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Item H10AGENDA ITEM SUMMARY Meeting Date: September 16, 2015 Department: Building Bulk Item. Yes X No Staff Contact Person/Phone #: Christine Hurley, 289-2517 Ed Koconis, 453-8727 AGENDA ITEM WORDING: Approval of a resolution of the Monroe County Board of County Commissioners adopting FEMA Technical Bulletin 9 "Design and Construction Guidance for Breakaway Walls" 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 technical 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 move forward with the intent of becoming eligible to enter FEMA's Community Rating System (CRS). The proposed resolution would adopt FEA Technical Bulletin 9 "Design and Construction guidance for Breakaway Walls" 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 flood 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 Floodplain management, CONTRACT/AGREEMENT CHANGES: N/A TOTAL COST: N/A INDIRECT COST: NIA BUDGETED: Yes No N/A DIFFERENTIAL OF LOCAL PREFERENCE: COST TO COUNTY: N/A SOURCE :, FUNDS: REVENUE PRODUCING: Yes No N/A AMOUNT PER MONTH N/A Year APPROVED BY: County Atty q OMB/Purchasing Risk Management_ DOCUMENTATION: Included X Not Required DISPOSITION: AGENDA ITEM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21, 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 MONROE COUNTY, FLORIDA MONROE COUNTY BOARD OF r RESOLUTION NO. -2015 :F < r r ii � r ;• r 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; NOW, r r BY THE :#<!r OF COUNTY COMMISSIONERS OF MONROE COUNTY, FLORIDA: Section 1. Pursuant to Monroe County Code Section 122-2(c), the Board hereby adopts FEMA Technical Bulletin 9 "Design and Construction Guidance for Breakaway Walls" 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 16"' of September, 2015. Mayor Danny L. Kolhage Mayor pr•o tern Heather Carruthers Commissioner Sylvia Murphy Commissioner George Neugent Commissioner David Rice i•'f i i i Lei Is7li Mayor Danny L. Kolhage (SEAL) ATTEST. AMY HEAVILIN, CLERK. Deputy Clerk • Below Elevated Buildings Located in Coastal High Hazard Areas in accordance with the National Flood Insurance Program Technical Bulletin 9 / August 2008 FEMA NFIP Regulations ............. ----..—.—.__---------------------3 FlwmdTmuurance Cousiderad*us..... ----------_-----.......... --.......... —4 Building and Reaidco6a]Code Con.,,,idoroduou—.... ---_....... ........................... --5 \,Vave Loads on Building Ekncmts......... ..--__------...................... ____ —'5 PerOornnaoceo[Bnc �Va\lu—_........................... ................................ ------5 {)ndoostorEnclosing Areas Below Eievaced8c11lc11u8's... --.............. -------'l2 Prceci dve Design Bfeduod[mrBrc NN',Jl. ............ ........ ................. ---....... _l3 SimupliGcdT)csiAulJeihw|f"orBreaka\vay�Vals.... ...... ... --... —......... —_—_... —l8 Pc Dc, a[Brc .-----_—.............. 25 %o�paccm[� l4�l]�rcx6u�x�smm{)x6ccDu�\��zlu E]eoicois ..... .......... ........... 26 (onatruc600Nfalrt-la{s......... ---------------...... -----_—................. 27 Exisdog8uOdinus R�ouico'�ccoodchu�./1dd�doms,aud��tmz6cdo�--------Z8 Rceonuoucudad000[brCmumudAZones .... ........ ....... _---_............. .............. _28 TheN[IP _........ ---------............ ................................... ......................................... �3O NFlPTechnical Bulletins ..—..—.-------------------------------�3U [)rdccioo-TecboicaiRuDedrs ........ --....... ----...... _.................................. —_----3l Fordierlo6oconahoo ... ......... ....... -------_-----.................. ...... ...... -------�% Glo» ary-------_-------_-------_—__--_-----_---_—__—__32 Comments on the Technical Bulletins should be directed to: Department ufHomeland Security FEMAMitigation Directorate 58OCStreet, SW. VVaahingtun, D,C.2O472 Technical Bulletin 9-O8replaces Technical BuUebn9^DB. Design and Construction Guidance for Breakaway Walls. Cover photo: Post -Hurricane Ivan photo of the underside of an eievated V zone building. The break- awaywm|[aundernmothUhebui|dingbaDedaain1emdeddudngthehunimane. Pro[ectincr bttildii-ro1-) -S that are C0171SO-11CCeCt HI special flood hazard areas (SFHAS) frfromdaryl- 0 age caLI.SCd by flood forces is an inipor-Lant olhjective of' the National Flood Insurance Program) (NFIP) , In stipport of' this objective, the NFIP regulations include influrnurn bUilditloy design criteria that apply to new conso7ticnon, repair of'sLtl)stantially damaged buildinco, and Substan- tial irnprovernent.s of'existin ' cy brii1dings in SFHAs. The hale flood is vised to dea llnere SFHAs sari Flood 111SI-trance Rate Maps (FIR.N4s) pi-epared by tire NFIR The base flood is the flood thar has as I -percent chance ol'being equaled or- exceeded in any given rear (corni-norik called the 100-year" flood). Certain terfrIS (Ned In this Technical BUlICLIn are defined in the Glossary. Coastal waves and floodino- can exert str-on(y hvdr-och-narnic I-'(,)rces on any [)Lrildill� elenient that is exposed to the waves or flow of water. The NFIP reqTfires that all new bi-lild.ings, SLII-astanfiallv clarnaued hirildhio-s, and stibstantially irnproved IXJIldIfi(_, in Coastal H'oy i Hazard kreas (Zoncs V, \T_ and VIOMI) be elevated to or above the hose flood elevation (BFF) 01) 01,)CH FOLL11(larions collsistill(,F of, plies, posts, , piers, or C(.,)I- unins. These open COWICIaLionS niust Lie designed to allow �n waves and water i-novine at. high velocity to flow beneath ho-tild- ri vs. NFIP rc(Yiil- aLioris require that the area below the lowest floor (_)I' ele7ated bihIdinIgs either he free of obstruciloris or have a n ' t, enclosed areaS br' cOHS[rticced Of DOVI-SLIPPOrting break- aWalv walls, open lattice -work, or insect scrccnIr1,,,. The walls, lattice, or screening are Intended tea collapse under Wave loads Under the NFIP, the "low- est floor" is the floor of the lowest enclosed area of a building. An unfinished or flood -resistant enclosure that is used solely for park- ing of vehicles, building access, or storage is not the lowest floor, provided the enclosure is built in compliance with applicable requirements. WILtIOUL cai-isirig col apse, (lisptacCHICUL, Or. O[IICF S(RICLIrrat darnage to the elevated bnilding Of the SL[pl)OI'tInIY I"0Mi(kt- rIMI SVSICrTI (see FIgUI-C. I ). ()l_)StFII(.Ar0tis I)clow an elcvated bLlildill- can sio-rtificantiv increase the potential Or flood daniac-e IDV irlffea,ing the S1.11111CC <AreaL MIN ave HI -Met, and vc- ject, to W_ II Ho%�. The NFIP re-Itlations a.dso spc city th,t] e11Cl0SIH_eS may be Itsed only for- p,11-king of' vehicles, httildivig- access, or storage, that all rnaterials below the BFE, incttidinl- niaterials used to con- sn-tict enclosures, he flood Clarrialge-i-esisLarit materials; and that construction. nictliods and practices irfinitnize the potential for flood clanlage Specific design reqitirernents Cor breakawav walls are inchicled in the NFIP reorldaLIOCIS. Th OSC pararneters were the srtbjecrof research on breakaway walls perf'Ornied lot- the Federal Erner- gencv (FEM-k-) aird. the Nat.ional Science Fotindation lDv North Carolina State LTniversiry and Orc,-on State L"nivers1tv (Tting et al., 1999). The research cvaliiated fail - (.are mocha nisms that IVCT-C de t-no.)nstraLed bV ffill-SCale, laboratory wave -tank tests of'breaka,,vav wall Panels Technical Bu I I eTin 9 — a uGu ST 2008 Floor support beam Vertical foundation member B18= This Technical Bulletin presenis three design rnethods that are consisr.eni with the NFTP regulations: a piescripl.ive design approach, a sinipillied