIN 9 SEPTEMBER 2021 9
Table 1: Comparison of Selected 2021 IRC and NFIP Requirements(cont.)
®� e• ` m m � m � a cue. `d � � � e®® eu•�
Stairways and Section R322.3.7 Stairways and ramps. Exceeds NFIP 44 CFR
ramps Requires areas below stairways and ramps, if enclosed by walls, §60.3(e)(5)by specifying
to be enclosed by breakaway walls. requirements for stairways and
Change from 2018 to 2021 IRC:Applies requirements below the ramps, including breakaway
elevation required in Section R322.3.2 to the lowest horizontal walls when areas under
structural member of the lowest floor. stairways and ramps are
enclosed by walls.
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 44 CFR
porches Requires attached decks and porches to meet the lowest §60.3(e)(5)by specifying
floor elevation requirement and have compliant foundations requirements for decks and
or be cantilevered from or knee-braced to the building. Self- porches.
supporting decks and porches must be designed to remain in
place or break away and may be below the required elevation if
not enclosed by solid walls(including breakaway walls).
Change from 2018 to 2021 IRC:Applies requirements below the
elevation required in Section R322.3.2 to the lowest horizontal
structural member of the lowest floor.
Change from 2015 to 2018 IRC: New section for decks and
porches incorporating language from R322.3.3.
IRC WIND PROVISIONR T CTI THE BUILDING ENVELOPE
ON BUILDINGS IT AKAWALLS
Since the 2015 edition of the IRC, Section R322.3.6.1 (Protection of building envelope), has required
an exterior door at the top of stairs that provide access to the building when the area below the lowest
floor is enclosed by walls that are designed to break away.This provision is to ensure that the building
is protected from the effects of wind when the breakaway walls have failed (i.e., perform as intended).
A similar requirement is provided in ASCE 24-14, Section 4.6 (Enclosed areas below design flood
elevation).
10 NFIP TECHNICAL BULLETIN 9 SEPTEMBER 2021
3.2 International Building Code and ASCE 24
The flood provisions of the latest published editions of the IBC
generally meet or exceed NFIP requirements for buildings largely
through reference to the standard ASCE 24, Flood Resistant Design INTERNATIONAL BUILDING CODE
and Construction. ASCE 24 is developed by the American Society of AND ASCE 24 COMMENTARIES
Civil Engineers(ASCE). The IBC applies to all applicable buildings The ICC publishes companion
and structures. NVhile primarily used for buildings and structures Commentary for the IBC, and ASCE
other than dwellings within the scope of the IRC, the IBC may be publishes companion commentary
used to design dwellings. for ASCE 24. Although not
regulatory, the commentaries provide
The IBC and ASCE 24 requirements related to breakaway information and guidance that are
walls are summarized in Table 2 with a comparison to NFIP useful in complying with, interpreting,
requirements. Table 2 refers to selected requirements of the 2021 and enforcing requirements.
IBC and ASCE 24-14 (noting changes from 2018, 2015, and 2012
IBC and ASCE 24-05). Subsequent editions of the IBC and ASCE
24 should include comparable requirements.
Table 2: Comparison of Selected 2021 IBC and ASCE 24-14 Requirements with NFIP Requirements
Mea •s 0 ° `® (Ylll�I IV 9 9Y" I�yi Vll'i� 4���Y ��YIY�ii ���+� ��1
a a• a 0 1 e 1 e° f c e�,�i, ,a �r� CI EII✓ e uu Y, 1 Y � r,
General 2021 IBC Section 1612.2 Design and construction. Exceeds NFIP 44 CFR§60.3(e)
design Requires design and construction of buildings and structures by referring to ASCE 24, which
requirement located in Coastal High Hazard Areas(Zone V)and Coastal A has more specificity for some
Zones to comply with ASCE 24 and Chapter 5 of ASCE 7. foundation elements and higher
Change from 2015 to 2018 IBC: No change. minimum building elevations and
requires meeting Zone V design
Change from 2015 to 2018 IBC: Sections renumbered. and construction standards in
Change from 2012 to 2015 IBC:Applies Coastal High Hazard Coastal A Zones(which are not
Area requirements to Coastal A Zones if Limit of Moderate Wave defined in the NFIP regulations).
Action (LiMWA) is delineated on FIRMs.
Definition ASCE 24-14,Section 1.2 Definitions. Equivalent to NFIP 44 CFR
"Breakaway Wall-Any type of wall subject to flooding that is §59.1 definition.
not required to provide structural support to a building or other
structure and that is designed and constructed such that, under
base flood or lesser flood conditions, it will collapse under
specific lateral loads in such a way that(1) it allows the free
passage of floodwaters and (2) it does not damage the structure
or supporting foundation system" (used with permission from
ASCE).
Change from ASCE 24-05: No change.
Breakaway ASCE 24-14,Section 4.6.1 Breakaway Walls. Exceeds NFIP 44 CFR
walls Requires breakaway walls to fail before or during base flood §60.3(e)(5)by specifying that
conditions without imparting loads on foundations and utilities and equipment must not
without producing damaging debris. Specifies that utilities to be mounted on, penetrate, or
and equipment must not be mounted on, pass through, or be be located on breakaway walls
located along breakaway walls. in Zone V or Coastal A Zones.
Change from ASCE 24-05: No change.
NFIP TECHNICAL BULLETIN 9 SEPTEMBER 2021 11
Table 2: Comparison of Selected 2021 IBC and ASCE 24-14 Requirements with NFIP Requirements(cont.)
ee a a• a 0 0 s 0 " 1 clie, ck � r�l� a®® ;aelu'�
Openings ASCE 24-14,Section 4.6.2 Openings in Breakaway Walls. Exceeds NFIP 44 CFR
Requires flood openings in breakaway walls to allow the §60.3(e)(5)by requiring flood
automatic entry and exit of floodwater. Refers to flood opening openings in all breakaway walls
requirements in ASCE 24, Section 2.7. in Zone V and Coastal A Zones
Change from ASCE 24-05: Modified to require flood openings in (see Section 3.3 of this Technical
breakaway walls, replacing a permissive statement. Bulletin).
Access ASCE 24-14,Chapter 8.1,General. Exceeds NFIP 44 CFR
stairways and Requires walls enclosing stairways and ramps to meet the §60.3(e)(5)by specifying
ramps requirements for enclosures in ASCE 24, Section 4.6. requirements for stairways
Change from ASCE 24-05: No change to enclosure and ramps in both Zone V and
requirements. Coastal A Zones.
Equipment ASCE 24-14,Section 7.1 General. Exceeds NFIP 44 CFR
(attendant Specifies requirements for elevation or design of building §60.3(e)(5)by specifying
utilities) equipment and utilities. Requires attendant utilities and that components must not
equipment to not be mounted on, pass through, or be located be mounted on or penetrate
along breakaway walls. through breakaway walls in
Change from ASCE 24-05: No change. Zone V or Coastal A Zones.
Equipment 2021 IBC Section 1402.7 Flood resistance for coastal high- Exceeds NFIP 44 CFR
electrical, hazard areas and coastal A zones. §60.3(e)(5)by specifying
mechanical, Specifies that electrical, mechanical, and plumbing system that components are not to
plumbing) components must not be mounted on or penetrate through be mounted on or penetrate
exterior walls that are designed to break away. through breakaway walls.
Change from 2018 to 2021 IBC: No change.
Change from 2015 to 2018 IBC: No change.
Change from 2012 to 2015 IBC: No change.
3.3 Flood Openings in Breakaway Walls
Observations after flood events indicate that breakaway walls with flood openings (see Figure 2) help minimize wall
failure in frequent, shallow flood events. Flood openings allow the automaticc inflow and outflow of floodwater,which
equalizes hydrostaticc forces on enclosure walls. Avoiding frequent wall failure reduces the amount of flood-borne
debris and protects enclosure interiors and stored items from wind-driven rain and sand. In addition, owners avoid
the cost and inconvenience of replacing walls.
The 2015 and later editions of the IRC and the 2014 edition of ASCE 24 require flood openings in breakaway walls in
both Zone A(including Coastal A Zones) and Zone V. Breakaway walls with flood openings must be designed to fail
under the base flood specified by the NFIP regulations and building codes and standards.
The NFIP regulations do not require flood openings in breakaway walls of enclosures below elevated buildings in
Zone V but require flood openings in walls of enclosures below elevated buildings in Zone A, even when breakaway
walls are specified. See NFIP Technical Bulletin 1, Requirements for Flood Openings in Foundation Walls and Walls of
Enclosures.
12 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
q
l E} '1(}�)i
�+Z
o rjolstt'tru
rr?t},r}�r
r2S,4{,� t -
3I r �y� Floor
9r1 adiLf f t i,` 4is S s �� E )ytr
1�tJ`� support
Breakawaybeambeam
wall
son
Each flood
opening no more than Vertical foundation member
I font above grade
Figure 2: Flood openings in breakaway walls
4 NFIP Flood Insurance Implications
Careful attention to cornpliance with the NFIP requirements for enclosures below elevated lowest floors is important
during the design, plan review, construction, and inspection of buildings in Zone V (Coastal High Hazard Areas).
Compliance influences vulnerability to flood damage and the cost of NFIP flood insurance premiums. Meeting
the minimum NFIP floodplain management requirements for enclosures does not necessarily result in the lowest
NFIP flood insurance premium. Designers and owners should consult an insurance agent familiar with NFIP flood
insurance to determine the insurance implications of design and construction decisions.
The NFIP floodplain management regulations in 44 CFR§ 60.3(e) allow open wood lattice-work, insect screening,
and solid, non-load-bearing, breakaway walls below elevated buildings in Coastal High Hazard Areas. For NFIP
flood insurance purposes, breakaway walls below elevated buildings do not qualify a structure to be classified as
"without enclosure." See NFIP Technical Bulletin 5, Free-of Obstruction Requirements, for more information on the
NFIP free-of-obstruction requirements.
Designers and owners should be aware of the following regarding NFIP flood insurance premiums for buildings in
Zone V with enclosures:
• Premiums for elevated buildings with enclosure,with or without breakaway walls, are higher than premiums for
elevated buildings that have no enclosed areas underneath.
• Buildings may be classified as without enclosure and may have lower premiums if the space below the lowest
elevated floor is enclosed in one of the following ways:
Insect screening,provided that no additional supports are required for the screening
Wooden or plasticc lattice with at least 40 percent of its area open and made of material no thicker than 1/2 inch
Wooden or plasticc slats or shutters with at least 40 percent of the area open and the slats or shutters made of
material no thicker than I inch
NFIP TECHNICAL BULLETIN 9 SEPTEMBER 2021 13
One solid breakaway wall or garage door with the remaining sides of the enclosure constructed of the above-
mentioned insect screening,wooden or plasticc lattice, slats, or shutters
• NFIP flood insurance policies have coverage limitations for enclosures and for contents below the lowest elevated
floor for post-FIR.iXI buildings in most SFHAs.
