Item H02AGENDA ITEM SUMMARY
Meeting Date: September 16, 2015 Department: Buildin
Bulk Item: Yes X No — Staff Contact Person/Phone 4: Christine Hurley, 289-2517
Ed Koconis 453-8727
AGENDA ITEM WORDING: Approval of resolution of the Monroe County Board of County
Commissioners adopting FEA Technical Bulletin 1 "Openings in Foundation Walls and Walls of
Enclosures" dated August 2008 as required pursuant to Monroe County Code Section 122-2(c)..
ITEM BACKGROUND Chapter 122 of the Monroe County Code "Floodplain Management"
includes rules for interpreting flood hazard issues. The building official shall be guided by the current
edition of FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and teclrnical bulletins
as adopted from time to time by the board of county commissioners. FEMA's Technical Bulletins
("bulletins") provide guidance concerning the building performance standards of the National Flood
Insurance Program (NFIP), which are contained in Title 44 of the U.S. Code of Federal Regulations..
The bulletins are intended for use primarily by State and local officials responsible for interpreting and
enforcing NFIP regulations and by members of the development community, such as design
professionals and builders. New bulletins, as well as updates to existing bulletins, are issued
periodically as needed. The bulletins do not create regulations, rather they provide specific guidance
for complying with the minimum requirements of existing NFIP regulations. Adopting these
documents as well as internal County policies would serve to allow the County to not only remain in
the NFIP as stated in Section 122-1(b), but also to rove forward with the intent of becoming eligible
to enter FEMA's Community Rating System (CRS). The proposed resolution would adopt FEMA
Technical Bulletin 1 "Openings in Foundation Walls and Walls of Enclosures" dated August 2008 as
required pursuant to Monroe County Code Section 122-2(c).
PREVIOUS RELEVANT BOCC ACTION:
January 18, 1994 — BOCC approved Ordinance No. 002-1994 adding the language "as adopted by
resolution from time to time by the Board of County Commissioners" to the rules for interpreting hood
hazard issues.
July 15, 2015 — BOCC rejected proposed ordinance amending Section 122-2(c) and directed staff to
continue proposing resolutions for adoption of both new and amended documents to be used by the
building official for guidance on floodpiain management.
STAFF RECOMMENDATION:
TOTAL COST: N/A INDIRECT COST: N/A BUDGETED: Yes No NIA
PREFERENCE:DIFFERENTIAL OF LOCAL
•ST TO COUNTY: N/A SOURCE OF FUNDS:
REVENUE PRODUCING: Yes _ No N/A AMOUNT PER MONTH N/A Year
APPROVED BY: County Atty X OMB/Purchasing Risk Management
DOCUMENTATION: Included X Not Required
DISPOSITION: ---AGENDA
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MONROE COUNTY,FLORIDA
MONROE COUNTYBOARD OF COUNTYCOMMISSIONERS
RESOLUTION i,
RESOLUTION OF ! 'iE COUNTY :#A'1 OF
COUNTYCOMMISSIONERS ADi
"OPENINGSBULLETIN 1 1 i 1
WALLS OF ENCLOSURES19 DATED AUGUST 2008
RE QUIRED. r MONROE COUNTYi1
SECTION
WHEREAS, Monroe County is currently a participating community in the National
Flood Insurance Program (NFIP') and is working on internal County policies to improve upon its
interpretation of NFIP regulations; and
WHEREAS, Monroe County desires to become eligible to enter FEMA's Community
Rating System (CRS); and
WHEREAS, Monroe County Code Section 122-2(c), in part, requires that in interpreting
other provisions of this chapter, the building official shall be guided by the current edition of
FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical bulletins as
adopted by resolution from time to time by the board of county commissioners;
i i i is �� i i� 1•.
Section 1. Pursuant to Monroe County Code Section 122-2(c), the Board hereby adopts
FEMA Technical Bulletin 1 "Openings in Foundation Falls and Walls of Enclosures" dated
August 2008, a copy of which is attached hereto.
Section 2. The Clerk of the Board is hereby directed to forward one (1) certified copy of
this Resolution to the Building Department.
PASSED AND ADOPTED by the Board of County Commissioners of Monroe County,
Florida, at a regular meeting held on the 16t" of September, 2015.
Mayor Danny L. Kolhage
Mayor pro tern Heather Carruthers
Commissioner Sylvia Murphy
Commissioner George Neugent
Commissioner David Dice
• '� i '
• i- � t
Mayor Danny L. Kolhage
(SEAL)
ATTEST: AMY HEAVILIN, CLERK
Deputy Clerk
W% WI, dywr � WIM M 0
� �^\��\\^����� \�\
Below Elevated Building,s in Special Flood Hazard' Areas
i
i n accordance with the National Flood Insurance Program
Technical Bulletin I / August 20iO8
'UtFEMA
VD S!�
[uzrodoctiou.............................. —........... ......... ............... ---... ....... —__.......... ...... --'l
NF1P&cguluUoms........................................ —...... ---........ ............... _................... ---./4
How Openings Affect Flood lmuovuuce Rates ..... .... --................................................ —_—'/&
DocoazeudncFElevations and Information &bmn|Openings ....... —...... —............... ........... 5
Enclosed Areas Below Elevated Buildings ............................ .......... _----............... —......... 5
Enclosures That Rcqtiire Openings..-----------------------_--.b
SiazadmmsThat. [)oNot RemaircOpenings -------------........ --_........... ]2
Reuuirconeamand Guidaucefor {onslIotionof Openings. ............................... —...... —....... 3
Minimum DJunubero[[)penin8o.............. —............ ---_—_--_----_......... 83
Height o[() /ogsAboveGradc-------_--___---------_----. 14
InstallationExamples............... ................ .... ...... ................ ---_—................ ... l5
Non -Engineered Openings and Engineered Openings ...................... ....... ---.................. —l8
[1/acceptu6lcMeoxurcy... _--... .......................... ------............................ —J9
Non-Emi ccrcdOpenings -------------------___--------2Q
£ imeered(}peuiogs-------------_----------_---------24
TheN FlP--........... —..... ...... ....................................... ........... --... ................. ............. -28
NFIPIecbucal 8n0etirm........... --............. _----............. ................
-------_'�2�
[)rdorngTechnicalBu0erbza--_---.................... .......... ---............ ---......
--_��20
Further InJCoconrion.................. ---....... ....... -------------........... --_..... 29
Glossary......................................... ------ ............ ...................................... ----_—...... 38
Comments omthe Technical Bulletins should bedirected to:
Department ofHomeland Security
FEKJAMitigation Directorate
5OQCStreet, SW.
Washington, O.C.2O472
Technical Bulletin 1-08 replaces Technical Bulletin 1-93, Openings in Foundation Walls.
Photograph Credits:
Figure 3.Bill Bryant, Anne Arundel County, Maryland
Figure 4. Smart Vent, Inc.
Figure17. North Carolina Emergency K&unmgememt/T Riddle
Protecting buildings that are constructed in special flood hazard areas (SFHAs) from dam-
aue caused by flood forces is an in-1POrtant objective of the National Flood Insurance Prograin
(NFTP). in support of' this objective, the NIFIP regulations include minimum building de-
sign criteria that apply to new construction, repair of substantially daniagcd buildings, and
substantial iniprovement, ot'existing buildings in SFH,;Vs. The base flood is used to delineate
SFHAs on Flood Insurance Rate 'Waps (FIRMs) prepared by the NF1P. The base flood is the
flood that has a 1-percent chance of being equaled or exceed-
ed in any given year (corrinioHly called the "100-year" flood).
C',ertain terms used in this Technical Bulletin are defined in
the Glossary.
The NFIP regulations require that residential buildings
I
constructed in A zones have the lowest floor (including base -
Merit) elevated to or above the base flood elevation (13FE). In
this Technical Bulletin, the term -A, zones" includes all zones
shown on FIRMs as Zones A, AE, Al-A30, NR, AO, and H.
Enclosed areas (enclosures) are pci-i-nitted under elevated
buildinus provided the enclosed areas meet certain use re-
strictions and construction YeClLti1_en1enLS related to flood
resistance, including use of flood damage-resistariL materials
and installation or openings to allow for allLoniatic entry and
exit of floodAvaters, Enclosures under buildings In V zones
(includes all Zones V, VE, and VI-V30) must meet the same en-
closure requirernen. ts except that openings are nou required
and walls must be non -supporting breakaway walls, open lat-
rice-work, or insect screening (see Technical Bulletin 9. Dev�5a,(rn
and Construr/ion Guidance fir BreakawaY Walls Below Elevated
Conshil BuddingO.