design approach, and a per a lice - based design appr(-)ach. Re-clrdless of the approach used, breakaway walls nitLst l-)e designed and const.rucl't-d t,o nleet applic-11ble bifflding or- residential cocies, such as the International Building Cod&' JBCl or the International Residaitial Code-: (IRC��) . respectivelv. In niativ cases, design wind speeds will exceed the prescriptive unlit; Specified in the (YOV(.1rilill ' g Rsidenaial codemeans, which de,i(lrlS MUSL l)(-' ire �ICCOrdance with the governing building code Or other appr(-wed sLandard, For CM1111PIC, Lll(-' PreSCUiptiVe design pl-OVisiOns ofthe 2006 IRC are not <-.tpplicahlt, uo designs where `)-secoild grist deslIgn 'wind speeds exceed 100 niph-, thLls, residen- tial .structures iii these aveaS HILLSt he (ICSI-ned ill. 2LCCOUdance Mth the IPW. oi- othei- standard 9 Technical Bul I eTin 9 — auGuST 2008 referenced in the IRC" (see IRC Section 1'.30121, I) . The. priniary t eferenc c for wind and seis- mic loadimy in buildino- arid residential cocles is Minimum Dian Loads for Buildings and Other Structures (,CSC i-f} 5) . The prescripti c design approach for breakawaa, svTalls regnires the use of t-spiral detailing, bUt allmvs the designer to design the elevated portion of the home and the fMmdat1017 systerra without. consideratis�n of flood forces acting on the brcal a3+av walls. This approach i.s € my al- kmved for walls designed to have ja safe loading resistance (also referred Co as allowahle load) of ` 0 pc3unds per square foot (psf) or less, as defined in this Technical Bulletin The si rtplihed design approach is permitted for walls designed tca have a safe loading resis- tance of more than. 20 psf. The approach regnires the nse of u.ypicaal details that are similar to those used in the prescriptive method. Although special certification is required for these Ws 11l>, the prc)ecss is ,Simplified sine these walls are designed to minimire flood loads to the elevated stratc-ttare and fomndat.ion systenl. The perfOrtnance-based design approach all+ i,s more detailing freedom for l3real as,ay walls, taut rcyiire.s the designer to consider the coratl-..)fined effect of`Nvind forces acting can tltc. elevat- ed portion of the st:rttc.trtre.-, as well as t,ind and flood loads acting can the f(_')ttnd<atic.an s,stern and the hreaka,-,aa, walls. The N IP regnlaat can, for hreakaav,'a.y Walls are codified in Title A.4 ofthe Code of Federal llte"_U- lations, in Section 60.15(e) ( 4), wVhicla states that a community shall: ``Provide that all new construction and substantial improvements in Zones VI-V3f} and VE, and also Zone V if base ood elevation data is available on the c0111axtunity�'s FIRM, are elevated on pilings and columns sothat (i) the bottom of the lowest horizontal struc- tural member of the lowest czar (excluding the pilings or Columns) is elevated to or above the base ood level; and (i'i) the pHeor colttntn foundation and structure attached thereto is anchored to resist otation, collapse and lateral movement due to the effects of wind and water loads acting sirt11.11taneously on all building components. Water loading, val- taes shall be those associated with the base ood. Wind loading values used shall be those required byapplicable State or locaf building standards. Aregistered professional engineer or architect shall develop or review the structural design speci cation s and plans for the construction, and shall certify that the design and methods of construction to he used are in accordance with accepted standards of practice for .meeting the provisions ofparagraplas (e)(4)(i) and (ii) of this section.,, Section tiff. >(e) (5) f`tartkter states that a c:c:MMUnitvshalll require: that all nevv construction and substantial improvements within Zones VI -V-ai), Vp, and