5 Wave Loads on Building Elements
Buildings in areas where conditions produce breaking waves are exposed to different and more severe loads than are
imposed on buildings in flood hazard areas without breaking waves. As a breaking wave passes a pile foundation or
other element of an open foundation, the structure is subject to an oscillating high-velocity water flow that peaks
at the wave crest just as the wave breaks. Drag forces are imposed on the relatively narrow vertical surfaces of open
foundations as water moves under the building and past the foundation elements, while most of the flow is relatively
undisturbed. Water flows past pilings and columns supporting elevated buildings in much the same way that rivers
flow past the piles and piers that support bridges. These forces are why open foundations are required in Zone N,
which is subject to high-velocity wave action. Open foundations are recommended in other flood hazard areas where
waves occur or that are exposed to high-velocity flows.
The effects of waves on buildings and foundations are quite different when a breaking wave hits a continuous,vertical
surface such as a wall that is wider than a column or piling. When the crest of a breaking wave impacts a wall, the
wave traps and compresses a pocket of air (see Figure 3). As the air pocket collapses, an exceedingly high-pressure
burst (i.e., shock wave) impacts the wall with the force centered around the Stillwater level. Peak pressures from a
5-foot breaking wave can be 100 times greater than the maximum design safe loading resistance (ultimate load) of
33 psf that is used in the prescriptive design method (see Sections 7 and 8 in this Technical Bulletin). Waves can also
"run up" the vertical face of the building above the BFE until the breakaway wall breaks away. The impact of waves
running up breakaway walls underneath buildings until the breakaway walls fail is discussed in Section 11.6 of this
Technical Bulletin.
Non-breaking and broken Xti ayes, Xti hich are waves that
BFE Wave cast
move along the surface of the water, represent an additional
design consideration for coastal structures. The effect
of non-breaking and broken waves should be a design
consideration inland from the open shore where breaking
waves are less frequent. Though less powerful than o--
breaking waves, non-breaking and broken waves can cause Stiller elevation
significant damage when impacting a vertical surface such Center of high-pressure burst
as a wall. When non-breaking and broken waves impact Air trapped and compressed
tical
a vertical surface, the wave can "run up" the surface, by breaking gave surface
dramatically increasing the flood load on the surface.
Ground
Figure 3: Impact of a breaking wave on a vertical surface
14 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
6 Breakaway Wall Performance
Breakaway wall performance has been evaluated by observing the condition of buildings in areas affected by coastal
storms (see Section 6.1 of this Technical Bulletin) and by testing performance in a laboratory (see Section 6.2 of this
Technical Bulletin). Conclusions from the observations are that most breakaway walls performed as intended when
designed and constructed in compliance with the NFIP regulations and that many elevated structures were damaged
or collapsed when the breakaway walls that surround areas under the building did not comply with the breakaway
wall requirements (FEMA, 2018b). The laboratory tests showed that wood-framed breakaway walls that are designed
to resist extreme wind conditions fail reliably at the connection between the bottom plate of the wall and the floor
(Tung et al., 1999).
.1 Observations of Breakaway Wall Performance
FEMA deploys Mitigation Assessment Teams (MATS) after some disasters to evaluate the performance of buildings
and related infrastructure. MAT reports prepared after significant coastal storms have consistently concluded
that breakaway wall systems perform as intended when they are designed and constructed to break away without
damaging the elevated building (FEMA, 2018b2). Additionally, properly constructed breakawav walls have not
been observed to become sufficient debris that causes significant foundation damage when trapped under buildings.
Figure 4 and Figure 5 are examples of successful breakaway wall performance.
� k s
i
SSS
3 t
�t
FNI �I yy "
o
Figure 4: Breakaway walls under an elevated building that were removed by waves(i.e., performed as
intended)during Hurricane Ivan in 2004(Gulf Shores,AL)
2 For additional MAT reports with observations of breakaway wall performance,see the FEMA Mitigation Assessment Team webpage at https://www.
fema.aov/emeraencv-manaaers/risk-manaaement/buildina-science/mitiaation-assessment-team.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 15
ik
y � !
1 _
i UUtt yy�
k
I}
1NI
11�7�i,
i
` o
-
- r m
. t
Figure 5: Unreinforced masonry breakaway walls removed by waves
(i.e., performed as intended)during Hurricane Irma in 2017(Monroe County, FL)
MAT reports also show that many of the breakaway walls that were designed, constructed, or modified in ways that
conflicted with the NFIP regulations led to unnecessary damage to, or collapse of, elevated structures. The most
commonly observed problems in breakaway wall systems were caused by poor detailing, inappropriately constructed
additions, and problems with other construction features. Such practices do not comply with the NFIP regulations,
which require structures to be "constructed by methods and practices that minimize flood damage" (44 GFR
§ 60.3(a)(3)).
Figure 6 through Figure 10 are examples of non-compliant construction practices identified during field assessments
for MAT reports.
Figure 6 shows damage associated with wave runup on walls that were not sufficiently detailed to break away from the
structure. To be compliant with the NFIP regulations, the breakaway wall that forms the enclosure must be designed
to break away cleanly from the structure and avoid continuous exterior sheathing spanning the breakaway walls and
the structure. See Section 8.3 of this Technical Bulletin for more information on appropriate separation joints.
Figure 7 shows propagation of damage to the building exterior above the lowest floor system,which was likely caused
by a lack of a horizontal separation joint between the breakaway wall and the wall above.
16 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
4t
-
,�
i4 k`
Y J{4 4Y
S PPP
I 1
r
Is
m
, 4v
t { r
Mm
t�I
Figure 6: Damage caused by waves running up the exterior wall prior to dislodging of
breakaway walls during Hurricane Ivan in 2004(Pensacola Beach, FL)
r -
� I
S A�T
r �tI
:WSJ AO
"IM
E
tt{1`z* t sJA a 4q}P t 0 +Jst ;ii r1 a`t9°J {
Svxl�6iv ut t �.3t �fSw�`�ii`<ia'in .!,fix tfit CS, .?ts'F}r{,r ,-WIN, {St, CS le, -. t�v'1 y�,t•' !,
Figure 7: Non-compliant joint detailing, resulting in the propagation of damage above the
lowest floor when the breakaway walls broke away during Hurricane Ike in 2008(Seabrook,TX)
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 17
Figure 8 illustrates what is likely to be the most common practice that contributes to darnage: poor detailing. In this
example, utilities attached to breakawav walls may have prevented the walls from breaking away. Similar damage is
caused when utility lines are run through improperly placed access holes (blockouts). All utility components that must
be installed below the elevated structure must be flood damage-resistant, designed for flood forces, and attached to
permanent structural elements. When utilities must be located below an elevated structure, the components should be
placed on the protected side of a foundation member on the side opposite to the anticipated direction of flow and wave
approach.
Figure 8: Utilities attached
to breakaway walls that may
have prevented the walls (
from breaking away, resulting r
in additional damage to the
structure during Hurricane Ike ks I
in 2008(Galveston Island,TX)
y
AU
Figure 9 shows cross bracing that had been installed inside breakawav
walls and that may have prevented the walls from performing as 6
intended and as required. When bracing is required by the structural
design, it must be located and installed so it does not interfere with the
intended performance of breakawav walls(see Technical Bulletin 5).
Figure 10 shows a detailing practice in which the breakawav walls
spanned vertical foundation members, which unintentionally
strengthened the breakawav walls and prevented them from
performing as intended.
tom,
i
CIS
Figure 9: Cross bracing that interfered with
the failure of a breakaway wall
18 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
Figure 10: Non-compliant
breakaway walls that were
nailed over the piles and floor
m beam, preventing a clean break
during Hurricane Ike in 2008
(Gulf Shores,AQ
�s } ��
}
a�
_t t �)1n41t �K
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4
.2 Research on BreakawayII Performance
Early analyses of breakawav walls assumed base flood conditions and oscillating (non-breaking) wave conditions.
The assumptions in research conducted by North Carolina State University and Oregon State University differed
in two significant ways to better model coastal storm conditions: rising water levels with time and breaking wave
conditions(Tung et al., 1999). In addition to the modeling,full-scale wall panels were tested in a wave tank to confirm
the theoretical results of the modeling.
Tung et al. (1999) found that walls constructed using standard wood studs and structural wood sheathing failed
after being hit by several breaking waves averaging less than 2 feet in height. Equivalent wave conditions usually
occur early in coastal storms when the Stillwater depth is approximately 2 feet above ground. Although the flood
forces acting on walls are significant, when the Stillwater depth is shallow, the forces are expected to act close to the
ground where much of the force is transferred into the ground or to the foundation near the ground. Since the loads
experienced prior to failure of a properly designed and constructed breakawav wall are applied near the bottom of the
wall,the forces that are transferred upward to the elevated building are minimized.
The tests on full-scale wall panels showed that wood-framed breakaway walls that are designed to resist extreme
wind conditions fail reliably at the connection between the bottom plate of the wall and the concrete slab depending
on fastening (see Figure 11). The tests showed that the failure begins with bowing and gradual displacement of the
bottom plate and that a similar secondary failure occurs beginning with the central studs of the breakaway wall(Tung
et al., 1999).
The tests determined that another secondary failure mode can occur if the bottom plate of the wall does not break
away. In this case,with only a slight increase in the applied load,failure occurs at the connection between the bottom
plate of the wall and the bottom of each wall stud (see Figure 12). The researchers concluded that properly detailed
and fastened wood-framed breakaway walls will effectively fail before the excessive loads imposed by greater wave
forces are transferred to the elevated building or foundation(Tung et al., 1999).
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 19
Figure 11: Expected failure mode
of wood-framed breakaway wall Wave force
based on full-scale testing
Nave orest',
�E
. -footr
minimum '
r
Stillwater wave height
elevation
Breakaway wall
Exterior sheathing
Vertical foundation
member— m Bottom plate
Permanent 2x4 Failure of nails
nailer plate holding bottom
m - plate to nailer plate
Ground
concrete slab
Failure of connection between
breakaway wall bottom plate
and permanent 2 4 nailer plate
Figure 12: Secondary failure
mode of wood-framed Wave force
breakaway wall as determined Wave crest
from full-scale testing
1,5 foot r'
minimum
r
wave height
Stillwater
elevation ''
`® w Breakaway wail
Exterior sheathing
Vertical foundation
member
Exterior sheathing
Failure of nails broken at bottom of
holding studs to breakaway wall studs
bottom plate
Bottom plate
Ground
„?
r Frangible concrete slab
"
Failure of connection between
Permanent 2x4
� ,'��� bottom of breakaway wall studs
nailer plate and breakaway wall bottom plate
20 INFIX TECHNICAL BULLETIN 9 SEPTEMBER 2021
Similar research on the performance of steel stud-frarned breakaway walls and unreinforced rnasonry breakaway
walls has not been conducted. If detailed properly, steel stud-framed breakawav walls are expected to fail in a manner
that is similar to wood-framed breakawav walls. Unreinforced masonry breakawav walls are expected to fail at the
mortar joints between the unreinforced ungrouted masonry units. Failure is expected to begin near the Stillwater level
where the pressure on the wall is assumed to be greatest(see Figure 13).