The NFIP regulations For neiv construction and substantial
ifl1provenients of existing buildings require that enclosed ar-
eas under elevated non-residential buildings meet the sarne
re-cluirenietiLs as those for enclosures tinder elevated residen-
tial buildings, New non-residential buildings constructed in A.
zones, and substantial improvements of' existing non-residen-
tial buildings, rinist either have their lowest floors elevated to
or above the ME or be floodproof'(-,,d (made watertight) to or
above the BFE.
Many types offoundations are used to elevate buildings, NVIlile
the main portions of' elevated buildings are above the BFE,
I
the foundation and any enclosed areas below the BFE will
be exposed to flood forces. Enclosed areas below the BFE
Under the NFIP, the "low-
est floor" is the floor of the
lowest enclosed area of
a building. An unfinished
or flood -resistant enclo-
sure that is used solely for
parking of vehicles, build-
ing access, or storage is
not the lowest floor, provid-
ed the enclosure is built in
compliance with applicable
requirements.
As used by the NFIP, an
:,enclosure" is an area that
is enclosed on all sides by
walls.
The NFIP defines a "base-
ment" as any area that is
below -grade on all sides.
The regulations do not allow
basements to extend below
the BFE.
Owners of existing elevated
buildings with enclosures
below the BFE may wish
to retrofit the enclosures.
Lower NFIP flood insur-
ance rates may apply if the
retrofit enclosures have
openings that meet the re-
quirements in this Technical
Bulletin and also meet other
requirements for enclosures
(limited use, flood dam-
age -resistant materials, and
elevated utilities).
TECHNICAL BULLETIN I - AUGUST 2008 1
(including crawlspaces) are permitted if used only for parking of vehicles, building access,
and storage. R-Ure I illustrates a Liy ical crawlspace foundation wall and a typical framed wall
1 Z7) 1 p p
surrounding an enclosed area.
I
If enclosure walls are not clesigned with openings to relieve the
pressure of standing or slow -moving water against them (called
1 0
hydrostatic loads), the walls can be daniaaed or Fail durino, a,
flood. If the walls are "load -hearing" walls that support the el-
evated building, failure of the walls may result in damage to,
or collapse of. the building. To address this concern, the NFIP
regulations require that enclosure walls contain openings that
will allow for the automatic entry and exit of floodwaters. These
openings allow floodwaters to reach equal levels on both sides
of the walls, therebv lesseninIg the potential for damage caused
by a difference in WrosLan c loads on opposite sides of the
walls. In A zones, the requirerrient for flood openings applies
C,
to all enclosed areas below new elevated buildings and below
I
substantially improved buildings.
Areas of shallow flood-
ing may be shown as AO
zones on FIRMS. Rather
than BFEs, AO zones have
"flood depths" that range
from 1 to 3 feet. In these
zones, all NFIP require-
ments related to BFEs
apply, including elevation of
the lowest floor to or above
the designated flood depth
and requirements for enclo-
sures with flood openings
that are located so that
floodwaters will flow in and
out.
This Technical Bulletin explains the NFIP requiren'ients for flood openings and provides
P
guidance for prescriptive (non -engineered) openings and engineered openings. Nori-eup-
n "n
neered openings are used to meet the NFIP's prescriptive requirement off square inch of net
open area for every square [bor, of enclosed area.. 1,ks an alternative, erigincered openings that
7)
have characteristics that differ from non -engineered openings niav be used provided them are
0
desit"Yned and certified by a registered design professional as meeLI'My certain Performance
characteristics described in this Technical Bulletin.
IN Joist/Truss
Solid perimeter
(I—Crawispace
foundation wall
(CMU or poured
concrete)
Flood opening
No more than
1 foot
Interior grade
Exterior grade
—Footing depth per
building code
Figure 1. Typical enclosures with flood openings
Flood opening
No more than t Interior grade
1 toot
Exterior grade
This Technical Bulletin also diSCLISSCS how openings Could affect flood insurance premiLlInS,
provides examples of enclosures that require openings and situations where openings are not
required, and outlines the requirements for, and provides UlLidance on, the following:
11 In
E Installation of openings including the minimurn number of openings and heigl-at of open-
ings above grade,
0 Non -engineered openings, and
I
0 Engineered openings,
Examples are provided to illustrate types of buildings and enclosures that require openings,
and to address several corrimonIA, encountered situations. Other- situations may require the ad-
wice a registered design professional. Questions should be directed to the appropriate local
0
official, NFIP State Coordinating Office, or FEED Regional Office.
Solid perimeter foundaLion walls and walls surrounding en-
closed areas below the BFE may be damaged by forces related
to moving floodwaters and wave impacts (called hvdrodynarnic
loads), and debris impacts. The requirement for openings is
intended t« reduce only flood damage associated with hydro-
SLILIC - not hydrodynamic - loads.
Hydrodynamic loads and debt -is impacts may be significant. in
s0ule flood hazard areas shown as A zones on FIRMS, includ-
ing riverine areas where high flow velocities are likelv (e-g.,
faster than 5 feet per second) and areas where wave heights of
1.5 feet or more are possible- In these areas, it is recommend-
ed that a registered design professional evaluate foundation
designs. ()pen foundations without enclosed areas are less vul-
In
nerable to the r),j-)e of damage that can be caused by high flow
velocities and wa-ve action.
This Technical Bulletin dis-
cusses openings in walls
below the BFE. Readers
should check with the
community to determine
whether a higher eleva-
tion standard is enforced.
For example, communi-
ties may add freeboard or
may regulate to the design
flood elevation (DIFE). In
those cases, references to
the BFE in this Technical
Bulletin should be con-
strued as references to
the community's elevation
requirement.
Buildings in V zones (Zones V, NTE, and VIA'30) MUSL MCCL certain design and construction
requirements that are specified in the NFIP regulations at Section 60. 3 (e). The area below the
lowest floors of buildings in N' zones must be free of obstruction or, if enclosed, the walls of
enclosures must be constructed WILh non -supporting breakawav walls, open wood lattice-,vork,
or insect screening. Openings may be provided, but are not required, in hreakawav walls Lin-
der buildings in V zones. For information on V-zone design and construction requirenwins,
refer to the NFTP regulations, the Technical Bulletin series (especially Technical Bulletin
5, E)ee-(af-Obstruclion RetyltiMMPTILY and Technical Bulletin 9, and. Construr6on Guidance
fir Breakaztla - i) Malls Below Elevated Coastal Bllddbig�), the Coastal Consh-uction AIaE.\Lk nual (F
55CD), blood Resistant Dev'gw and Construction (ASCE 24), and Home Builders Guide to Coastal
(:'onstruclion (FETNIA 499).
TECHNICAL BULLETIN 1 - AUGUST 2008 3)
The NFIP regulations for enclosures are codified in Title 44 of the Code of Federal Regula-
tions, in. Section 60.3 (c) (,5)), which states that a corrimunitvshall:
"Require, for all new co'nstruction and sahstanlial anprovements, tha(fidly enclosed ar-
eas below; the lowest floor that are usable solely for Parkincr of vehicles, bvtilding access,
or Vame in an, area other than a base anent and which are subjecl lo'flooding shall be
designed to autoinatit'ally, equalize la3drostcr.lac f2crorl lcarces on exterior walls ky allowing,
jbr [he entry and exit qffloodwaters, De5ig-nsfor meeh'n.g this requirewerd nia-st either be
Certified lay - a regislered Piqf�sslonal engineer orarrhilert or viect or exceed (he fiWowing
atinimum crderiti: A raaaaai. aaacrn of't-wo openings having a total net area ofnol, less than.
one square inch for eery square jbot of'enclosed area sul>jecl to./loodlingshall be provided.
,The bottom qf"all olmnings shall be no higher than. ovefiot above grade. Opening:s may
be equiJ51)ed with screens, louvers, valv(r�s, or other f.,overingv or dem"Ces Provided that these
Perinit the automatic entry and exit (Y"f/00(171)(11M.
Prol)(.,)sals for SUI)SM11tial improvement Of CXIS1111- bUild'1110-S in SFHAs', and proposals to repair
those that have Sustained substantial damage, niust complv with the requirements for new
construction. In A zones, the applicable requirements IFICILLdc openings in the walls Surround-
ing enclosed areas belm,v the BFE. As part of issuing permits, community officials must review
such proposals to determine whether they cornpl\Y with the requirements. Further informa-
tion on substantial improvement and substantial damage is found in Answers to Questions ;41)out
Subslantiall) Damaged Buildings (FEALA, 213).