V on the cornmu n ity's FIRM have the space Flow the lowest oor either free of ob- struction or constructed with non -supporting breakaway walls, open wood latticework, Technical But i eTin 9 — auGuST 2008 3 or insect screening intended to collapse Lin der wind and water loads Without cattsiM; col- lapse; displacement, or other structural darnagieto the elevated portion of the building or supporting foundation systen.. ror the purposes of this section, a breakaway wall shall havea desigtl safe load ingresistanccofnot lessthan 10 and nomorethan 20 pounds per square foot. Use of breakaway walls which excel a desigan safe loaduag resistance of20 pounds per square feat (either by desip-i or when so required 1 y local or State codes) may, be permitted only if a reggistered professional engineff or architect certi es that the designs proposal rneet the following conditions: (i) Breakaway wall collapse shall result fi-orn a water load less than that which would occur during the base ood; and (ii) Theelevated portion of the building and supporting foundation system shall not be subject to collapse, displacernent, or other StrL[CtLiral damageductotheeffects of wind and water loads acting simultaneously on all building components (structural and non-structural). Water load- ing values used shall be those associated with the base ood. Wind loadingvalues used shall bethoserequired byapplicable State or local building standards. Such enclosed space shall be useable solely for parking of vehicles, building access, or storage" Propiosals liar snb.stantial improvement of existing- 1:)ctildings in Vzorres, and, proposals to repair those N,illdingl; that have sus- t:aained stth.staannal elatrria ge, inrtst Cot 11PIV With the requirements for riew consrrucborn, includin requirenresnts Bear° l c°akawaav walls stirrm,niding e°aicicased areas hcloww the BFE. As part of issuing permits, corrrrnw1ity officials must review stach propos- als to determine whether tlIe)F ecaMPIN' ww-ith the rcquirernents. F'rn-ilic-r infi,ar-niat.ion oil Substantial improvement and substaall- tiatl damn age is I'caund in Answers to Questions About Substantially Damaged Buildings (F'&_NIA 21 )). 19 &�a w �.r The NFIP Technical Bulletins provide guid- ance on the minimum requirements of the NFIP regulations. Community or State requirements that ex- ceed those of the NFIP take precedence.. Design proles- siorals should contact the community to determine whether more restrictive provisions apply to the building or site in question. All other applicable require- ments of the State or local building codes must also be met for buildings in all flood hazard areas. Flevate€l buildings in y, zones that do rae>t hale obstrucrimis ear ericlosur-es 1ae5lovc tyre 1-aIAF. are sti.Nect. Lc) less flood daniaae and thus lower rapes are used t.o ctcterinitae premiums tier NFfP lleacad insurance. Some consicle'rations a€(feeling- the raaLes and costs of NFIP flood insurance f<ar c.lc°,ated buildings in V zones include: n The use of an c°ttclosure wVlch bFCakaww-a% walls increases t.he premium foi• the entire l)aaiIding. n An increase in tits fh-iod insurance prernurn rresultini; from the presence of ari enclosure dcpernd,b U130i. the area cal tile' encicastrre; SUbSiLantiatl1 hi(,cn- lire raaittrxa:a aare. Chaarged fear- enclostta-es that are 300 square feet Or l;reater ira area. n The presence of g.ararrge cicmrs belmv an elevated 1lrtildiii , €°veer if desianed in accordance with this Technical I'ullctirn, rnav increase the flcreacl irrst€ratnc:e prernit€rn year- date latxilehng. NFIP flood insurance I:>talicies have limos cats covera ry of`ccrl atellts ill enClc.�satVeS Under eleVtiIt- eel 1Au11dirl';:s. ticsilryner:s, coiitratictors, and owners ma.wj Wish t.0 cc>rlcaact a qualified insurance aal;ent or the NFIP fear more information atlntlttt polio coveratle, coverage lirnits, and costs. 