Figure 13: Expected failure mode of
unreinforced masonry breakaway wall
Wave farce
Wave crest
r
+ Ungrouted, hollow.
concrete masonry units
i. -foot
minimum
Stillwater wave height
elevation
r
a
Breakaway walls constructed
of unreinforced, hollow,
Vertical foundations concrete masonry units
member
_-Ground i nd Frangible concrete slab
i y 1h'g
I
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 21
7 Design Methods for Breakaway Walls
The NFIP regulations specify that buildings in
Zone V must resist the effects of wind and water loads FLOOD OPENINGS
acting simultaneously on all building components (where IN BREAKAWAY WALLS
applicable, seismicc loads must also be addressed). The NFIP does not require flood openings
The NFIP regulations further specify that breakaway walls in breakaway walls under elevated buildings
may be designed and constructed with either: in Zone V, but state or local governments
may. ASCE 24-14 and the 2015 and later
• A design safe loading resistance(ultimate load) of not editions of the I-Codes require flood
less than 17 psf and no more than 33 psf;,'3 in which openings in all breakaway walls, including
case a registered professional engineer or architect is in Coastal A Zones and Zone V. See
not required to certify the design. This method is the Section 3.3 of this Technical Bulletin.
prescriptive design method that is described in Section 8
of this Technical Bulletin.
• A design safe loading resistance(ultimate load)that exceeds 33 psf,provided a registered professional engineer or
architect certifies that the design meets certain conditions. To help the registered professional engineer or architect
certify the conditions, the simplified and performance-based design methods are described in Sections 9 and 10 of
this Technical Bulletin, respectively.
The intent of the breakaway wall requirements is to minimize loads on the foundation and the elevated building
during a base flood or larger event. The loading requirements for the design of breakaway walls are those that would
occur during the base flood. Even in communities that require buildings to be elevated higher than the minimum
elevation (with freeboard), the loads associated with the base flood must be used for breakaway wall design. If the
loads associated with a higher flood elevation are used, breakawav walls may not fail under a base flood conditions,
which could transfer additional loads to the foundation and would not comply with the NFIP requirements.
The placement of non-structural fill below and around elevated buildings should comply with Technical Bulletin 5.
Nonstructural fill material is not allowed to be placed against breakaway walls that are designed and constructed
using the prescriptive and simplified design methods. If non-structural fill material is placed against breakawav walls,
the walls must comply with the performance-based design method.
Table 3 summarizes the differences between and the limitations of the prescriptive, simplified, and performance-
based design methods for breakaway walls.
Careful plan review and inspection by local officials are paramount when the prescriptive and simplified design
methods are used. Plan reviewers must ensure that the proper number and type of connectors are specified for both
the top and the bottom plate connections, and inspectors should pay close attention that the installation complies
with the approved plans. Some jurisdictions may require a registered professional engineer or architect to verify the
number and type of connectors for the breakaway wall design prior to plan submittal.
3 These values reflect the adjustment that is necessary to reflect the current wind design approach and are equivalent to the NFIP regulations of not
less than 10 psf and no more than 20 psf.See Section 1.2 of this Technical Bulletin.
22 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
Table 3: Parameters for Breakaway Wall Design Methods
+''fV��lj�t 11 'j�l'4`�(�4'�11j1' IY4�����i a• a' 1• a
o 4 ''Vj�li °o'yip
Be a cs s ee®e' c.e e, a a
Prescriptive Not to exceed 120 mph Not less than 17 psf and 8 to 12 feet 6 to 9 feet
no more than 33 psf
Simplified 120 to 170 mph for More than 33 psf but 8 to 12 feet 6 to 9 feet
wood and steel-stud no more than 70 psf
120 to 150 mph for More than 33 psf but 8 to 12 feet 6 feet to
unreinforced masonry no more than 55 psf 8 feet 8 inches
Performance- Based on project Based on project Specified by Specified by
based location location designer designer
WINDOWSIN BREAKAWAY WALLS
Windows and doors are allowed in breakaway walls provided they do not interfere with the performance
of the walls and meet applicable building code requirements.
Any glazed openings in breakaway walls must meet the same windborne debris protection requirements
that apply to the building because buildings can be affected by high-wind events without flooding.
Windows and doors in breakaway walls are allowed when using the prescriptive and simplified design
methods provided the following requirements are met:
• For framed (wood or steel-stud) breakaway walls, windows and doors do not interfere with the ability of
the breakaway wall to break away during a flood event.
• The opening framing is not attached to the permanent nailers and is located such that the framing does
not need to be attached to foundation piles or columns.
• The bottom permanent nailer for the doorway opening is optional, and the door framing needs to be
attached to the breakaway bottom framing, not the permanent bottom nailer.
Windows and doors may be incorporated into the performance-based design method provided all of the
other design requirements are met.
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 23
8 Prescriptive Design Method
for Breakaway Walls
Walls with a design safe loading resistance (ultimate load) of not less than 17 psf and no more than 33 psf rneet the
NFIP requirements and can be designed and constructed using the prescriptive breakaway wall method. They do not
require certification by a registered professional engineer or architect. The intent of the prescriptive design method
is that when designing the foundation elements to resist flood loads, designers consider the loads associated with
breakaway walls until the breakaway walls fail during a base flood event at which point the breakaway walls are no
longer considered.
Tung et al. (1999) shows that breakaway walls with a design safe loading resistance (ultimate load) of no more than
33 psf will fail at very low flood loads (i.e., 1.5-foot wave height). Failure at no more than 33 psf ensures that the
foundation and building can be designed to accommodate wind, flood, and debris impact loads transferred from
breakaway walls up to the point of wall failure and that beyond this threshold, the foundation loads will be reduced
by the elimination of loads from the breakaway wall. However, the 33 psf restriction may not accommodate all of
the necessary loading requirements on a breakaway wall from wind, seismic, or debris impact loads. It was never the
intent to allow breakaway walls to be designed for less than the building and residential code-mandated wind and
seismic.loads. The applicability of this prescriptive design method is based on a combination of the site characteristics
and pile spacings outlined in Section 8.1 of this Technical Bulletin.
Breakaway walls that are built in accordance with the prescriptive design method are considered to have a design safe
loading resistance (ultimate load) of not less than 17 psf and no more than 33 psf. Modern building and residential
codes used along the Gulf and Atlantic. Coasts are likely to require unfactored design wind pressures that exceed 33
psf;which prohibit the use of the prescriptive design method. Designers may not use the prescriptive design method in
areas where design wind pressures exceed 33 psf and should evaluate the applicability of the simplified design method
and the performance-based design method.
.1 Applicability
Wood-framed, steel stud-framed, and unreinforced masonry
breakaway walls that use the prescriptive design method do not WIND LADS
require certification by a registered professional engineer or
The prescriptive design method for
architect and are permitted if all of the following conditions are
satisfied: breakaway walls may not be used in
areas where the wind loads exceed
• Breakaway wall heights are between 6 and 9 feet, and piles base flood loads for breakaway walls.
or columns are spaced between 8 and 12 feet apart. (The The prescriptive design method is
performance-based design method must be used when the applicable only when wind loads do
conditions fall outside these parameters; see Section 10 of this not exceed base flood loads.
Technical Bulletin.)
• The 3-second gust design wind speed for all parts of breakaway
walls does not exceed 120 mph per the basic wind speed maps in ASCE 7-16. The 3 second gust design wind
speeds for a specificc location can also be obtained from the Applied Technology Council website hops hazards.
atcouncil.org-.As with any design,the enforced design wind speeds for specificc locations should be verified with
local officials.
24 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
• The prescriptive design method for wood-framed and steel stud-framed walls is permitted for all Seismic Design
Categories in ASGE 7-16. Unreinforced masonry breakaway walls are permitted only in Seismic Design Category
A as identified in ASGE 7-16.
• Breakaway walls serving as backup for brick veneer or other material that may be damaged by excessive deflections
may not be designed using the prescriptive design method.
.2 Design Methodology
Wood-framed breakaway walls must be constructed in accordance with
Figure 14. Nail requirements for wood-framed breakaway walls are listed STEEL STUD-FRAMED
in Table 4.Wood-framed breakaway walls must be constructed using flood BREAKAWAY WALLS
damage-resistant, No. 2 Grade Spruce-Pine-Fir or better grade/species The section designation (type,
(e.g.,No. 2 Southern Pine has a greater allowable bending stress). gauge, and size)for steel stud-
Steel stud-framed breakaway walls must be constructed in accordance framed breakaway walls in
with Figure 15. Screw requirements for steel stud-framed breakaway walls the prescriptive and simplified
are listed in Table 5. Interpolation for different pile spacings and wall design methods is provided in
heights is permitted when using Table 4 and Table 5. Utility blockouts Figure 14 and Section 9.2 of
should be located in the upper corners of breakaway wall panel sections this Technical Bulletin.
and sized to allow clear passage of the utility based on building material
sizing (e.g., masonry block sizes). A 4-inch by 4-inch utility blockout is
shown in Figure 14 for wood-framed breakaway walls and in Figure 15
for steel stud-framed breakaway walls, and an 8-inch by 8-inch utility blockout is shown for unreinforced masonry
breakaway walls in Figure 20. The size of utility blockouts should be as small as possible to minimize the impact to
the performance of the breakaway wall.
PRESCRIPTIVE AND SIMPLIFIED BREAKAWAY WALL DESIGN METHOD ASSUMPTIONS
In both the prescriptive and simplified design methods, breakaway wall panels are designed to fail
under a non-breaking or broken wave loading condition.A stillwater depth of 1.9 feet and a 1.5-foot-tall
non-breaking wave are assumed to ensure that the panels could be incorporated into Coastal A Zone
buildings. The wall is assumed to have flood openings that equalize hydrostatic loads, and a flood velocity
of 4.9 feet per second is assumed.The conditions also assume wave runup on the breakaway wall
exterior surface.
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 25
Figure 14:Typical wood-framed breakaway wall
construction (prescriptive design method); see Permanent 2x4 nailer
Table 4 for nail requirements for top and bottom
(no nails along panel sides) Beam
mn
4-inch x 4-inch-
utility blockout ] 4.
1 --Breakaway 2x4
@24 inches o.c.