The NFIP Technical Bulletins provide guidance on the minimum requirements of the NFIP regulations.
Community or State requirements that exceed those of the NFIP take precedence. Design profes-
sionals should contact the community to determine whether more restrictive provisions apply to the
building or site in question. All other applicable requirements of the State or local building codes must
also be met for buildings in flood hazard areas.
Careful attention to cornpliance with the NFIP regulations f-or flood openings is important
during; design, plan reviews, construction, and inspection. Compliance influences both the
I
svul tie rabi lity to flO0d &t1flage and the cost of NFTP flood insurance. if -openings are not cony-
pliant, the floor of the crasVispace or the floor of'Llic enclosure becomes the "lowest floor." In
those cases, the result may be significantly 1-60-her flood insurance premiums, especially if -the
floor of the crawlspace or enclosure is more than a foot or two MOW the BFE,
4 TECHNICAL BULLETIN I — AUGUST 2008
Coniniunities are required to collect data frorn pern-iiLrecs to dc,CUnicni the sturveved elevation
of the lowest. floors ofnew buildings and existing buildings that are substantially improved.
although the data may be provided in other fort-riats, the NFTP's Elevation Certificate (FENTIA
Form 81-3 1) is designed specifically for this purpose. The current version ofthe Elevation Cer-
tificate is online at litt.p://i�\N-ikfetyia.go:vl.,"bitsiness/'nFip,"elvinsi.sht-m,
The Elevation Certificate is designed to collect information that facilitates deLernii.nin g com-
pliance of new coristruction and to provide data necessary for -the proper rating of'NFIP flood
insurance. For guidance, see the hisn-UCtiOnS that accompany the Elevation Certificate and
the. (FE R Floodf&zin- Nfanaaemenl uen: F-Jevalion ertM, (FEN[, 467-1
11� lltiC01,ca
The Elevation Certificate has blanks that are to be cornpleted if"Ll-tere are enclosures under
elevated buildings, including:
• The square footage of the enclosed area,
0
• The nuniber of flood openings Nsqithin LO foot above adjacent grade, and
• The total net area of flood openings.
The Elevation Certificate provides space for comments. As noted above and explained in more
detail below, the regulations provide owo) ways to satistV the requiretrien ts fear- openings.
'71
inerus should be provided when engineered openings are used, and when there are Other
aspects of enclosures and openings that comply with the reqUirernents but that, Without CIOSe
inspection, may- appear to be non -compliant.. The clocturientation required for engineered
n
openings should be attached to the Elevation Ccrtificate (described on page 25, Docunictita-
tion of engineered openings foi- flood insurance).
l I
1� �
III 11�11r;1111��11
U 1A a 1; ig=
The RP re12_UJaLiOuS specify that, enclosed areas under elevated buildings inav be allowed
provided the enclosed areas are used solely for:
0 Parking of''vehicles (attached garages or parking areas be-
low elevated buildings)
E Building access (staMvcIls, Fovers, elevators)
N Storage (low -value items)
Although crawlspaces are not listed explicitly as an allowable
use, buildings niay be elevated USirla perimeter foundation
In
walls that create enclosed areas, UVPiCalIV called crawlspac.es or
under -floor spaces. Crawlspaces provide access to under -floor
utilities such as pipes, CIUCLwork, arid electric conduits.
Some communities require
permittees to execute a
"non -conversion" agreement
to document their under-
standing that the use of
enclosures is limited, that
conversion to other uses is
not allowed, and that modi-
fication of enclosures may
result in higher NFIP flood
insurance rates.
It is important to understand how an otherwise cornpliant en-
closed area below the BFE can be rendered non-cornpliant by
installing Features that are not consistent with the limitations
On uses. The following are not allowed below the BFE because
of potential damage and their presence is inconsistent with
the allowed uses: appliances, heating and cooling equipment,
plumbing fixtures, more than the minimum electric service
required to address life safety and electric code requirernents
for building access and storage areas, and materials that are
not flood clam age -resistant.
The only exception to the
openings requirement is
for non-residential build-
ings that are engineered to
be floodproofed by meeting
stringent requirements to
be watertight. For informa-
tion on floodproofing, refer
to Technical Bulletin 3, Non -
Residential Floodproofing
— Requirements and
Certification.
The NTFIP regulations require that enclosed areas surrounded
by solid walls that extend below the BFE have flood open-
ings. The requirement applies whether the walls are load -bearing Nvalls or non -load -bearing
walls. Therefore, openings are required in solid peritneter Foundation walls that SUITOUnd
crawlspaces and openings are required in the walls of fuilly enclosed areas that meet the use.
lirnitations (parking of vehicles, building access, or storage). The requirement applies to new
construction and to buildings that are undergoing substantial 11upl-OVCHICut, ir]Cltldin1,�)� repair
of'substantial darnag.,e.
Several examples of enclosures that require openings are described t)(Jow
E Solid per-Inleter foundation walls (crawlspaces or under -floor spaces)
IN Solid perimeter foundation walls (bclmv-u-T-ade crawlspaces)
0 Solid perimeter foundation walls (with full -height Under -floor spaces)
• Garages attached to elevated buildings
• Enclosed areas under- buildings elevated on open I'Ouridations. in A zones
• Enclosed areas with breakaway walls under buildings elevated on open f-oundations in A
zones
• Solid perimeter foundation walls on which rnar1UfaCttlr_Cd 11011-ICS are installed
• Accessory struCH-11-CS (detached garages and storage sheds)
"I i 1 1 - =F iYalis tGIMMIaGes or MOM-79
ipaces)
The crawlspace or underfloor space that is created when a
building is elevated on a solid perimeter Foundation Nvall is an.
enclosed area below the BFE that must meet all of the require-
inents for enclosed areas (refer to Figure I ). If a brick veneer,
siding, or other material covers the wall, then the openings
must coin pletely penetrate into the enclosed area. Acrawlspace
access with a door does not qualify as a flood opening unless
In many parts of the coun-
try, a common practice is
to build "conditioned crawl -
spaces" that are sealed and
have mechanical ventilation.
In SFHAs, all crawlspaces
must have flood openings
that meet the requirements
of the NFIP and the building
codes.
the door has an opening installed in it or otherivise meets the. performance requirement that
it will allow autoniatic entry- and exit of floodwaters.
As explained on page 14 (Height of Openings Above Grade), the hottorn of each opening is
to he located no higher than I foot above the higher of the final interior or. exterior grades
under the opening. Therefore; placement of the openings in the foundation wall requires
knosa-leclge of the expected finished exterior grade and the final interior grade, of the cra�swl-
spac e.
Building code requirearients rnav call forventilzation of certain under -floor spaces. Ventilation
openings typically are positioned near the top of the foundation wall to facilitate air flow. In
most cases, ventilation openings wrill be too high above grade to statisA- the requirements for
flood openings.
The NF1P regulations do not callow buildings to he constructed
with areas that are below grade on all sides (basements), cx- Communities sles are required
#o adopt specific provi-
cept for certain engineered non-residential Buildings that ai-e signs in their ordinances
designed and certified to he floodproof d. Therefore, crawl- to be consistent with the
spaces that are below -grade on all sides are not allowed because limitations in TB 11 in or -
they are basements. An exception is available only in shallow der to permit below -grade
floodplains, and then only if certain other requirements and crawlspaces.
limitations are rnet. Those requirements and hmittations are
detailed in Technical Bulletin 11, C:rawlsjmcr C onsiruclion fbr• Building„ Located i.ri. Special l;tood
Hazard .4a~ras: National Flood h7-
slitr(IIraccI I''xogrcrw Interim Guidance.
According to this guidance, he -
low -grade crraivispaces niav b
allowed provided the wall height
is less than 4 feet when measured
from hottorn of the flooe` ,joist,"
truss; to the top of footing, which
must be no more than 9 feet be-
low -grade (,see Figure. 2). Flood
openings are required in the
foundation walls surrounding
these crawlspaces and, as noted
above, air veritiladon ana-v be re-
quired.