4 Technical BulleTln 9—auGuST20CE; WENT1 M m IN "I I M, The IBC: requires that hreakaway walls he designed and deiailcd in accordance with Flood Re- sistant Desigm and CotistrUction (ASCE �4-05 ASCE 24-05 provides minirtmin reqU11'el-rients for flood -resistant design and construction of structures that are located in flood hazard areas. It requires breakaway walls and [heir connections to be in accordance with the flood loads spccl'- fied in ASCE 7-05. In addition, .SCE 24-05 states that Ltllfincs and <ItLelldani equipment shall ,)t be mounted oil, pass dirough, or be located al.(.)iil- breakawav walls. The TRC. contains NTIP-consistcnt provisions and rCCjUiR-,,s that the design of'breakaway walls 0 be certified by a rCO-iSterCd deSigIl Professional if -wind loading values exceed 20 psf- As an al- ter the IRC' per i-niEs the use of ASCE '24-05 fOr tile design Ofbt-Ca.ka\VLV Wa111S. It ShOtild be noted that component and cladding va]LICS presented in the IRC exceed 20 psfin locations wherc, die 3-second dust desi-n wind speed equals or exceeds I 10 itiph. BUildings in areas where condiLiOHS produce breaking waves are exposed to different, loads and more severe loads than are Unposed ors bUildings areas without Avaves. As 1) in flood hazard at a twcakin'(7, wavc passes a pile founclation or other element of an open foundation, the struc- ture experiences an oscillat.ing, high -velocity flow that peaks at the the w Waasave VC cl-Cst"dust a hi-eaks. While drag forces are imposed on the relativeIN- narrow verfical surfaces of open [01.111- dations as water moves Under the building and past the foundation clunicius, most ofthe flow is relatively , undisilti-bcd, �,vhich makes open foundations =in appropriate design in N' zones. Water HOWs past piles under a building in r1ILLCh the, same r,vuv rivers flow past piles and piers Used to SUppOrl brill -es. I The effect IS ClUite CHITCI-C111 When a bi-cakinty wavc hits a wider, relatively corlfiy.ILIOUs, vC.t-ti- cal surface, stich as as wall. t,1711CII the (_i.eS, I ofa breaking wave irnpacts a wall, as pocket. of'air is trapped and compressed by the wave (see Figure `?).:Vs the air pocket collapses. an exceed- 111-ky high-pressilre I)Ll,rsL (Le., Shock wave) impacts the wall, with the force ceriLerect around the stillwater level. Peak pressures from a 5-foot breaking wave can he 100 Miles 111-11CF than the safe loachm, rcsistancc of 1. 0 to 20 psfthat is specified for brcaLLWav walls in the NFIP reg- UIL-16erns. MIM-01 �Iwm �1-7=1 FENIA deploys Mitigation Assessinent, Teams after some disasters u.) evaluate the performance ot'huildings and related infrastructure. MAT reports pCepal-e(I after sl'gm[icant COaSULl StOVITIS haVC. consist.cuLly concluded that breakaway wall SVSLCl-lIs perform as imended when they are designed and constructed to break away withour darnaging the elevawd home and without 1. In becon-tinu debt-'s that can be trapped tit M I under buildings'. Figurc 3 shows an example Of'SUccess- ftil breakaway wall performance. MAT reports hav'e also shown that some breakaway walls have been desk-4-ned, constructed, or modified in w-ays that conflicr with the. NFIT) regulations, ]it rilany cases, these riori-comphant �valls have led to unnecessary damage to, or collapse of, elevated structures. Technical Bu I I eTin 9 - a uGuST 2008 5 Figure 2. Impact of a breaking wave on a vertical surface Figure 3. Successful Wave crest fi dJ Stillwater elevation Center of high pressure burst Trapped air compressed by wave Ground Vertical surface The nrost. coitirnoiitv Prolflel'TIS ilivOlVillIcy N-CAMvat vv-all systerTis are caused I-.)y poor deL-,Uhiig practice,-,, inappropriateIV COCISLRICLed addiLlons, or, rather CMISI[FUCtron leatur-es, SUCII practices do noL coiriply with the letter- or illtent of, the NRP which require trcac.tnres to he -coiisn-Licte(� lDv rriethods and practices that niininiize flood dai-riaocs." RgUfVS 4, tllT'(,)L,Ilc'rll 8 illLlstvacc sonic; of (lac iion-coinphatit coll'structioll prolAcnis that have been ilhistrat.ed in MAT reports. 