Exterior }'
a r'fi sheathing p ;? Nails per Table 4
�` 6t
Three 16d toe nails
(typical)
77, �
Buildup Breakaway 2x4
��' 2x4 f (typical)
K rarrain
Y
1 t v3 1:u
Frangible concrete slab
f
.4rL " Permanent 2x4.nailer
26 IN IP TECHNICAL BULLETIN 9 SEPTEMBER 2021
Table 4: Required Size and Number of Galvanized
Common Nails for Wood-Framed Breakaway Walls
with Different Heights and Pile Spacings
• e e e �, a ®e
6 8 8d 18
10d 12
10 8d 24
10d 16
12 8d 28
10d 18
7 8 8d 22
10d 14
10 8d 28
10d 18
12 8d 32
10d 22
8 8 8d 24
10d 16
10 8d 32
10d 20
12 8d 38
10d 24
9 8 8d 28
10d 18
10 8d 34
10d 24
12 8d 42
10d 28
(1) Divided equally between top and bottom and evenly
spaced;nails must not be used along panel sides
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 27
Figure 15:Typical steel stud-framed breakaway
Permanent 20 nailer wall construction with designated section type,
gauge,and size (prescriptive design method);see
Beam Table 5 for screw requirements. Note that two
no.6 screws are shown as a diagonal connection
4-inch x 4-inch for clarity;the typical connection location is
utility blockcut ! between the flanges of the steel stud and steel
ilk
� K Breakaway track.
1,
362S162 33
Exterior
Gap i sheaths Screws per Table 5
{
Two no. 6 screws
1,t (typical)
Build-up Breakaway
t}s3 framing 362T150-27
\it
y Frangible concrete slaty
Permanent 2x4 nailer
Table 5: Required Number of 1-inch-long No.
6 Self-Tapping Screws for Steel Stud-Framed
Breakaway Walls with Different Heights and
Pile Spacings
• e , a e
6 8 22
10 28
12 32
7 8 26
10 32
12 38
8 8 30
10 36
12 44
9 8 32
10 42
12 50
(1) Divided equally between top and bottom and
evenly spaced and conforming to SAE J78 with a
Type II coating in accordance with ASTM B 633
(screws must not be used along panel sides)
28 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
8.2.1 Unreinforceds siOption
The prescriptive design method for unreinforced masonry breakawav walls is the same as the simplified design
method (see Section 9 of this Technical Bulletin). The unreinforced masonry wall failure mode is such that it will fail
under a base flood condition and resist a wind load of up to 55 psf or a wind speed of 150 mph. Unreinforced masonry
breakaway walls were developed to be used only in Seismic Design Category A, as defined in ASCE 7-16.
Unreinforced masonry infill breakawav walls must be constructed in accordance with the following building
configurations:
• Lowest horizontal structural member is a concrete beam(see Figure 16)
• Lowest horizontal structural member is a timber structural beam with floor joists bearing on the structural beam
(see Figure 17)
• Lowest horizontal structural member is a timber structural beam with floor joists hanging from the face of the
structural beam(see Figure 18).
Note that the sheathing material shown
in Figure 16, Figure 17, and Figure 18
incorporates a 4-inch overlap of the top of
the masonry breakaway wall to help restrain Typical wall
sheathing nail on
the wall until it is knocked free by a base each side ref Joust
ti
flood event. This section of sheathing
is detailed to terminate at the top with
a watertight seal at the midpoint of the
rim Joist of the elevated building. This joint Watertight separation
J 5 joint at mid-point of
overlap detail prevents damage to the rim joist '
elevated building but provides sufficient
attachment surface for the sheathing during
construction. 4 inches
Wall sheathing wall
Wall bottom plate:
Pbwood floor
Rare joist Floor joist
Sill plate
ebeam4 inches ,,,.IConcr
2A attached to
concrete beam
Unreinforced and—a• _-16d nail(typical)
ungrouted 8-inch per Table 6
CMU with Type N
mortar Frangible
First course to be concrete slab
bonded to concrete ( C
with Type N mortar
;.W . . V.
Figure 16:Typical breakaway masonry wall where the lowest horizontal
structural member is a concrete beam (prescriptive design method);see
Table 6 for nailing requirements
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 29
n- tip
Watertight
separation joint ,
at midpoint of 1l),
structural beam
Typical wall
sheathln nail 3.
� 3� i
on each serfs
ofjoint flinches W
bs
U7.
Wall sheatIung Wall all sheathing—se Wall
Plywood Hoar
Blocking 16 inches o.c.
Wall,bottom platee � � GII bsttarrr platy � � same size as floor joists
Plywood ifarir
Rim joist- d Floor joist Rim joist
Structural 4 Inches t
beam __ Floor joist
16d nail(typical)per Table 6 Additional CMU block Yp[16d nail(typical)per Table 6
4 inches above typical wall height �
Nominal 2x timber hoard. with structural beam Nominal 2x timber board.
Unreinforced and .,, r Board to be 2 inches wider Board to be 2 inches wider
un routed B-inch CMU than structural beam, Unreinforced and s.-
g ungrouted$inch CMU than structural beam
with Type N mortar with Type N mortar
f'Franguble concrete slab Frangible concrete slab..
First course to be First course to be -
bonded to concrete bonded to concrete
—')
with Type N mortar , a° :` n .- ," wath Type N mortar
Figure 17:Typical breakaway masonry wall where the lowest horizontal structural member is a timber structural beam with floor joists
bearing on the structural beam(prescriptive design method).Left image is perpendicular to the floor joists,and the right image is normal
to the floor joists;see Table 6 for nailing requirements.
30 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
Watertight
separation faint
at mid-paint of
structural beam y
t
Typical wall
sheathing
pall on each
side of joint
4 inches
Wall
Wall sheathing Wall
,r Plywood floor
all sheathing r /✓ Blacking 16 inches a.c.
Wall bottom plate ��" same size as floor foists
Wall bottom plate _
Plywood floor Rim foist
Structural 4 inches °.°.°..°......�
beam Froorjmst
16d nail(typical)
16d nail(typical) per Table 6
Unreinforced a per Table 6 Unrem#arced.•....................a
2x4
and ucgrouted and ungrouted
S-inch CMU with 2x4 S-inch CMU with
Type N mortar Frangible Type N mortar Frangible concrete stab
First course to be— � concrete slab First course to be—
bonded to concrete I bonded to concrete
with Type N mortar with Type N mortar
�44
Figure 18:Typical breakaway masonry wall where the lowest horizontal structural member is a timber structural beam with floor
joists hanging from the face of the structural beam(prescriptive design method).Left image is perpendicular to the floor joists,
and the right image is normal to the floor joists;see Table 6 for nailing requirements.
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 31
Unreinforced masonry infill walls rnav be used in the prescriptive and sirnplified design methods onlv when the
dimensions of the openings align with masonry modular dimensions (i.e., the opening size is an even multiple of
8 inches). The configuration of the structural framing may impact the timber framing that is used to restrain the
masonry units. Table 6 indicates the nailing requirements for securing timber sections to the structure (interpolation
is allowed). Timber framing used as part of these breakaway wall systems must be constructed using flood damage-
resistant, No. 2 Grade Spruce-Pine-Fir or better grade/species (e.g., No. 2 Southern Pine has a greater allowable
bending stress).
Table 6: Required Number of Galvanized 16d
Common Nails for Restraining 2x4s on
Unreinforced Masonry Breakaway Walls
with Different Pile Spacings
6 feet 0 inch 8 7
10 9
12 10
7 feet 4 8 7
inches
10 9
12 10
8 feet 0 inch 8 7
10 9
12 10
8 feet 8 8 7
inches
10 9
12 10
(1) Divided equally along the top framing elements
32 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
8.3 Design Details
When using Section 8.3 of this Technical Bulletin for the prescriptive design method, designers should also reference
the tables and figures in Section 9.2 of this Technical Bulletin.
All breakaway walls designed using the prescriptive design method must be designed and detailed in accordance with
the following:
• Breakaway walls are designed to meet all applicable state and local building codes or other requirements.
• The material specifications match the material specifications shown in the figures and tables in this Technical
Bulletin(if not,the performance-based design method must be used)
• Per Figure 14 and Figure 15,wood-framed and steel stud-framed breakaway wall panels are not attached to
the pilings or other vertical foundation members. Only the tops and bottoms of wall panels may be connected
to permanent 2x4 nailer plates. High-capacity connectors such as bolts,lag screws,metal straps, and hurricane
fasteners(e.g., (,lips, straps) are not used to secure breakaway wall panels.
• Unreinforced masonry breakaway walls were developed to be used only in Seismic Design Category A, as defined
in ASCE 7-16. The following assumptions apply to the designs shown in Figure 16, Figure 17, and Figure 18.
Unreiuforced masonry blocks are bonded to the frangible concrete slab or grade beam and to each other using
Type N mortar conforming to AST'XI C270.
Concrete masonry units(C1VIUs) are 8-inch nominal units with a compressive strength of 2,000 psi.
XIasonry infill walls are used only when the dimensions of the openings align with masonry modular
dimensions.
There are no fasteners attaching the masonry to timber framing or connection to the concrete slab, grade
beam, or columns.
Where a concrete beam is used to support the elevated structure shown in Figure 16,mortar is not required in
the gap between the top masonry block in the wall and the bottom of the concrete beam.
• The exterior structure's wall siding/sheathing does not extend below the lowest horizontal structural member and
overlaps with breakaway wall panels(except as shown to comply with Figure 16, Figure 17, and Figure 18), and
breakaway wall panels do not overlap and are not attached to the vertical foundation members.
• Breakaway wall sheathing and siding are discontinuous at the lowest horizontal structural member;horizontal
separation joints are provided to prevent damage to the sheathing or siding above the lowest horizontal structural
member(see Figure 19).As shown in Figure 19, a watertight seal is provided for separation joints to prevent wind-
driven rain and sea spray from entering the building envelope. A similar vertical sealed joint may be needed in
front of the piling.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 33
E
E�
House walls Seated separation joint
and breakaway (see cutaway detail]
walls covered
with stucco
del d
�s� area
v 't,
t
A
Watertight
separation joint ..........Stucco
Lath for house wall at bottom of 1-4 Lath
1 . House.. lowest horizontal Sheathing
sheathing structural member
ti+ $ in accordance Bean
with local codes
Non breakaway " Beam Stucco-covered
house wall Separation,
construction joint
Breakaway � '1�°�t�tlN� 17i111}}}}�ti1tilF�i1 '' �
construction
:.r,U, �luli%i��ll��l�i Stucco-covered � s
f A I i breakaway �l�lr3ttz
Breakaway wall �� wall lath, h ��� Breakaway
Stucco,framing members r ( and sheathing wall framing
discontinuous members
Vertical foundation
5 at separation
member joint ;rt`
Breakaway wall
sheathing
Lath for breakaway wall
A Vertical foundation member
not shown for clarity
Section A-A
Figure 19:Separation joint between sheathing and wall covering (e.g.,stucco,siding)on house walls and breakaway walls
34 INFIX TECHNICAL BULLETIN 9 SEPTEMBER 2021
• Utilities,including electrical wiring, switches, outlets, breaker boxes,power rneters,plurnbing, conduits, and
ventilation ducts, are not mounted on or attached to breakaway wall panels. Building supply lines and other utility
fixtures, such as light switches and electrical outlets,may be attached to the sheltered side of vertical foundation
members as allowed by applicable building codes and floodplain management regulations(which generally require
utilities to be elevated above the BFE). If utility lines must be routed into or out of an enclosure, one or more of the
walls are constructed with a utility blockout(see Figure 14 and Figure 15). For unreinforced masonry breakaway
walls, the utility openings are 8 inches by 8 inches based on standard masonry block sizes(see Figure 20)but as
small as possible. Utility lines that pass through the blockout are independent of the walls and are therefore not
subject to damage if the wall panels break away.