:-although crawlspaces that stitisfy
the limitations in TB I are not
considered haseirients for flood -
plain rnana ercacrit purposes, it
is important to note that. they
are baserncnts for NF1P flood
JolsttTruss
BFE —�-
Flood opening
No more than
1 foot 4-foot
maximum
Exterior grade mtoot
maximum
Interior grade
Figure 2. Limitations on below -grade crawlsaces in shallow
floodhazard areas JB 11)
TECHNICAL BULLETIN I - AUGUST 2008 7
insurance poses. Therefore, NFIP flood insuranceivill be more expensive if the grade inside
the crawlspace is below the exterior grade on all sides. In addition, below -grade crawlspaces
I
rnav coricrihute to increased hurnidity and mold growth. TB 11 requires that an adequate
drainage syscen-i be provided in order to minimize floodwater contact `hill crawlspace 11-lateri-
als and related moisture damage.
In SFFUVs where the BFE is more than 4 or 5 feet above grade, or where owners want enough
I
head room to allow for parking of vehicles and storage, solid perimeter foundation walls may
be used to create full -height under -floor spaces (see Figure 3). The walls surrounding the Lin-
der -floor space must meet all of the opening requirements.
It is important that full -height under -floor spaces also meet all other NFIP requirements to
minimize the likelihood of' future CORVCF.SiOn to uses other than the allowed uses (parking
of vehicles, building access. or storage). As noted in the discussion of limitations on uses of
0 storage).
enclosures, the l"OHOW111- are riot alloNved below the BFE in full -height enclosures because of
potential dania-c and their presence is inconsistent with the allowed uses: appliances, heating
I..) 1�
alid cooling equipment, plumbing fixtures, more than the minimum electric service required
to address life safety' and electric code requirements for building access and storage areas, and
materials that are not flood damage -resistant.
Figure 3. Full -height
solid perimeter walls
surrounding garage and
storage area (only two
openings visible)
Et �
Many buildings, especially homes, are, designed with attached garages, An attached garage
inav have its floor below the BFE provided the garage meets all of the requirements for an ell -
closed area below the BFE. The use of the garage space unList be limited to parking of vehicles,
building access, and storage.
TECHNICAL BULLETIN I - AUGUST 2008
Openings are required in the exterior walls of the garage, and openings may be installed in
exit doors and garage doors (see Figure 4). It is important to note that garage doors them-
selves do not meet the requirements for openings. Hun-ian inten.Ten(ion would be necessary
to open garage doors when flooding is expected, which is inconsistent with the requirement
I
that openings allow for the automatic entry and exit of floodwaters. Similarly, gaps that may
he present between the garage door and the door.jamb or walls do not guarantee automatic
entry and exit of floodwaters and do not count towards the net open area requirement.
if an attached garage is built with its floor below the BFE and it does not have compliant
openings, the garage [loot- becornes the lowest floor. Flood insurance premiums may, be sig-
nificantly higher than if the garage complies with the requirements for openings and other
requirements, such as flood damage -resistant materials, and elevated utilities.
Figure 4. Attached
garage, with engineered
openings installed in the
garage door
* building that is elevated on an open foundation (e.g., piers, posts, columns, or pilings) in an
* zone may have enclosed areas below the elevated floor (see Figure 5) . Sometimes only part
of the footprint is enclosed, such as for a stairwell or storage roon-1. All of the requirements for
enclosed areas apply, including openings, elevated utilities, flood damage-resisLariL materials,
and lirniLations on use (parking of vehicles bUildit](T access
and storage)
Open foundations are recommended in riverine flood haz-
ard areas where flow velocities are expected to exceed 5 feet
per second because of the anticipated hydrodynamic loads
and potential for debris impact and scour. These loads may
be sufficient to damage typical solid perimeter foundation
walls, even though flood openings are provided,
ASCE 24 and several of
the fact sheets included in
the Home Builder's Guide
to Coastal Construction
(FEMA 499) are excellent
resources for flood -resistant
building methods in coastal
A hazard areas.
TECHNICAL BULLETIN 1 - AUGUST 2008 9
If a waterway was studied rasing detailed methods and a floodwav is shown on a FIRM, then
the Floodww-ay Data Table in the Flood. Insurance `study should be reviewed for data that can
be used to estimate velocities. For each cross section, the table provides the mean velocity that
can be used tow approximate velocities in the floodplain outside of the floodway. For other wwa-
terwvays in areas known to have fast-moving water, standard niethods can be used to coaaapute
an approximate velocity. Examples of other sources of infortnation that should be reviewed
include local observations and studies prepared by State and local agencies.
Figure 5. Enclosure with flood
openings, under house elevated on
pipings
� • � � ^ . rw ;; ' . . , � • � � ' a! • ra i art - r ak � >f
Open foundations are also reco nanended in A zones in coastal areas where breaking weave
heights can be between 1.5 and 3.0 Ceet (called Coastal A lanes). In these areas, it is recom-
naended that walls surroun din- enclosed areas be desi-ned as breakawwat wwall s. Flood ctpctlir�t�4
are reouired in breakatww=aav walls in A zones in circler tca c'<7lrFAV with the NFIP renuirements.
.CSC C 24 includes specific provisions for openings in breakaway walls.
�Tanufa ctrrre.d harries rnav be installed on solid pc.rune:Let- foun-
dation walls that enclose space below the. homes (sere Fig -tire 6).
E e n if it is not pall of the load -bearing f0undation a solid
perimeter wall is required to have openings, otherwise hydro-
static loads ntay dainaage the perimeter wall, which could, in
turn, datna e the: home's supporting foundation and anchor
syste°tn.
Figure I showers an exarnple of a f -a:rned enclosure below an ele-
vated nzant.rfacttn�ecl Borne. In this case, the full -height enclosed
Openings are required in
rigid skirting that is attached
to frames or foundations of
manufactured homes to re-
lieve hydrostatic loads and
minimize transferring loads
that can damage homes
and their supporting foun-
dation systems.
10 TECHNICAL BULLETIN 1 - AUGUST 200
area is used for parking and storac-c. Openings are required because the W111S SUFFOUriding
tile enclosed area are solid walls. As indicated by the driveway on the left, the interior slab is
higher than the exterior grade along the side of the building. The openings shall be located
within I foot of the interior grade.
Figure 6. Manufactured home
supported on piers; masonry perimeter
wall with flood openings (ground
anchors not shown)
Figure 7. Manufactured
home installed above
a full -height framed
garage (note elevation
of driveway slab on left;
the openings are within
I foot of interior grade of
the slab)
TECHNICAL BULLETIN 1 - AUGUST 2008
I
Detached garages "n may
arages and detached storage buildings in A zones mbe permitted without requir-
in them to be elevated if they comply with all of the requirements for enclosures. Garaces
and 001C.1- accessory buildings ruLlSt be used onlg y for parkinof vehicles and SLOrage, utilities
1.) i 11�
must be elevated, flood damage -resistant materials must be used below the BFE, the require-
Irients for flood openings Ilikist be satisfied, and they must be anchored to resist flotation,
collapse, or lateral inoverrient under flood conditions.
C011-lunini ties are required to regulate all development in SFHA-s, including the placement of
small storage sheds. Storage sheds in ik zones are not required to be elevated if they comply
with all of the requirements for enclosures. They must be used only for storage, utilities MUSL
be elevated, flood clarnage-resistant materials must be used below the BFE, and the require-
ments for flood openings inust, be satisfied. In addition, sheds are to be anchored to prevent
flotation, collapse, or lateral movcirient under flood conditions.
Situations That Do Not Require Openings
Two situations that do not require openings are described below:
• Ntanufact.ured home with skirting
• Back -filled stein wall foundation
ARIMMI VV I I i Wiff HT , 411TATH-T—W11111=1 R
,Skirting used to enclose the area under inailUffiCtUl-ed 1101nes
typically is made of weather -resistant material and extends
I
frorn the bottom of the home down to gracle. Flexible skirt-
ing and rigid skirting that are not attached to the frame or
f'oundation of a manufactured home are not required to
have openings. However, w,vhere floodwaters are expected to
11�
rise rapidly, there may be concerns ab011t, tile skirting being
pushed against fOL111dation systcrris, In these areas, open lat-
tice may be more appropriate to rninirnize the POLelulal for
flood dainage.