6 Technical Elul I eTin 9 — auGuST 2008 n Figure 4 shows access stairs, supported by cornponem, walls that were not designed and detailed to break aw,N,a'Yfrotn the strucLure. To be compliant wlih the NFIP's fi-ec-ol-lobsti-tic- Lion i eqnIFCn1t',IIt, Slall-S []]List be desiLgried to eidier 1-Teak away or to independently resist flood loads a.nd to minfi.nize transfer of loads to [he structure ffor more int'ormation, see Technical BLilleLhi 5, Free-of-Obstructim Requiremems for Buildings Located in Coastal Higli Haz- ard Areas). It shotild, also I,-)e noted that the backfilled concrete masonry tunc walls and planter mav also slgnificatalv alLCT LhC flow ol'ivater toward adjacent, structures, n Fig -Lire 5 shows, damage to exterior- wall covering caused by lack of"a horizontal separation joint Mot 'DCt-WCCII the I)FC21k3wav wall and dic, wall above. n Figure 6 illustrates what is probabh the most common prol--)lcm that contributes to darn - age - poor detailing- practices. In this eX-,Ln1ple, Ufflities were aLLached LO the be-eakaway VV<IIL Sin111a1- (Umtige is caused wvheti mility lines are rim throLigh access holes, which thee] prevent the Walls From breaking away. All utility COMPOnCrIUS that nitum be nisiallcd below the elevated st,nicnorc nitist be flood darmLgc-resistant, dt...siglied for flood f'orces' and at: tached to permanent structural elements on the side opposite to the an Licipated (Ilrecti011 of'flow and wave approach. n Figure 7 shows cross braces that were installed Inside the bi-eakaway walls and that could hrivc prcvcn(c.d ulic breakaway walls froni pCrforriling as designed. Braces, when reqLLired I- -)e installed -fffe With LhC intended peFf-or- )v the structural desi-ii, n-iust t illed so as not to ItILCI I I RIMICe of hretLkmvav walls (.see TechniCal BLIlletin 51), n FI'g-urc 8 shows a (ICUL111no practice NAIICFC the N-CakaWaVW2111S SpaIMCCI across vertical foun- CLUtOn elC111CIAS, I-LnTICC(-',S�SM-i1V Sti-ello-d-I Cri in ly the breakawav wall and preventing it frorn Perl'01-MILIO, as Intended. 11 Technical Bull eTin 9 - auGuST2008 Figure 5Non- joint detailing Figure 6. Non- GOMPliant utilities attached to breakaway wall Technical Bul I eTin 9 — auGuST 2008 Figur O. Non- compliant broakoway wall spanning across avertical foundation element Technical Bo[|eTln 9—muGu8T2808 9 Early analyses ofbreakawaw, walls assumed base flood conditions and Oscillating (rion-break- m1g) wave conditions. More recent research conducted hv North Carolina State University and Oregon State Univcrsity assumed IWO SIOTHficant. diffcr I ences to better model coastal storm conditions: breaking waves and rising wa.ter levels wtli time junor et al., 1999). In addition, Fiill-scale wall panels were [es[ed in as wa\le Lank to confii-in the theoretical results. The research PLIbliShCH irl 1999 Cound that walls constructed usirion- standard wood studs and StFLICLUI-al wood sheathin Lolled after being bit by several breaking waves avera-im, less than 2 feet I ri height. u. Those wave condifioris usually occur eartv ire coastal storins, when the stillwater depth is approximately 2 fi.,Iet above groUrld- AMIOU1111 the forces acting on walls are sio-nifi- cant, when the still-,vater depth is shallow the forces are expected to act close to Llie ground, Vdlel-C HILLCII Of HIC f0FCC is transferred into the ()I- to the I'Mindation near the ITFOLIFI(L Since loads experienced prior t.o failure of a