• Breakaway wall panels are positioned such that, on failure,they do not collapse against cross-bracing or threaten
other foundation components(for more information, see Technical Bulletin 5).
• Partial-height breakaway wall systems using the prescriptive design method are not permitted. (Other methods can
be used, as described in Section 11.4 of this Technical Bulletin.)
When using the prescriptive design method for unreiuforced masonry, designers should reference the tables and
figures in Section 9.2 of this Technical Bulletin.
Sheathing Structural
bear
Y —watertight
tti separation joint
at mid-point of
t ) ( structural bear
8-inch X 8-inch
utility blockout
Vertical
foundation
element.
it r t i ' ' I��
��
+`N
�s5 �II
� ,
IJ�II'q
Frangible concrete to slab w;V,itS)ftiA
r
Figure 20: Utility blockout for an unreinforced masonry breakaway wall
INFIX TECHNICAL BULLETIN 9 SEPTEMBER 2021 35
8.4 Example
Problem: Design a 10-foot-wide by 9-foot-tall wood-frarned breakaway wall for a 3-second gust design wind speed
of 120 mph. The Seismic Design Category is D, and deflection of the wall is not important. Wood framing must be
constructed using flood damage-resistant material such as No. 2 Grade Spruce-Pine-Fir 2x4s or better grade/species.
Solution: The described problem clearly allows the use of the prescriptive design method. Due to the Seismic Design
Category, unreinforced masonry breakaway walls are not permitted, and wood-framed breakawav walls could
therefore be considered. Figure 14 shows that 2x4 studs at 24 inches on center (o.c.) must be toe nailed to the top
and bottom plates using three 16d nails. According to Table 4, 24 10d nails (12 top and 12 bottom) could be used to
connect the breakaway top and bottom plates to permanent 2x4 nailer plates.
9 Simplified Design Method
for Breakaway Walls
In most coastal areas, the applicable building codes include wind and/or seismicc design requirements that exceed
the maximum allowed design safe loading resistance (ultimate load) of 33 psf in the prescriptive design method
for breakaway walls. NFIP performance criteria allow breakaway walls that meet a design safe loading resistance
(ultimate load) that is more than 33 psf if a registered professional engineer or architect certifies that(1) the wall will
collapse before base flood conditions are reached and (2) the elevated building will not be damaged by combined
wind and flood loads acting simultaneously on all building components. The above performance criteria comprise the
simplified design method.
Breakaway walls designed in accordance with the simplified design method have a design safe loading resistance
(ultimate load) that exceeds 33 psf, yet they still comply with NFIP performance criteria. Tung et al. (1999) shows
that wave loads do not exceed the design capacity of elevated structures or their supporting foundations if breakawav
walls are designed to resist wind loads of up to 55 psf. Therefore, walls designed using the simplified design method
meet NFIP performance criteria. Stud, nail, and screw requirements in Table 7 through Table 10 meet the stringent
design conditions described in Section 9.1 of this Technical Bulletin. The quantity or size of fasteners may be reduced
as long as the designer ensures that the breakaway wall satisfies the adopted building code's wind and/or seismic.
requirements.
When wind pressures exceed 70 psf for wood-framed and steel stud-framed breakaway walls or 55 psf for unreinforced
masonry breakaway walls, the performance-based design method must be used (see Section 10 of this Technical
Bulletin).
.1 Applicability
The simplified design method for wood-framed and steel stud-framed breakaway walls requires certification by a
registered professional engineer or architect. The method may be used in all Seismic Design Categories identified in
ASCE 7-16 when all of the following conditions are satisfied:
• Breakaway wall heights are between 6 and 9 feet, and piles or columns are between 8 and 12 feet apart. The
performance-based design method must be used for configurations that are outside these limitations.
36 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
• The 3-second gust design wind speed for all parts of breakaway walls is between 120 and 170 mph per the basic
wind speed maps in ASGE 7-16. Wind pressures shall not exceed 70 psf.
• Breakaway walls do not serve as support for brick veneer or other materials that may be damaged by excessive
deflections.
The simplified design method for unreinforced masonry walls requires certification by a registered professional
engineer or architect. The method is permitted in all Seismic Design Categories identified in ASGE 7-16 when all of
the following conditions are satisfied:
• Breakaway wall heights are between 6 feet and 8 feet 8 inches, and piles or columns are between 8 and 12 feet
apart. The performance-based design method must be used for configurations that are outside these limitations.
• The 3-second gust design wind speed is between 120 and 150 mph in accordance with the basic wind speed maps
in ASGE 7-16. Wind pressures shall not exceed 55 psf.
• Breakaway walls do not serve as support for brick veneer or other materials that may be damaged by excessive
deflections.
.2 Design Methodology
Wood-framed walls must be constructed using flood damage-resistant Spruce-Pine-Fir or better species (e.g.,
No. 2 Southern Pine has a higher allowable bending stress). Wood-framed breakaway walls must be constructed in
accordance with Figure 21. Table 7 provides the required spacing for No. 2 Grade studs as a function of wind speed
and wall height. Stud spacing values may not be interpolated (e.g., use a 150-mph design wind speed if the actual
design wind speed is greater than 140 mph but less than or equal to 150 mph). Table 8 provides the required number
of nails for different design wind speeds as a function of wall height and pile spacing(interpolation is allowed).
Permanent 2x4 nailer Figure 21:Typical wood-framed breakaway wall
construction (simplified design method)
Beam
Inch x 4-inch ;}
utility blockout
} —Breakaway 2x4
0 i �L
t ,
i
F Exterior ; )
Gap sheathing Mails per Tab[e 8
of i�
1' Three 1d toe nails
(typical)
Ityp )
I' wild-up ` Breakaway 2x4
2x4 i (typical)
,=11 framing
Frangible concrete slab
� y
Permanent 2x4 nailer
INFIX TECHNICAL BULLETIN 9 SEPTEMBER 2021 37
EDGE DISTANCE, END DISTANCES,AND SPACING FOR TOE NAILS
Figure 21 shows that three 16d (3 1/2-inch)toe nails are required for all wall geometries.Although no
specific pattern of toe nailing is required in this Technical Bulletin, the National Design Specification
(NDS)for Wood Construction (AWC, 2018) requires that edge distances, end distances, and spacing be
sufficient to prevent splitting the wood. If horizontal construction is preferred by the contractor, one 16d
nail installed end grain to the stud may be used with two 16d toe nails installed in alternate directions
once the wall is placed vertically(see Figure 21). Likewise,two 40d nails installed end grain to the stud
may be used so the breakaway wall can be assembled horizontally and then nailed in place to the
permanent top and bottom nailer plates. Pre-drilling may be required.
Table 7: Required 2x4(No.2 Grade)Stud
Spacing for Wood-Framed Breakaway Walls of
Different Heights and Design Wind Speeds
le a s e
e a e•es ee " e, a
ee ® e
6 140 24
150 24
160 24
170 24
7 140 24
150 24
160 16
170 16
8 140 16
150 16
160 16
170 12
9 140 16
150 12
160 12
170 Not
permitted(')
(1) Where not permitted,performance-based design
method must be used for breakaway wall design
38 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
Table 8: Required Number of 10d Galvanized Common Nails for
Wood-Framed Breakaway Walls with Different Wall Heights and
Design Wind Speeds
le A {
6 140 8 18
10 20
12 24
150 8 20
10 24
12 30
160 8 22
10 28
12 34
170 8 26
10 32
12 38
7 140 8 20
10 24
12 30
150 8 22
10 28
12 34
160 8 26
10 32
12 40
170 8 30
10 38
12 44
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 39
Table 8: Required Number of 10d Galvanized Common Nails for
Wood-Framed Breakaway Walls with Different Wall Heights and
Design Wind Speeds(cont.)
e ® { ee
8 140 8 22
10 28
12 34
150 8 26
10 32
12 38
160 8 30
10 38
12 44
170 8 34
10 42
12 52
9 140 8 24
10 32
12 38
150 8 30
10 36
12 44
160 8 34
10 42
12 50
170 8 Not
permitted(2)
10
12
(1) Divided equally between top and bottom and evenly spaced(nails
must not be used along panel sides)
(2) Where not permitted,performance-based design method must be
used for breakaway wall design.
40 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
Permanent 2x4 nailer Figure 22:Typical steel stud-framed breakaway
wall construction (simplified design method)
Beam
4-inch x flinch
utility blockout �i
¢4 _Breakaway
362S162-33
lI? Exterior
li sheathing
Gap rt i Screws per Table 10
jl
Two no. 6 screws
' (typical)
1 Build-up Breakaway
t�" framing 362T150.27
_mz „
Frangible concrete slabj
Permanent 2x4 nailer
Steel stud-framed breakaway walls must be constructed in accordance with Figure 22. Table 9 provides the required
spacing for steel studs as a function of wind speed and wall height. Stud spacing values may not be interpolated
(e.g., use 150 mph design wind speed if actual design wind speed is greater than 140 mph but less than 150 mph).
Table 10 provides the required number of self-tapping screws for different design wind speeds as a function of wall
height and pile spacing(interpolation is allowed).
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 41
Table 9: Required 362S162-33 Stud Spacing
for Steel Stud-Framed Breakaway Walls with
Different Heights and Design Wind Speeds
fe e
6 140 24
150 24
160 24
170 24
7 140 24
150 24
160 24
170 16
8 140 24
150 16
160 16
170 12
9 140 16
150 12
160 12
170 Not
permitted0)
(1) Where not permitted,performance-based design
method must be used for breakaway wall design.
42 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
Table 10: Required Number of 1-inch long No. 6 Self-Tapping
Screws for Steel-Stud Framed Breakaway Walls with Different
Heights and Design Wind Speeds
fe {
6 140 8 30
10 36
12 44
150 8 34
10 42
12 50
160 8 40
10 50
12 60
170 8 46
10 56
12 68
7 140 8 34
10 42
12 50
150 8 40
10 50
12 60
160 8 46
10 58
12 70
170 8 52
10 66
12 78
NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021 43
Table 10: Required Number of 1-inch long No. 6 Self-Tapping
Screws for Steel-Stud Framed Breakaway Walls with Different
Heights and Design Wind Speeds(cont.)
fe {
ee ® { ee
8 140 8 38
10 48
12 58
150 8 46
10 56
12 68
160 8 52
10 66
12 78
170 8 60
10 76
12 90
9 140 8 44
10 54
12 66
150 8 50
10 64
12 76
160 8 60
10 74
12 88
170 8 Not
permitted(2)
10
12
(1) Divided equally between top and bottom and evenly spaced and
conforming to SAE J78 with a Type II
Coating in accordance with ASTM B 633
(2) Where not permitted,performance-based design method must be
used for breakaway wall design.