A filled stein wall foundation (also, called a chain wall) can
look like a Solid PCrilllCtCY foundation wall froin the outside,
The National Fire Protection
Association's standard,
Model Manufactured Home
Installation Standard (NFPA
225), specifies that instal-
lation of skirting does not
trigger the requirement for
flood openings provided
the skirting does not pro-
vide structural support and
will collapse under wind and
water loads that are less
than those expected during
the base flood event without
causing structural damage
to the elevated home or the
foundation.
but this type of foundation is backfilled With compacted struc-
tural fill that supports the floor slab (see Figure 8). Because of the rill, Unbalanced lateral
loads against the walls will be minimized as floodwaters, and thus openings are not required.
Ij
It is important that the final Elevation Certificate, or other dOCLInlentation of elevations, in-
clude ari eXplallat-101-1 when stern wall fc)Undatioris are used to avoid the assumption that it
is a crawlSpaCC that lacks the required openings. The Elevation Certificate diagrams do not
illustrate filled stern wall foundations.: note in the comment section should describe the
foundation so that insurance ageriLs, are alerted as to why there are no openings.
12 TECHNICAL BULLETIN 1. - AUGUST 2008
Figure 8. Back -filled stem wall
foundation (openings not required)
The NFIP regulaLions specify certain installation requirerricrus that MUSL be niet by all flood
openings, whether non-enIgineered openings or engineered openings, which are described
starting On page 18. The installation requiretrients address the minimum number of openings
I
and the inaximurn height ofopenings above gracle. Additional guiclance and explanations for
Val-10LIS Situation$ are, described below.
Each enclosed area is required to have a 111111iHIL111-1 Of tti�To openings on exterior walls to allow
floodwaters to enter- directly. In order to meet the requirerneriL, the openings must be located
so that the portion of the opening intended to allow for inflow and Outflow is below the BFE.
Openings that are entirely above the BFE (or any portion of an opening thatisabove the BFE)
will not. serve the intended purpose during; base flood conditions and thus are not Counted
towards the compliance with the flood opening requirernents.
The openings should be inscalled on at least two sides of each
ope
nings -
enclosed area to decrease the chances that all openings could
be blocked with floating debris and to allow for niore even
filling by floodwater and draining OF the enclosed aFCa- It is
recorntrietided that openings be reasonably distributed around
the perimeter of the enclosed area unless there is clearjustirl-
caLion for putting all openings on just one or two sides (Such
as in townhouses or buildings Set into S10l)iu1c1 Sites).
D
The International
Residential CodeO and the
International Building CodeO
(by reference to ASCE 24)
both require a "minimum
of two openings on differ-
ent sides of each enclosed
area."
TECHNICAL BULLETIN 1 - AUGUST 20078 13
Figure 9 shows a sketch illustrating where openings could be located when an elevated build-
ing has multiple enclosed areas. [Note: the nuaiber of openings shown in Figure 9 is for
illustration only; the total riumber of openings and the adequacy of the net open area of those
opernnZ-, depend on the type of opening, covering, and whether vent devices or engineered
openings are installed.]
installed in garage door
Figure 9. Sketch of foundation plan of home with multiple enclosed areas, each with flood openings
(number of openings for illustration purposes only)
The bottom of each opening is to he located no higher than I foot above the grade that is
inimediatCIV under each opening. The purpose of this rcquireirient, is to satis.ft, the perfor-
mance expectation that the difference in water levels between the interior- and exterior will
not exceed I foot as water begins to rise and as floodwaters recede from the site. Note that the
openings (or those portions that count towards the required net open area) must be located
Wow the BFE. In areas with shallow flood depths, this inay- require positioning the openings
0
closer to grade than the tnaxinimn I foot allowed.
Given the requirement that the bottom Of Openings shall not be higher than I foot above
grade, a question arises if the interior and exterior grades are different: which grade should
be used to determine placement of flood openings:' The higher of the final interior grade
and the finished exterior grade that is immediately under each opening is used to make this
determination:
0 Finished exterior grade. ('are should be taken when placing backfill, topsoil, and land-
scaping materials arOU.nd the OLItSide Of enclosures, especially solid perimeter -foundation
Z7) 2
1.4 TECHNICAL BULLETIN 1 - AUGUST 2008
walls. If the finished exterior o-rade is hi -her than the interior grade on all sides of the
building, then the enclosed area becomes a basernent as defined by the NFTR
0 Final interior grade. The trench that is excavated to construct footings and foiindarion
t,valls must be backfilled completely, otherwise a basement is created. If the interior grade
is higher than the exterior grade, the openings are to be no higher than 1-FooL above the
interior grade.
MMIF-Urs MiMMMIM
MM=
Consider a crawlspace enclosure that has its interior grade higher- than the exterior grade. As
water rises against the outside of [lie fonridation, the grotind or fill on the interior balances
the hvdi-ostatic load (see only 10). It is on Figure Fig when the water rises above the interior grade
U I
than the lateral load becomes iinbalanced and therefore rritist. be eqtialized by openings.
U'lien -,Iewed from the oLasicle, a solid perimeter foundation wall or wall surrounding an en-
closed area with the interior grade higher than the exterior grade will appear to not meet the
installation reqLtircirierits for openings. The openings will appear to be too high above [lie ex-
terior grade (illustrated in Figure 7). Therefore, it is important that the final documentation
0 111)
of aS-bLI111 CICAratiOnS note the difference in interior and exterior grades. For example, if the
NFIP Elevation , ertificaLe is used, coininems should explain that the interior grade is higher
than the exterior grade and it should be noted whether the openings are (or are nor) within
I ft)ot of the hi -her ot'the two grades.
Figure 10. Illustration of flood
openings installed within 1 foot of the
higher of interior or exterior grade
TECHNICAL BULLETIN I - AUGUST 2008 1.5
MIM t=
Buildings on solid perimeter foundarion walls that are :set into a sloping site present another
special situation with respect to installation of'openincys. Careful attention nitiSL be paid to the
following:
N The interior floor along the lower side of building that is Set Into a Sloping Site must be
at or above the exterior grade across the entire length of that side of the building, odier-
In 11.)
w,vise the enclosure becomes a basenient.
0 The bottom of each opening shall be located no higher than I foot above the exterior or -
interior grade 11-11mediately below the opening, whichever is higher (see Figure 11).
M For openings to perforin their intended function, sufficient open area must be below the
BFE.
Figurell. Openings in enclosure
walls, sloping site
BFE tBFE
Each opening
no more than
1 foot above grade
Interior grade must be at or
above the exterior grade along
the entire length of the lowest
side to prevent being a basement
Town h ouses are single-Fairilly dwelling units constructed in a group ofthree or more attached
units in which each unit extends froul foundation to roof and with exterior walls on at least
two sides, Openings are reqUil"Cd if townhouses in SFRAs are constructed with solid perimeter
foundation walls or with solid walls surrounding enclosed areas tinder the elevated portion of
the building'
Because the interior toNvnhouse units have less linear exterior- wall length than the end units,
it can be a challenge to meet all of the requirements, especially the requirernent for adequate
net open area and the requirement that each enclosed area have openings If openings call -
not be provided in at. least two walls, the NFlP allows all. openings to be installed in one wall,
TECHNICAL BULLETIN I - AUGUST 2008
Desigri Of interior tOWL-111OLIse units can satisfy the uttidance that openings should be on differ-
ent sides if the walls inside the enclosed area have openings to connect enclosed spaces from
front to back. Figure 12 shows stiggesied locations for openings, [Note: the number of'open-
ings sho-�vn. in Fi-ALVC 12 is for ilh,istration onh; the total number of openings and the adequacy
of the net open area depend on the type of opening, covering, and wheffier a vent device is
installed in the openings.]
It may be even more challenging to provide adequate openings in enclosures tinder interior -
townhouse units if the nitilt.1-unit building, is set into a sloping site, in which case it may be ap-
propriate to consider iisin'(; a filled stem wall foi,iridabon or an open foundation. Use of fill
I
across one side of elevated townhouses may create a similar complication.
Figure 12. Illustration of suggested flood openings in enclosures under elevated townhouses (number of
openings for illustration purposes only)
NOMMMMI Mj oRMUMM-MV
Only those portions of openings that are below the BFE can be counted towards the required
net open area. Stacked vent devices may be installed or large -dimension openings may be pro-
vided (Figure 13). In both cases, if the BFE does not reach the top of the opening, only the
portion that is below the BITE will COLInt as contributing to the required net open area. Sinn-
larlv, ifthe floor of a mechanical room is below the BFE (with elevated equipment inside) and
a louvered door provides ventilation, Only the open portion cif the louvered door that is below
the BFE will COLInt towards the reqn1red net area of flood openings.