proper-h- CleSiLY-11CCt and conStRICied breaka-way wall are applied near the bottorri of Hie Nv-all, forces transferred upwarri to the elevated build- ing are minimized. The tests On full-scale wall panels showed that vvood-frame breakaway walls [hat are designed to resist extrerne-wind conditions Will flail reliably at the connection between the bo,mom plate ofthe Nvall and the floor (see Figure 9). The tests showed that [he failLIFe begins with hownicy and gradual displacemetIL of the bouorn plate, or a similar secondary [Enlurc beuitiniiio- with the central suids of the breakawav- wall. The testing determined another secondary Enturc mode that can occur if the bottom plate of" the wvall does not break away. lit thIs case, with on1va slio-lit increase in a p p I I rd load, fa I I ure ivi I I occur at the connection between the botiorn plate of the o\'all and the bonorn ofcact'i wall stud (see Figure 10). The researchers concluded I'llat breakaWaV wvalls will ell"eciivo1v fail before the excessive loa.(L.s imposed by highev wave forces are transferred to the elevated building or foundation. ' Vhllc no Similar research on the performance ofsteel stuct-framcd breakaway Walls, CUI-FelltlV exists, tfiese typ(-.xs ofivalls are e\pecwd to fail in a rnanner similar t.o wood-Cramed bi'eAawav Wall lS. W'hlle no similar research lwaas I)CCII. U.n.dertaken to illustrate the PCH'OrInAlICC Of UIH-Cillforccd niasonry breakawav walls, these Types oFwalls arc expected to F-ail at the morutrjo ints between the till rel IIFO rced masonry emits. Faill-ire be near ihe stillwater- level where the pressure on the wall is aSSLITIled to be. (see Figure t I). t 0 Technical Bul l eTin 9 — auGuST 2008 Wave force Wave crest /,5+nmMm/mum wave height Stillwater Elevation Breakaway wall studs Vertical foundation member Exterior sheathing Failure of nails Exterior sheathing holding studs to bottom plate broken at bottom of breakaway wall C�� slab nailer plate Bottom plate Failure ofconnection between bottom of breakaway -� wall studs and breakaway waUbottom plate Teuhn|ua| Bu||oT|n 9—auGuST2008 Figmne8 Expected failure mode ofwood-framed breakaway wall based onfull- scale testing Figure 10.Secondary failure mode ofwood-framed breakaway wall aodetermined from full-scale testing Figure 11 Ma cted failur breakaway wall Verdcaa foundation member Wave crest �.• —Hollow Concrete masonry y' � minimum � units are ungrouted .5-toot wave height - Stillwater - J. elevation, ... r Breakaway wail constructed of -: unreinforced, hollow concrete masonry units Group rr=rrr % 3 _ , Concrete slab Acc orcling to Section 60. fie) (5) of the NFIP re rid ttiorrs, areas hc�lcaw elevated larrildinos in V -r.oncs rnav he Lnclosect in cabin of three wavy: with poorsulalaetrtiti ltreakaway avalls, tpert lat- t:ice-hock, or insect. screeriitra. The `l'Cla rcttlaticrrts SpeCitV that tattilclitzs ill V zc>rt s n-tt;tst resist ter the t°f1c°ct.s Ofc�ncl anddtiet- t.er toaCls rtc'.tMO, SIM1111,alicotisly oii all httilclittc, corrtlactnents (there al)lslicahte, seisntic lctacls rnttst also be acl(Iresse(,L). T'ltc 'TIP regttlatie>trs fl.rrther sl) ci€=, that breakav a-" walls anay hC clesigtie.cl anct corm trtrcted either: n With a desi�rr same loadhig resistance of not, less than 10 and not. more titan 20 la.sf, in which case special certification by a rc giste°r-cd design professional is not reclttirect. This ala- proach is described below as the Prescrilat:ive Design Method„ or n �Vith a dcsio-n safe loading: resiSLUI .e drat exce.ects 20 psf', pro -'Tided a reo-isrerecl design professio teal certifies that the dc°si0_n Meet's cc°rtain coriclitions. To hello the: design profes- sional certift- thc°se° coticlitions, two aplaroaches are, described helot v: a Sit 7l>lified Des-ir-rt Methcrcl and a