44 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
9.3 Design Details
The design details in the prescriptive design rnethod (see Section 8.3 of this Technical Bulletin) also apply to the
simplified design method.
9.4 Example
Problem: Design a 10-foot-wide by 9-foot-tall wood-framed breakaway wall for a 3-second gust design wind speed
of 160 mph. The Seismic Design Category is D, and deflection of the wall is not important. Wood framing is flood
damage-resistant No. 2 Grade Spruce-Pine-Fir or better grade/species.
Solution: The described problem allows the use of the simplified design method. According to Table 7, 2x4 studs at
12 inches o.c. must be toe nailed to breakaway 2x4 top and bottom plates using three 16d nails(Figure 21). According
to Table 8, 42 10d nails (21 top and 21 bottom) must be used to connect the breakaway top and bottom plates to
permanent 2x4 nailer plates.
10 Performance-Based Design Method
for Breakaway Walls
Breakaway walls designed in accordance with the performance-based design method will normally have a design safe
loading resistance(ultimate load) of greater than 33 psf. Flood loads(i.e.,wave loads,hydrodynamicc loads, and impact
loads) must be calculated and taken into account when designing the breakawav wall system, and once a design
condition is met, the designer should verify that the walls do not impart an additional load on the elevated structure
and the supporting foundation system. However, as described below the designer has slightly more flexibility when
detailing breakaway wall systems using the performance-based design method than in the prescriptive design method.
10.1 Applicability
The performance-based design method is always permitted, and the walls may be designed and constructed using
wood studs, steel studs, unreinforced masonry, or alternative materials. However, the anticipation is that the
performance-based design method will be used primarily when the applicability criteria (e.g., taller walls, wider
spans, higher design wind speeds, greater seismicc design category) for the prescriptive and simplified design methods
cannot be satisfied. The performance-based design method for breakaway walls must be performed and certified by a
registered professional engineer or architect.
10.2 Design Methodology
Breakaway walls must be capable of resisting the design wind loads on the building while still failing under base flood
conditions. The performance-based design method for breakaway walls consists of designing the breakaway wall to
resist the largest out-of-plane load of(1) the design wind pressure in accordance with ASGE 7, (2) the design seismic
out-of-plane load in accordance with ASGE 7, or (3) demonstrating a minimum resistance of 17 psf(ultimate load).
For masonry design, building codes and material standards no longer permit a one-third allowable stress increase
for resisting wind and seismic.forces. As a result, the one-third allowable stress increase is prohibited when designing
unreinforced masonry breakaway walls.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 45
Although breakaway walls are permitted by the NFIP regulations, the effects of flood loads on these walls (and any
other building components that are below the PFE) must be included in the design of the elevated structure and
its supporting foundation. Designers must evaluate two conditions when designing the building foundation: (1) a
design flood event on the foundation during a design event once the breakaway walls have failed and (2)just prior
to the breakaway walls' failing during a base flood event while breakaway walls are still attached to the building.
The foundation must be capable of resisting both of these loading conditions. It should be noted that more resistant
breakaway walls increase the potential forces from debris impact loading on foundation elements and possibly on
neighboring structures. Nave heights during both the design condition and the base flood condition should be
calculated based on the site conditions using a method such as the one outlined in FEIVIA P-55, Coastal Construction
Manual(2011).
An evaluation of buildings for base flood conditions should include whether exposure to non-breaking or broken
waves is expected because the design assumptions for non-breaking and broken waves are different from the
assumptions for breaking waves. While flood maps do not adequately indicate whether waves are breaking, non-
breaking, or broken, buildings along the shoreline without obstructions such as other buildings could be assumed
to be exposed to breaking waves. Buildings that are shielded by buildings or other significant obstructions should be
assumed to be exposed to waves that are either non-breaking or broken.
ASCE 7, Chapter 5, provides guidance on calculating breaking waves on vertical walls to address breaking wave
conditions. Non-breaking waves and broken waves must be addressed differently. A recommended approach when
designing for non-breaking and broken waves is to consider that hydrostaticc loads and hydrodynamicc loads will cause
the proposed breakaway wall to fail. Since a debris load cannot be relied upon to cause the wall to fail, a debris load
should not be considered in the design of breakaway walls. The hydrostaticc load should consider that the exterior wall
face will experience a wave runup height of 1.5 times the wave height above the Stillwater depth. The interior face of
the breakaway wall will likely experience a hydrostaticc load of approximately the Stillwater depth due to the potential
for flood openings on some buildings, but breakaway walls are often open enough along the sides of the wall that
equalization of the floodwaters to the Stillwater depth is likely. The hydrodynamicc load should be calculated using the
Stillwater depth and follow the guidance in the commentary for ASCE 7, Chapter 5, to calculate flood velocities and
the associated loads.
Using non-breaking or broken waves for analysis yields a wall system that will fail under lower loading and reduces
loads on the foundation system during the evaluation of the condition when breakaway walls are still in place and
fully loaded by the base flood condition just prior to the walls' failing. Even when breaking waves are expected, if
breakaway walls are designed using non-breaking or broken waves, the foundation is more likely to experience
reduced flood loading during a base flood event.
10.3 mted Breakaway Walls
A segmented breakaway wall that is designed using the performance-based design method can minimize the need to
replace an entire breakaway wall after a less than base flood event. As shown in Figure 23, a segmented breakaway
wall allows horizontal segments or sections of the wall to fail as floodwaters rise. Vertical segments are also allowed
provided they meet all other breakaway wall requirements. Each segment must meet the loading requirements
outlined in Section 10.2 of this Technical Bulletin in order to ensure that during a base flood condition, the wall
segments will fail and will not increase the loads on the foundation elements. Configuration details for segmented
breakaway walls are based on segment height,foundation element spacing, and loading requirements. Review Section
11.4 of this Technical Bulletin on partial-height breakaway walls to make sure that a proposed wall configuration is
compliant with the minimum requirements for breakaway walls.
46 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
Figure 23: Example of a segmented
Full height breakaway walls breakaway wall using horizontal
segments. Example elevations are
Lowest hcnzantal structural member---,,,, provided for clarity.
EL 1,0,0 Beet
�l i Ali
1, I�flly 1,,5)1 '�IIIs „{,,, .
'(1'1f3'1� i .�}) ,�I;�()
Timber
'I (I sif, \p »li?1s 111I1l1,1p
�?�1���,rJ\ }Its r1t�S lSsllll I���lit�}i�.1 s�1�s�H ile
BFE
�\ 6$�<I���,S�l�)
7s���1�sS
,ttl liiil»i�s; t
8.0
feet
_ Segmented
{ ! n,,, }„ s>> �S)}�sf� 11}�ii s ,.-: t�itVs! .t >'y. �lreakaway
\jrf 11�����h �fI J,a., '-�s�l�y 'tlillilll�s �Vrr;S s>s ss si\i rf yti{s} r s �f»>sj s
wall SeCt31?n
Edge of wallsegment/
ft
li
f' failure joint
EL 2.0 feet--
Frangible concrete slab Frangible concrete slab
v
round
10.4 DesignDetails
All breakaway walls designed using the performance-based design
method must be designed and detailed in accordance with the WIND LADS THAT EXCEED
following: FLOOD LADS
• Breakaway walls are designed to meet all applicable state and When breakaway walls are designed
local floodplain management and building code requirements. using the performance-based
design method, tall or large wall
• Breakaway wall sheathing and siding are discontinuous at the panels may result in wind loads
lowest horizontal structural member;horizontal separation joints that exceed flood loads. To meet
are provided to prevent damage to the sheathing or siding above the NFIP requirements, the wall
the lowest floor of the elevated building(see Figure 19).As shown geometry may need to be modified
in Figure 19, a watertight seal is provided for separation joints to reduce the tributary area for the
to prevent wind-driven rain and sea spray from entering the wind load. If this is not possible,
building envelope.A similar vertical sealed joint may be needed louvered or open lattice-work should
in front of the piling. be used in lieu of breakaway walls.
• Utilities,including electrical wiring, switches, outlets, breaker
boxes,power meters,plumbing, conduits, and ventilation ducts,
are not placed in or attached to breakaway wall panels. Building supply lines and other utility fixtures, such as
light switches or electrical outlets,may be attached to the sheltered side of vertical foundation members as allowed
by applicable building codes and floodplain management regulations(which generally require that utilities be
elevated above the PFE). If utility lines must be routed into or out of an enclosure, one or more of the walls are
constructed with a utility blockout(see Figure 14,Figure 15, and Figure 20). Utility lines that pass through the
blockout are independent of the walls to avoid being subject to damage if the wall panels break away.
• Breakaway wall panels are positioned such that, on failure,they do not collapse against cross-bracing or threaten
other foundation components(see Technical Bulletin 5).
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 47
• The configurations of partial-height breakaway wall systerns that are not permitted are not used(see Section 11.4 of
this Technical Bulletin).
• NVood-framed and steel stud-framed breakaway wall panels may be attached to pilings or other vertical foundation
members(i.e., all four sides of the panel may be attached) as accounted for in the design of the wall and foundation
elements.
• Masonry units are not attached to floor beams or to vertical foundation members with standard mortars.
• Continuous breakaway wall systems that span or overlap pilings or columns are not used.
11 Breakaway Walls and Other Building
Elements
Breakaway walls that form enclosures under elevated buildings can have direct impacts on the other building
elements, and some of the elements may impact the performance of breakaway walls.
11.1 Attendant Utilities and Equipment
Attendant utilities and equipment must not be mounted on, pass through,
or be located along breakaway walls. This Technical Bulletin describes the FREE-OF-OBSTRUCTION
proper placement of access holes (blockouts) to allow clear passage of utility CONSIDERATIONS
piping and wiring to minimize the possibility of impairing the performance of For more information On
breakaway walls(see Section 8.2 of this Technical Bulletin). building elements such
Only the minimum lighting circuits, switches, receptacles, and similar as elevator shafts, shear
elements that are required to be installed below the PFE to address life walls, utility chases, and
safety and electric code requirements should be installed, but they must not stairwell enclosures, see
be installed on breakaw w ay alls. These elem ents should be mounted on the Technical Bulletin 5.
sheltered or landward side of foundation members.
As discussed in Technical Bulletin 5, utility chases designed to protect utility
lines from weather are not considered enclosures for floodplain management or NFIP flood insurance purposes.
Utility chases must be small and sized such that they do not allow a person to enter the space (access panels for
servicing the lines are appropriate). Because a utility chase is not considered an enclosure, it does not have to meet
the enclosure requirements (breakaway walls/louvres/open latticework in Zone V and flood openings in Zone A).