1,
TECHNICAL BULLETIN 1 - AUGUST 2008 17
Figure 13. Stacked vents inserted in
large openings mast be below the BFE
Some FIRMS show mapped SFHAs where the depth of ivater will be 1-Foot deep or shallower,
Although (he difference in rwater depth bet.wvec°n else outside and inside of the enclosure rrr�-
der- a building in these areas will not exceed l foot during the base flood, the 1'�FTP regulations
recltrrre openings.
There are at least Rvo solutions to this situation. The first is to elevate the floor of the enclo-
surf' the nccc:5aaFV height so thatit. is at or above the bFE and there is no need for openings..
The second solution is to install openings, taking care to ensure that all of'the necessary open
area is below the IMF (otherwise the openings will not function as intended). This can be ac-
complished by positioning the bottorn of the openings at or very close to grade, gather than
the rnaxintum of T foot above grade. 1n addition to complying with the: regulations,, the walls
will noL experience: excessive differential hvdraastatic pressure when floodwaters rise higher
thin the BFF..
The `vYF1P regulations identify alternatives to provide sufficient size and number of openings
to allow for the autornatic entry and exit of flood -waters. This section describes how this level
of perfornrance can be satisfied by use of:
Non -engineered openings (or covers and devices) that rneet the prescriptive require-
ment to provide 1 square inch of net omen area 'or each square foot of enclosed area (as
lS TECHNICAL BULLETIN I - AUGUST 2008
descrihed below, a variety of options and devices can serve
as non -engineered openings).
Engineered openings (or covers and dew -ices) that are
specifically clesigned and certified by to registered design.
professional as meeting the required perforralance and
clesign requirements outlined belmv (and, if' applicable,
the ccarnrauarrity's building Code).
Engineered openings (or cowers and devices) for which
an Evaluation Report has been issued by the Internation-
al Code Council (ICC) Evaluation Service, Inc. (IC'C ES),
a subsidiary of the Internanonal Code Council, Inc.
(h ttp: % ; `wti'wwww, iccsafe. card } .
The International
Residential CodeO" Includes
bath the prescriptive (non -
engineered) alternative and
the engineered openings
alternative.
The International Building
CodeO also includes both
alternatives by reference to
ASCE= 24.
The following requirements Czar installation apply regardless oI'wvhether en inecred openings
car non -engineered openings are used to satisf`� the NFTP requirernerats (a so see page 13, he-
quirernerats and Guidance: for Installation ofOpenings):
Each enclosed area must, have a minimum of ovo openings; if there are multiple enclosed
areas, each area must have openings in its exterior walls,
The bottom of each opening must be rlo raacar'e thanI foot above the: hi(? -her of the interior
or exterior z��rade immediately under the Opening, and
Any screens, grates, grilles, Fixed louvers, OF other covers or devices rutast, not block or ina-
pecle the automatic flow of floodwaters into and out of the enclosed area.
It is important to note that FFMA has determined that. certain measures are not acceptable as
flood openings, including:
Standard fotmdaLion air ventilation devices that can be closed manually, because thew do
not allow for the automatic entry and exit; of floodwaters unless they are permanently dis-
abled in the open position,
Standard foundation air Veratilation devices that have detachable solid covers that are in-
tended to be manually installed over the opening in cold weather, because the\, do not
allow Cor the automatic entry and exit of floodwaters when the cower is in place.
Standard foundation air ventilation devices that are designed to open and close based can
temperature (unless they also are designed to allow for the automatic entry and exit of
floodWaters) .
Windows below the: BFE, because the automatic entry and exit of floodwaters cannot be;
satisfied by the expectation that wvincloww.s wc-i11 break under rising floodwaters.
Garage doors cw-ithout openings installed in them, because human intervention is required
to open the doors when flooding is expected. Gaps between the garage door and the door
.lamb or walls do noc count towards the net open area requirement.
Standard exterior doors ww-ithout openings installed in them.
TECHNICAL BULLETIN I - AUGUST 2008 19
Non -engineered openings are openings that are used to satisfy the prescriptive reqUirenicut
that calls for I square Inch of net open area for each square foot of enclosed area. A wide va-
riety of options is available to satisfy the prescriptive requirements.
The Leffn "net open area" refers to the permanently open area of a non -engineered openilla,
The NFIP regulations indicate that flood openings inay be equipped with coverings or- devic-
es pro6ded that they pert -nit the autoniatic entry and exit of floodwaters. The irteasuremenL
of the net open area must take into consideration any coverings that have solid obstructions,
such as grilles, fixed louvers, or faceplates. Rgure 14 shows a Lwpical standard air vent faceplate
and measurements of the net open area.
Figure 14. Typical standard air vent
faceplate (this example provides 42
square inches of net open area)
16.7 inches
6 1 5
inches F"
i J i L J J
LClosure device disabled
in the open position
'-\/fan LITLICtUl-C. I-S of devices intended for use as standard air vents typically indicate the number
of square. inches that each device provides for air flow (either stamped into the metal frame OF
noted on the Z7
packaging). The same number should be LISCd foal i- the net open area calculation
l
%vhen these devices are installed as rion-en uineered openings. Hmvever, in order- to qualify as
flood opening-s that automatic
c entry and exit of floodwiucrs, openings tnust not have I 10
solid covers that are installed durnig cold weacher- Similarly, typical ' air vent clew -ices that are
designed to be opened and closed manually- must be disabled permanently in the open posi-
tion.
Insect screens that do not impede the enti7. and exit of floodivaters are allowed and do not
affect the determination of net open arena. C0111111111116es that administer the International
Buildirig CA.-�" (113U") or the biternational R(�, idential Code' (IRC") should note the require-
ment to cover ventilation openings to keep animals and insects from entering, These codes
provide it list ofacccpLabte covering materials. The commentaries that accompany those codes
note that some covering materials may reduce the 'gross open area of the vent by as much as
50 percent. In areas where floodwaters are expected to carry debris Stich as grass clippings and
0
leaves, it is notable thaL screens tend to clog (Ficylffe 1-5). Local officials may determine that
additional openings are required to increase the likelihood that openings will perforin as ex-
pCcLed, even if some bcconie clog-ged with debris.
171-)
20 TECHNICAL BULLETIN 1 - AUGUST 2008
Figure 15. Typical air
vent clogged by flood
debris
Examples of'several corninonly used non-erigincered openings are described below and 'shown
in Figures 16 through 21:
M Figures I G and 17 show typical standard air- ventilation dex ices that are intended for instal-
lation In CI_aWlSpaCe fiRIndation walls. Ifinstalled as flood openings, they must, be disabled
permanenL V irr L e open position to satisfy L ic requ icinent
for automatic entry and exit of' floodwaters (note that the
device shown In Figtirc, 17 is not compliant because It is not
disabled in the open position).
E Figure 18 shows two examples where the Wilder provided
I
decorative treatment For open holes; in each case, only the
net open area is counted, and, the area covered by the deco-
rative treatment is not. counted.
E Figure 19 shows a common practice for solid perimeter
foundation walls constritctcd of standard 16" x 8" concrete
masonry blocks. Ifa block is omitted as shown, the result-
ing void provides 128 square inches of net open area.
0 Fil-Ure 20 shows where standard blocks are 011-11Cd SideWaVs.
The voids in the blocks are measured to determine the net
open area.
0 FiQ-
1Llre 21 shows a foundation in which a hole was created
when the concrete was poured; a wood frame covered with
screening is inserted in the hole. The framed void is inea-
sured to determine the net open area,
The IRC and IBC (through
reference to ASCE 24) re-
quire that flood openings
are to be not less than 3
inches in any direction in
the plane of the wall. This
requirement applies to the
hole in the wall, exclud-
ing any device that may be
inserted such as typical
foundation air vent device.
Communities usually re-
quire screens over voids
(open holes) that are creat-
ed in walls to serve as flood
openings, to limit the entry
of insects and rodents pro-
vided the screens do not
impede the inflow and out-
flow of floodwaters.
TECHNICAL BULLETIN 1 - AUGUST 2008 21
Grate Louver Grille
r
Figure 16. Examples of typical air vents used as flood openings (net open area varies)
Figure 17. Although this standard air vent was intended as flood openings, it is not acceptable because it is not
disabled in the open position and does not allow automatic inflow and outflow of floodwaters.