However, the utility chase must still meet the requirement to be constructed of flood damage-resistant materials
below the PFE. Additionally, the portions of the utility systems below the PFE and the utility chase must be able
to withstand anticipated wind, flood, and debris impact loads (ASCE 7 provides the methodology for flood load
calculation) and must not be attached to, be mounted on, pass through, or be located along breakaway walls. Utility
lines within the chase must meet all of the NFIP requirements related to proper anchoring, resisting flood loads, and
preventing floodwater intrusion and accumulation.
48 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
11.2 Equipment (Tanks)
Tanks serving elevated buildings are covered in Technical Bulletin 5. Above-ground tanks must be mounted on a
platform supported on a foundation that is anchored to prevent flotation and lateral movement during a base
flood event or on a platform that is cantilevered from the building above the PFE. Tanks installed on the ground
are obstructions to the free passage of waves and water under elevated buildings. Tanks must not be mounted on
breakaway walls. Piping and wires must pass through utility blockouts and must not penetrate through breakaway
walls.
11.3 GaraDoors
Garage doors are subject to the NFIP requirements to break away under base flood conditions. Standard residential
garage doors may be considered breakaway panels, and flood loads acting on these doors need not be calculated
explicitly. Although garage doors have not been tested under wave loads, the I-Codes require the use of doors that
are rated for wind loads. Experience has shown that rated doors fail under low wave loading without significantly
affecting elevated homes and foundations. Designers must meet all wind load requirements for the building when
specifying garage doors. Garage doors and framing may be designed and detailed using the performance-based
design method provisions described in Section 10 of this Technical Bulletin. The performance-based design method
is required because the garage door frame does not match the layouts in the prescriptive or simplified design method.
11.4 Partial- i t Breakaway Wall Systems
A partial-height breakaway wall is a wall system in which only a portion of a wall panel is designed to break away and
a portion above the minimum required elevation is designed to remain in place (see Figure 24). Some configurations
of partial-height breakaway walls do not satisfy the NFIP requirements in 44 CFR§ 60.3(e)(5) and are therefore not
permitted. A partial-height breakaway wall configuration occurs when the bottom of the lowest horizontal structural
member of the lowest floor of the building is above the minimum required elevation. In the prohibited configuration
shown in Figure 24, a wall panel is split between a section that is above the minimum required elevation (below the
lowest horizontal structural member) and is not designed to break away while the other wall panel section is below the
minimum required elevation and is designed to break away. Any wall system below the lowest horizontal structural
member of the lowest floor must be designed to break away regardless of the minimum required elevation.
When the floor system of an elevated building consists of different floor levels, the structural member for the lowest
floor area is considered the lowest horizontal structural member. For example, if a house is constructed in Zone V
with Room 1 recessed 18 inches below the rest of the first floor, the lowest horizontal structural member of the lowest
floor(Room 1)is used to determine the maximum elevation that the breakaway walls would be required to extend up
to(see Figure 25). The configuration shown in Figure 25 is considered allowable.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 49
Figure 24: Prohibited partial-height
breakaway wall showing a breakaway �I!�,`'' '!' 'i'!�` '`�'
portion that extends only up to the
minimum required elevation and Lowest horizontal structural member----,,,_
permanent walls that extend from the / t .°'. ,f,s ..f/ °/ EL feet
Nnncampl��nt �� , `f,�''i Noncampilant �� �
top of the breakaway wall up to the Perrna nt wall d I I
lowest horizontal structural member
supporting the lowest floor. Example BFF „ri',}ii'i'iillNllslys51 `sli er !}i„`III ilt>?t,'o, tis sil ,,t1141
8.0 f,1,llllllllll 11 y�Ill llll i�l��llll!! {i't 1qs t{11„ltll l 3111 t 1��({�{r„ Timber it
```lll�CfllS p
elevations are provided for clarity. �,4\ `1IIIIIIIIIIIIIII „�lilll���\ 7��1
p y feet
Partial-height
breakaway
walls
I>��Il ,,,l�lllillll�ll,��IIIII�IIIII������� !rt vsbl ���� iiiiiiiiiiiiii{»�1��,l��1���11}7�1�'I,�'IIIIIIII k,�`'{�l
}lill��
�
1123i" Ill
(Slv}�101 l l?I��11p���I ��I�����11�ZN»
FL 2.0 fit u
Fran ible concrete slab Frangible concrete slab
W
Ground
I
Figure 25: Breakaway walls that
extend up to the lowest horizontal Room Room 2
structural member of the lowest Lowest horizontal
floor,which are considered full- structural member —'FL 1-1.5 feet
height breakaway walls.The section m Compliant
permanent wall
of the permanent wall above the —EL 10.0 feet r 'rll�Ir ,It,II111111111111 1 1't ;<#c,Qllll�lllll lf Il� ll�llll`I�IIIIII#il�i i,lt'}
right section of a breakaway wall is
compliant since the lowest horizontal
structural member of the lowest floor BFE
l�,illllli ilhil I(t��l�`��'1`l�l1 } 1111)��� IIs��S.t IE711 j11111hllli,i,i911h1+t`l��)�. �� '®'
for the buildingis located above the 8.4Il�ll
,h��l�y����1' I��� �}�1,}}117�1, 4t il ��Z, ��lll�;9, . t'! 1 iil�
feet ' t�';�,�� ll�ll��« 'r,�� 1,,1�� ,���� !,, �{ liill l�l�t� ll� I I��IIt "��( ,, Timber pile
breakaway wall in the left section. ��� �'��'1 �� I�1�'rr�i�sl�ll�!'�(1��� �.
��
Example elevations are provided for
clarity.
1111111 I��,�y 11111 �II ,x
h,,i,trill��l,l�l��ll,{»ll�l�l,!!!!I�� �Ilir iiiii�llllllllll���� �� ��,l�,l�tt,il4hllll,llll,llll��� L2.0feet
Frangible concrete slab Frangible concrete slab �<
I .j Ground
N I i
50 NEW TECHNICAL BULLETIN 9 SEPTEMBER 2021
Breakaway walls are not the only option. The space between the top of the breakaway wall and the lowest
horizontal structural member of the lowest floor could be open or covered with open lattice work or insect screening
(see Section 1.1 of this Technical Bulletin). Any wall section that is placed in the area below the lowest horizontal
structural member of the lowest floor must break away up to this elevation (see Figure 26). The configuration shown
in Figure 26 is an allowable partial-height breakaway wall provided it is designed using the performance-based design
method.
Breakawav walls are not required to extend to the ground or parking slab(see Figure 27). Since such a design conflicts
with the assumptions in the prescriptive and the simplified design methods, the design requires the performance-
based design method and a registered professional engineer or architect to demonstrate compliance with the
requirements that are described in this Technical Bulletin.
Figure 26: Breakaway walls that do
not extend up to the lowest horizontal
structural member of the lowest floor,
Lowest horizontal structural member which are allowable if the space
FL�t�. feet between the top of the breakaway wall
Allowable space
en space
lc and the lowest horizontal structural
open space open space
BFE member is open or covered with open
� {t °W ' lattice-work or insect screening and
ll'�� Timber pile
feet I',„# the performance-based design method
Exam is used. le elevations are
p
� Compliant
Will,
provided for clarity.
�3
breakaway
�ly� t��t iii����»lMt iii111111ih�tti1�1{ � it ,'yIy� ��� walls
IrtN11
£L 2.0 feet._
Frangible concrete sti, Frangible concrete slab A a
Ground
INFIX TECHNICAL BULLETIN 9 SEPTEMBER 2021 51
Figure 27: Breakaway walls that do not
extend to the bottom of the ground or
parking slab, which are allowable if
a registered professional engineer or Lowest horizontal structural member
architect verifies that the breakaway 's5J}�2'�l'}ii�ll IIlIII�}I}Il}llllllll I walls will break away during a base l`1l�1
,
Timber i[
flood event and the performance- gN
based design method is used. Example 8FE
8.0
elevations are provided for clarity. feet
Compliant
partial-height
�fet3kaLYay
walls
EL 3.55 feet
Allowable Allowable
open space open space
£L 2.0 feet
Frangible concrete slab Frangible concrete slab
Ground
9 9
and Multi-family Housing
Firewalls are required between townhomes, rowhomes, and multi-family housing units. 'lid-and high-rise structures
in Coastal High Hazard Areas may be allowed to use shear walls that function as firewalls (see Technical Bulletin
5). For low-rise buildings that require breakaway walls, special considerations in both firewall and breakaway wall
requirements must be satisfied. Design professionals should work with local officials and floodplain managers to
determine the most appropriate materials and detailing necessary to comply with fire safety requirements and meet
the intent of the breakawav wall requirements. When using a gypsum product is necessary, flood damage-resistant
non-paper-faced gypsum products that are compliant with NFIP Technical Bulletin 2, Flood Damage-Resistant
Materials Requirements, should be specified.
The NFIP does not require flood openings in breakaway walls in Zone V. ASCE 24 and some editions of the IRC
require flood openings in breakawav walls in Zone V and Coastal A Zones (see Section 3 of this Technical Bulletin).
Designers and local officials should determine whether flood opening requirements can be satisfied without flood
openings being placed in firewalls (see Technical Bulletin 1) or by using flood opening devices that are designed for
fire separation purposes.
11.6 Soffit r Elevated Buildings with Breakawayails
Coverings for soffits and the underside of the floor system of elevated buildings can be damaged when waves are
reflected up from breakawav walls that have not yet failed. When breakaway walls are subjected to waves,the walls on
the side of the building that is closest to the source of flooding typically fail first. The wave energy may be insufficient
to cause the breakaway walls on the landward side of the building to fail at the same time. In these situations,water
often runs up against the backside breakaway wall and splashes against the soffit covering under the floor system. The
water can damage or destroy the soffit covering and saturate the floor system.As a best practice to minimize potential
damage, more rigid soffit material should be used, and gaps and joints in the covering material should be sealed. The
soffits should be removed after a storm event to allow the floor system to properly dry.
52 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
11.7 Exterior Finishes
Exterior finishes such as brick veneer, concrete plank, stucco, and other unreinforced non-load-bearing elernents
may be attached to breakaway walls if the finishes do not inhibit the breakaway characteristics of the walls, which
can be accomplished by connecting the finishes only to the supporting breakaway wall panel and not across joints
between the walls and vertical foundation members. Designers should consider that these exterior finishes should be
designed/detailed to meet building code requirements for wind and seismic.loading. Horizontal separation joints must
be used at the top of the breakaway wall sections to minimize damage to the elevated structure when the wall fails
under flood loads. The separation joint must ensure that the exterior finish of the elevated building is not damaged or
compromised when the breakaway wall fails.
11.8 Interior Finishes
Enclosures below elevated buildings are allowed to be used solely for parking of vehicles, building access, or storage.
Installing utility stub-outs (i.e., purposely placed utility access points for future connections) is inconsistent with the
NFIP regulations for the allowable uses of an unfinished enclosure. Likewise, enclosures should be unfinished or, if
any interior finishes are used, the finishing materials must be flood damage-resistant(see Technical Bulletin 2). Other
materials may be used if required to address life safety and fire code requirements.