22 TECHNICAL BULLETIN 1 — AUGUST 2008
Figure 18. Decorative treatments using fixed louvers and brickwork (count the "net open area" or have
certified as engineered openings)
Figure 19, Foundation
wall with omitted blocks
as flood openings (insect
screen not visible)
TECAMCAL BILLETIA I - AIGUST 2008 2 ")
{stsills z a� s z3x t
sir M,
Figure 20.. Concrete block turned sideways (insect Figure 21. Wood frame with insect screen inserted in
screening shown) opening in poured concrete foundation wall
Openings that are designed ::and certified by a regisrerejd design professional as rne'eung the
perforniance required by the regulations are called "engineered openings." This section
describes certification and documentation requirenrents for engineered openings and the
spdcific design requirernents.
rr- R I VIRTMIM7.71r,
For architectural or other reasons, building designers or owners may prefer to use unique
or individually designed openings or devices. In thcsc, cases, a registered design professional
must submit a certification. As a general rule, Mates require a designer to he licensed to prac-
tice in the Mate in which building is located.
The original certification of the engineered openings nrtrst include the design professional's
name, title, address, signature, t�°pc oflicense, license nurzalacr, the State in which the: license
was issued, and the signature and applied seal ofthe cerrifVing registered design professional.
The certification shall ldenti V the building in which the engineered openings willbe in-
stalled. The language of the certification shall address the following:
A staterrnent certitVing that the openings are designed to automatically equalize hydrostat-
ic flood loads on exterior- walls by allowing the automatic eritr v and exit of floodwaters ill
accordance with the Engineered openings, design requirements on page ` 6,
Description of the range of flood characteristics tested or cornputesd for which the certifi-
cation is valid, such as rates of rise and fall of floodwaters, and
Description of the installation requ Mnents or limitations that, if not followed, will void
the certification.
24 TECHNICAL BULLETIN 3 - AUGUST 2008
Engineered openings or devices may be accepted by local
officials as an alternative to non -engineered openings (pre-
scriptive) provided the designs are certified. The certification
rnav take the form of the individual certification described
above, or it can be an Evaluation Report issued by the WGES.
The ISSLIeS SUCII reports for a variety' of building prod-
acts, methods, and materials. Evaluation Reports are issued
only after the IC GES performs technical evaluations of docu-
ryientation submitted by at manufacturer, including technical
design reports, certifications, and testin- that demonstrate
code compliance and perfortriance.
Evaluation Reports are supported by ccrLificaLiOris that in-
clude appropriate language describing performance of the
openings and the name, tide, address, type of license, license
number, the State in which the license was issued, and the sig-
nature and seal of certifi,7ingt-egi.stei-edclesi!LylI DFOCeSS1011al.
The specific provisions that are addressed in the certification
intist include:
ICC-ES has issued
Acceptance Criteria for
Automatic Foundation Flood
Vents (AC364) for one type
of engineered opening. The
]CC -ES will develop ac-
ceptance criteria for other
types, upon request.
Local officials in communi-
ties that do not administer
the International Code
Series determine whether
to accept building prod-
ucts that have received
Evaluation Reports issued
Ivry the ICC-ES.
E A statement certifNing that the openings are designed to automatically equalize hydrostat-
ic flood loads on exterior walls by allowiMY the autornatic critry and CXiL of floodwaters in
accordance with the Engineered openings, design requirements below,
1 0 0
M Description of the range of flood characteristics tested or computed for which the certifi-
cation is valid, Stich as rates of rise and fall of floodwaters, and
E Description of the installation requirements or limitations that, if not followed, will void
the certification.
An imporlant part ofthe evidence riecessary to document compliance is the certification of
engineered openings or the EwAuation Report. A copy of the individual certification or the
Evaluation Report, is required to be kept in the cominunityT's permanent permit files, along
with inspection reports. The documentation can be submitted as part of the permit applica-
tion and design dravvino-s, Or submitted separately. Owners should retain the certification or as
copy of the Evaluation Report to subrnit along with applications for NFTP flood insurance.
Insurance agenis will request that property owners provide docurnentation as part of appli-
cations for NFTP flood insurance. The dOCLImen(ation should be attached to tyre Elevation
Certificate. The following are acceptable forms of documentation:
M For engineered openings with individual certification, the certification ication described above
that is signed and sealed by a registered design professional who is licensed M the State
where the building in which the engineered openings are used is located; or
TECHNICAL BULLETIN 1 - AUGUST 2008 2-7)
M For engineered openings with TCGES Evaluation Reports, a copy of the Evaluation Report
that docutnents that the engineered openings meet the performance requirements of the
NFIP and the building code, and that specifies the nurriber of such openings that are re-
quired for a specified square Footage of enclosed area below the BFE; or
0 For engineered openings kwh ICGES Evaluation Reports, a letter or other written eNi-
deuce frorn the local official that use of engineered openings in a specific building is
acceptable.
,111■, 1 *1111 111, # a
The American Society of Civil Engineers (ASCE) developed the standard Flood Resistant Desig-11
and Construction (ASCE 24). This standard applies to buildings and site developments pro-
posed in flood hazard areas-, it is re ferenced by the Code. ASCE 24Section
2.6.2.2 contains installation and design criteria for engineered openings. ASCE 24 provides
n,
the equation below to determine the total ii(-,.t area of engineered openings that are installed
in foundation walls or enclosure walls. The equation Includes a coefficient that corresponds
to a factor of safety of,), which is consistent with design practices FChIWd to protection of life,
and property. This factor of safe rly also helps to account for the likelihood that insect screens
riiay clog wiffi flood -borne debris. The ASCE 24 commentary provides additional backggrotrncl
on the derivation of the equation.
A-s with non -engineered openings, engineered openings must be designed to allow automatic
entry and exit of floodwaters.
Three design and performance criteria Isar enyineered openings pare specified in ASCE 24 but
are not explicitly identified III the, NNFIP regulations:
• Engineered openings are to perform sttch (hat difference between the exterior and inre-
rior water levels shall not exceed I Foot during base flood conditions.
• Encyineered openings are to be not less than 3 inches in any direction in the plane of the
wall. This requirement applies to the hole III the wall, excluding any screen, grate, g)-ril1c,
louvers, or devices that may be placed in or over the opening.
• In the absence of reliable data on the rates of'rise and Fall, engineered openings are to be
desi,gricd based on the assumption that the inkiiinuni rate of rise and fall wrill be 5 feet per.
liour. Where data or analyses indicate more rapid rates of rise and (all, the required nurn-
ber of openings is to be increased to account For those different conditions. The number
or size ofthe openings niav be decreased if data or analyses indicate rates of rise and fall
are less than 5 feet per hour.
26 TECHNICAL BULLETIN I - AUGUST 2008
From ASCE 24, the equation to determine area of engineered openings:
A0 = 0.033
Where: A, = total net area of openings required (in2)
0.033 = coefficient corresponding to a factor of safety of 5.0 (in2 - hr/ft3)
R = worst case rate of rise and fall (ft/hr)
A e = total enclosed area (ft2)
[ASCE 24] Table 2-2
Flood Opening Coefficient of Discharge
MMRM..� >�
C
circular, unobstructed during design flood
0.60
rectangular, long axis horizontal, short axis
0.40,
vertical, unobstructed during design flood
square, unobstructed during design flood
0,35
rectangular, short axis horizontal, long axis
0.26b
vertical, unobstructed during design flood
other shapes, unobstructed during design flood
OM
Notes:
a. When the horizontal dimension is twice or more the vertical dimension, use
0.4; as the dimensions approach a square, interpolate from 0.4 to 0.36.
b. When the horizontal dimension is half or less the vertical dimension, use 0.25;
as the dimensions approach a square, interpolate from 0.25 to 0.35.
Used with permission from ASCE.
TECHNICAL BULLETIN I — AUGUST 2008 27
The U.S. Congress established the N;FIP with the passage of the. National Flood Insurance
Act of lgfi8. The NFIP is a Federal program enabling property owners in participating com-
munities to purchase insurance as protection against flood losses, in exchange for State and
community floodplain nranagerient regr.rlations that reduce future flood damages, Participa-
tion in the NFIP is based on an agreement between communities and the Federal Government.
If cOn-rMttnitt- adopts and enforces adequate floodplain managemc nt regulations, FEMA will
make flood insurance ar,ailable within the connnUnitV.
Title 44 of the C'.S Code of Federal Regulations contains the NFIP criteria for floodplain man-
agement, including design and construction standards for new and substantially unproved
buildings located in SFHAs identified on the. t`v'FIP's Flood Insurance Date Maps. FEMA en-
courages communities to adopt floodplain m an<agement regulations that exceed the NFIP
criteria. ,As an insurance alternative to disaster assistance, the NFTP reduces the escalating
casts of'repairing damage to buildings and their contcnts caatrsed by floods.
1► 1i'` r ` i f .TIlaM
This is one of' a series of' Technicatl Bulletins than FEMA has produced to provide guidance
concerning the building pert€>rntance requirements ofthe NFIR These requirements .are con-
tained in Title 44 of the U.S. Code of Federal 1:egulations at Section 60.3. The bulletins are
intended for use by State and local officials responsible for irrterpretinti and enforcing the re-
quiremems in their floodplain management regulations and building codes, and by 1-nernbers
of the development community, such as design professionals and builders, New bulletins, as
well as updates of e xisting bulletins. are issued periodically, as necessary, The bulletins do not
create regulations; rather, they pr€ Vide specific` gtri€laance for comptving with the reclr.rii-enients
of existing NFIP regulations. 1. stirs of the Technical Bulletins who need additional guidance
should contact their NFIP State Coordinator or the appropriate FE.NIA regional office.. The
fscr' Chide to C�( tzical Bidleti.ns (Izttp:/,,'�ti 4 �.fcrn a. taw/pclfffinalf'guide%ll.pdf) lists the laul-
letins issued to bate..
The quickest and easiest ways to acquire copies of FEM.1's Technical Bulletins is to down-
load them from the FEMA website (hap:;`,iwwi .featia.�trv/l�lati/1�3-e lent/tlooclplaiii/techhul.
sl�rtrn) .
Technical Bulletins also mays be ordered free of charge from the FEMA Publications kVare-
house bil calling 1-800-480-2520, or by faxing a request to 301-362--53 ,5, Nlonda�T through
Friday between 8 a.m. and 5 p.na. EST. Please pro:)vide the FEMA publication number, title,
and quantity of each publication requested, along with VOUr nanic, address, rip code, and day-
tune. telephone number. tVriterr requests may be also be submitted by mail to the following
address:
` 8 TECHNICAL BULLETIN I - AUGUST 2008
FENMA Pr blicarions
P.O. Box 2012
Jessup, `AID 20794
The following sources provide further information concerning openings in COUndation walls
and walls (-A enclosures.
American Society of'Civil Engineers, Structural Engineering Institute. 2005. Flood Resl"Slant D(-
Sij�i2 and Construction, ASCE/SEI 24-05.
American Socicty of Civil Engineers, StFUCLUral Engineering Institute. 2005, Alini-mion Design
Loadsjbr Buddingand 01hei- Sirtict-it'res, ASCE/SEI 7-05.
FEMA. 1991 . A nswery it) Questions About SubsUmliattly Damagrd Buildhigrs, FEMA 213.
FEMA. 2000, Coastal Conslructiort lWanual, FEMA 55(.,D (3rd edition).
FENIA2004. PoodlVal.",,vi jl,;Imi(rgorm.ent Btdleh"W Elevation (JertO'cate, FEIVIA 467-1 (http:'/1/1NAVW.
f'cnaafi. gov /pdf--,./fimaI /fema46'/-6-l0-04.pdfl.
I') I
FEN -Lk. 2005. Home Builders Guide to (,oaslal Consimclian: Tc•hni('td &u-(.sheet ,series, FEMk 499
FEM-A. 2006. Elevation Cer(ijicate (FENLk Form 81-31, hctp://N4iti,it.,.fet-na.gov/'pd('./tifipfelvcert.
shtni).
RX'Evaluation Service, Inc. 2007. A cceldance Critr�ria ' fi)-A )utoix?(zlicFt)t(,ri(l(tlionl-7oo(I i' nls (AC364,
hup: "criteria/pff files /ac364.pdf).
International Code COLIFICil, Inc. 2006. h-d.en?allorzal Code" IBC"2006,
friternational Code Council, Inc. 2006. International R(�sidpnfial Code', IR(,"-' 2006
National Fire Protection Association. 2005. A,1w,/(,1 Nfizrzyftiaurpd Homu, htstallation Standar(117
NRIA 225.
National Fire Protection Association. 2006, Buildh,,g Construction mul)(zjety Code`, NFPA 5000.
TECHNICAL BULLETIN 1 - AUGUST 2008 29
Accessory structure - A structure that is on the same parcel of property as a principal struc-
ture, the use of' which is incidental to the use of the principal structure.
Base ood - The flood having a I -percent chance of being equaled or exceeded in any given
year, commonly referred to as the "I 00-vear Hoo(-L" The base flood is the national standard
used by the NFTP and all Federal agencies for the purposes of requiring the purchase of flood
insurance and regulating new development.
Base ood elevation (BFE) - The height of the base (1-percent annual chance. or 100-year)
flood in relation to a specified daturn, usually the National Geodetic Vertical Danim of' 1929
(NGNT)), or the North American N."er6cal Daturn of L988 (NAND).
Basement - Any area of a bUildiffi; having its floor subgradc (below ground level) on all
sides.
Elevation certi sate - A form developed by FEN[A to collect surveyed elevations and other -
inform ation about a building that is necessary to obtain flood insurance.
Enclosure or enclosed area -.'Areas created by a crawlspace or solid walls that fully enclose
areas beloAv the 1317E.
Federal Emergency Management Agency (FEMA) - The Federal agency that, in addition to
carryiM-Y Out Other activities, administers the National Flood Insurance Program.
Flood Insurance Rate Map (FIRM) - The official rnap ol'a community on �N,,hich FEINIA has
delineated both the special flood hazard areas (SFHAs) and the risk premium zones applica-
ble to the community
Hydrodynamic load The load imposedon an immersed object,."'Lich as a foundation element
or enclosure wall, by water flowing against a.nd around it. The magnitude of the hydrodynam-
ic load varies as a function of'velocivy and other factors.
Hydrostatic load - The load imposed on an iminersed object such as an enclosure wall, by
standlin, or slowly inoviin-water. The magnitude of [lie hydrostatic load increases linearly t6th
water depth.
Lowest oor - The lowest floor ofthe lowest enclosed area of a building, including: a basenien t.
Any NFIP-compliant unfinished or flood -resistant enclosure usable used solely for parking of
vehicles, building access, or storage (in an area other than a basement) is not considered a
building's lowest floor, provided the enclosure does not render the structure in violation of
the applicable desig-ii requirements of the NFIP.
Mitigation Directorate - The component of FENTA directly responsible for administering the
flood hazard identification and floodplain management aspects of the NFTP.
10 TECHNICAL BULLETIN 3 - AUGUST 2008
Net open area - The permanently open area of'a non -engineered opening intended to pro-
vide automatic entry and exit of floodwaters.
Opening, engineered - An engineered opening is an opening that is designed and certified
by a registered design professional as meeting certain performance characteristics related to
providing automatic entry and exit of floodwaters; the certification requirement may be satis-
fied by an individual certification or issuance of an Evaluation Report by the IC:CA Evaluation
Service, Inc.
Opening, non -engineered - A non -engineered opening is an opening that is used to meet.
the NEIP's prescriptive requirement of I square inch ofnet open area for cver�square foot of-
eraclosed area.
Registered Design Professional - An individual Who is registered or licensed to practice their-
respective design profession as defined by the statutory requirements of the. professional re--,
ist.ration laws of the State or jurisdiction in which they project is to be constructed.
Special Flood Hazard Area (Sl~HA) - 1n area delineated on ra EIRNI ( as being subject to in-
undation by the base flood and designated as Zone: A, AE, AI-A30, AR, AO, AH, A99, V, VE,
or VI-V (?.
Substantial damage - Damage of any o6gin sustained by a structure whereby the: cost of re-
storing the structure to its before -damaged condition woulcl equal or exceed 50 percent of
the market value of the structure before the damage. occurred. Structures that are determined
Lobe substantially damaged are considered to be substantial improvements, regardless of (hc
actual repair work performed.
Substantial i€raprovernent - AnY reconstruction, rehabilitation, addition, or other inaprove-
rrent of a structure, tlae cost of which equals or exceeds 50 percent of the market value of
the structure (or smaller- percentage if established by the community) before the "start of.
construction" of the: improvement. This term includes structures that have incurred "substan-
tial damage," regardless of the actual repair -,a-(..}rk perforrxred.
TECHNICAL BULLETIN I - AUGUST 2008 31