An exception exists for steel stud-framed breakaway walls when structural performance under wind loads requires
continuous lateral bracing of both stud flanges. When using a gypsum product is necessary, flood damage-resistant
non-paper-faced gypsum products compliant with Technical Bulletin 2 should be specified.
12 Construction Materials
The NFIP floodplain management regulations require that construction materials used below the PFE be resistant
to flood damage. Flood damage-resistant materials are those that are capable of withstanding direct and prolonged
contact with floodwater (i.e., at least 72 hours) without sustaining significant damage. Significant damage means
damage that requires more than cosmeticc repair,which allows for cleaning sanitizing and resurfacing. See Technical
Bulletin 2.
Unless other materials are required to address life safety and fire code requirements,flood damage-resistant materials
must be used for breakaway walls and wall panels, as described in the following subsections. See Section 11.8 of this
Technical Bulletin for an exception for interior finishes of steel stud-framed breakaway walls.
12.1 Wood Materials
Materials used in wood-framed breakaway walls must meet the following requirements.
• Standard dimensional lumber can be used because it is considered flood damage-resistant, but lumber is
preservative treated or decay resistant(e.g.,redwood, cedar, some oaks, bald cypress)if required by building code
provisions.
• Exterior siding is exterior grade and no thicker than 1/2-inch plywood,APA 32/16 rated sheathing, or other
equivalent sheathing material.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 53
• Wall studs are no larger than 2x4 inches(norninal dirnensions)unless designed using the performance-based design
method provisions described in this Technical Bulletin.
• Interior wall sheathing is not used in wood-framed breakaway walls.
12.2 Metal Connectors and Fasteners
Metal connectors and fasteners must be corrosion resistant (see NFIP Technical Bulletin 8, Corrosion Protection for
Metal Connectors and Fasteners in Coastal Areas).
12.3 Masonry Material
The following recommendations or requirements apply to materials used for unreinforced masonry materials in
breakaway walls using the prescriptive and simplified design methods:
• As indicated in Section 8.3 of this Technical Bulletin,masonry units must be 8-inch nominal units that conform to
ASTNI C90 with a compressive strength of 2,000 psi.
• Mortar for walls must be Type N conforming to ASTNI C270.
• Walls must be unreinforced including not having any horizontal joint reinforcement.
• Walls must be ungrouted cells.
• Any wood-framing materials used with masonry must comply with Section 12.1 of this Technical Bulletin.
12.4 Ot r Materials
All other materials that may be used to construct breakaway walls must be flood damage-resistant,including:
• Light-gauge steel framing, such as steel studs,must be coated to resist corrosion.
• Stucco, exterior insulation finishing system(EIFS)walls, and other lightweight exterior sheathing material may be
applied as long as a separation joint is provided where the material is attached at or near the bottom of the elevated
floor beam or joists to avoid damage to the building finish when walls break away(see Figure 19).
• Insulation must be installed with a separation joint at or near the bottom of the elevated floor beam so that it does
not hinder performance. Only sprayed polyurethane foam or closed-cell plasticc foams are identified as acceptable
in Technical Bulletin 2.
• Foam sheathed walls may be designed and used as breakaway walls in accordance with the performance-based
design method provisions in Section 10 of this Technical Bulletin.
Materials and products that are not listed in this Technical Bulletin may be used if reviewed and accepted by the local
official.
54 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
13 E A's tin g B uil din g s: R e p air s,
Remodeling, Additions, and
Retrofitting
Work that is determined to be Substantial Irnprovernent of an existing building (including additions and repair of
substantial damage) must comply with the NFIP regulations for new construction, and the entire structure must be
brought into compliance. Work on any building that was constructed in compliance with the NFIP requirements
that is determined to not be Substantial Improvement must comply with the requirements in place at the time of
construction and must not jeopardize the continued compliance of the building. Therefore, if enclosures are added
below compliant Substantially Improved buildings in Zone V, breakaway walls must be used. For more information
about the requirements for Substantially Improved and Substantially Damaged buildings, see FEMA P-758,
Substantial lmprovemeut/Substantial Damage Desk Reference(FEMA, 2010b).
14 Best Practices in Coastal A Zones
Mitigation Assessment Team (MAT) reports published by FEMA after numerous significant flood events have
consistently documented that buildings in areas mapped as Zone A and subject to tidal flooding, wave forces, scour,
and debris impacts are often severely damaged. The landward boundary of Zone V is where the depth of water can
no longer support a 3-foot breaking wave for the base flood. Zone A is mapped inland of Zone V (or the shoreline if
there is no Zone V)to the landward boundary of the SFHA.
In the portions of the SFHA that are mapped as Zone A, where the depth of flooding can support wave heights
between 3 and 1.5 feet (which only requires approximately 2 feet of water depth), there is more significant wave-
related damage than in the areas of the SFHA without waves. NFIP coastal Flood Insurance Studies since 2009 have
examined wave conditions in Zone A and mapped an informational laver on the Flood Insurance Rate Map (FIRM)
called the Limit of Moderate Wave Action (LiVIWA). The LiVIWA is delineated on FIR1VIs to indicate the inland
limit of the 1.5-foot breaking wave height during the base flood event.
The term"Coastal A Zone"is used to refer to areas seaward of the Li iVIWA and landward of the Zone V boundary or
landward of the shoreline where Zone V is not identified. Because of the increased risk of erosion, scour, and damage
from "moderate" waves in the Coastal A Zone, the I-Codes and referenced standards require higher construction
standards within these areas than in the rest of the Zone A(see Section 3 of this Technical Bulletin). However, Coastal
A Zones are not labeled on FIRMS, and the NFIP regulations for development in SFHAs and the NFIP regulations
that govern the identification of SFHAs on maps do not use the term"Coastal A Zone."
The NFIP floodplain management requirements regulate areas identified as Coastal A Zones to Zone A standards.
However, Coastal A Zones are subject to conditions similar to those in Zone V (Coastal High Hazard Areas),
including breaking waves, erosion, and scour. Because of the increased risks associated with moderate wave
action, FEMA strongly recommends that structures in Coastal A Zones be designed and constructed to meet the
requirements that apply in Zone V, including the requirements for breakaway walls. The NFIP Community Rating
System awards credits to communities that regulate Coastal A Zones to Zone V standards. Figure 28 shows a home in
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 55
3,
t4
� I
-l,• flf n k 4f i i N Ns s C! —a�'o-a� .l
11111011,
"
Figure 28: Home elevated above the BFE in Zone AE showing successful failure of breakaway walls.
Zone AE that was elevated above the PFE, and the breakaway walls failed as intended without darnaging the elevated
structure.
Because the Coastal A Zone is designated Zone A on FIRMS, the NFIP regulations (and I-Codes) require that flood
openings be provided in walls surrounding enclosures below elevated buildings (see Technical Bulletin 1). Breakaway
walls in Coastal A Zones must have flood openings that allow for the automaticc entry and exit of floodwater to
minimize damage caused by hydrostatic. loads. Openings also function to miuimize damage during flooding that is
shallower than base flood events or if anticipated wave loading does not occur with the base flood.
56 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021
15 References
This section lists the cited references cited in this bulletin. Additional resources related to NFIP requirernents are
provided in Technical Bulletin 0.
A NC (American Wood Council). 2018.National Design Specification(NDS)for Wood Construction.Available at lat)s:
Lm c_or,1
ASCE (American Society of Civil Engineers). 2010.ASCE 7-10,Minimum Design Loads for Buildings and Other
Structures.Available at hops «�-v«.asce.orQ .
ASCE. 2016. ASCE 7-16,Minimum Design Loads and Associated Criteria for Buildings and Other Structures.Available at
littp5 «-vv-vv.asce.orL,:/.
ASCE/SEI(American Society of Civil Engineers/ Structural Engineering Institute). 2005.ASCE/SEI 24-05,Flood
Resistant Design and Construction.Available at littps w\-4«.as(Le.or(y..
ASCE/SEI. 2014.ASCE/SEI 24-14,Flood Resistant Design and Construction.Available at hops -via«.asce.orQ .
FEMA. 2010a. FEMA P-499,Home Builder's Guide to Coastal Construction Technical Fact Sheet Series.Available at litt)s:
«w«.ti°ma.00v'emcroencv manaocrslrisk manaoement/huildino sciencelhurric apes#::text=FEMA P-499.
FEMA. 2010b. FEMA P-758,Substantiallmprovement/Substantial Damage Desk Reference.Available at https
oov cmerocncv-mangoers'risl�-mangoemcnt�huildino-sciencelmulti-hazard�:�aext=l7ocument FE\�I_y`%,20P-758.
FEMA. 2011. FEMA P-55, Coastal Construction Manual(Fourth Edition).Available at https \r\-v\a.icma.L):,o\ sites
defcult'files�2020 08 icma55 voli combined.pdf
FEMA. 2018a. FEMA 213,Answers to Questions About Substantially Damaged Improved/Damaged Buildings.Available at
https: \v-vv- r.icma. ov'emer encv mana c rs/risk-ma nagementlbuildin sciencelmulti hazard :next—FE\I��ti 213.
FEMA. 2018b. FEMA P-2023,Mitigation Assessment Team Report Hurricane Irma in Florida:Building Performance
Observations,Recommendations, and Technical Guidance.Available at hops �r�-v�a.icma.00� sites default 1?1es12020 071
mat report hurricane-irrna florida.pdi.
FEMA. 2019. Guidance for Flood Risk Analysis and Mapping:Coastal General Study Considerations.Available at htt_s:
www.icma�ovlsites default h1es12020-02 Coastal General Stuck- Considerations Guidance Nov 2019.1)df
FEMA.Various.NFIP Technical Bulletins. Current editions available at https: 1\.4\r\r-.f(,m c L):,ovlemcrg(,rre\--man cocrsl
risk manaoement/huildino science'national flood insurance technical bulletins.
• Technical Bulletin 0, User's Guide to Technical Bulletins.
• Technical Bulletin 1,Requirements for Flood Openings in Foundation Walls and Walls of Enclosures.
• Technical Bulletin 2,Flood Damage-Resistant Materials Requirements.
• Technical Bulletin 5,Free-o f Obstruction Requirements.
• Technical Bulletin 8, Corrosion Protection for Metal Connectors and Fasteners in Coastal Areas.
WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021 57
ICC(International Code Council). International Codes. Available at htths codesc csae.ol 'cat�gorvll Codes.
• 2012 International Building Code
• 2012 International Residential Code
• 2015 International Building Code
• 2015 International Residential Code
• 2018 International Building Code
• 2018 International Residential Code
• 2021 International Building Code
• 2021 International Residential Code
Tung, G.G.; B. Kasal; S.'XI. Rogers,Jr., and S.G.Yeh. 1999.Behavior o f Breakaway Wall Subjected to Wane Forces:
Analytical and Experimental Studies. Raleigh,NC: North Carolina Sea Grant,North Carolina State University.
58 WEIR TECHNICAL BULLETIN 9 SEPTEMBER 2021