Perf'Orn7ance-Based Des,i�n Ierho(I. 12 Technical Bul IeTin 9—auGuST2008 illiq Imm"Itim Arviiiii i Open lattice -work and insectscreening are not, considered to be walls or obstructions as long as thew will Collapse Ul-ldel- Wind and water loads without cattsing clarnage to the building. To increase the likelihood of collapse as intended, it is recorru-nended Llnu the ver6cal fram- ing i-fiembers (such as 2N4s) can which the screen or lattice -work is mounted he spaced at least 2 FC.Ct apart. Tidier- metal or symhetic mesh insect scrcctiiiig is acceptable, Wood and plastic hluiCe is available in -I-foot x 8-foot sheets. The material used to fabricate the lattice should be no thicker rha.ri V-, inch, and the finished sheet should have an opening ratio of at least 40 p . CrCeM. (AILI)OLLO-11 (-he regulations explicitly identify wood lattice, plastic lattice is acceptable provided it meets these recomt-riendatiotis.) ARhough not specified in the regulations, areas below elevated building may also be. u sr- roundedby plastic orwood shutters, slante([SlaLN, OF lOUVCPS {see Technical Bulletin 5). These ii-im-crials 1-11USL HICCL the f0llowinlu criteria: n Thev must be cosmetic in nature, n The material used For the slats inust be no thicker ihan I inch, and n Thew' mUS1 have an opening ratio of al. least. 40 percent. with a design saCe loading FCsiSLanCC of not less than 10 psf and not more than 20 psf are considered breaLuvav walls and dci not require special C-C111hCatioll I)V il VC11-iSU-Ted deSio-11 proFessiotial. This state ment It as caused it it ic I i confusion aniong d e%e I opci-s, designers, a n (I to - cat officials. The intent. is to allow flood loads acting oti breakaway walls to be neglected when designing the f(MuCtatiorl CICInems and the (.-.lcvaLc(L StrUCtU1'C itself'. It was never the intent to allow breakawa ' v walls LO be designed For wind and seismic p1-CSSLirCS that Ch-CumvC,11t or lessen local building or residential code requirements. The previoustv cited research showed that breakaway walls wifli a design safe loading resistance of riot more than 20 pst'Mll bail a i very low flood loads (i.e., 1.5-foot wave height). Thus, combining wave and wind loads on breakaway walls %VIL11 maxITIMIn loads acting on an elcNrated smicturc and foundation .system is, mireali-stic, MW not required v,,hen using the prescriptive design mediod. Breakaway W2111S that arc built in accordance vviLh the t6flowitilor prescriptive design method are considered t.o have a design sale loading resistance cif approximately 20 1-)sE Modern building and residential codes used along the GLI]f and Atlantic Coasts likely will require t,ml-'actorccl design wind pressures that exceed 20 psf". Building codes and material standards no loncrer perinit alloivable stress increases Cor rnason.rv, an.C.1 thus prohibit unreinfOrced masonry break- awav walls to he designed using this method.I I W�r� tip, The prescriptive design metho(I for wood-frarned and steel stud -framed breakawav walls does not require a design professional and is permiti,ed to be used if call of the Followill", conditions are satisfied: Technical Bu I I eTin 9 — a uGuST 2008 is 1. RrcakawaV Wall hC11111-11S are between 6 and 9 fecc, where piles, colurrins, or piers are spaced between 8 and 12 feet apart. (the, inethods shall he Lised for situations that fall OLILSidc Of LhCSC liffliLations). 2, The I-SCCA)FId gUS't desio-Ti wind speed does not exceed I I0 niph per ASCE 7-05 (see Ficylire 12) For all parts of breakawav walls, except those parts thaL are located �,viihin 4 feet of a building corner. Walls at building corners are subjected to siibstantially hitherwind loads. 3. t. exceed 100 The 3-second 1-u.St clesign ivind speed does no 0 niph per ,,kSCE 7-05 Cor those parts of brcakaway walk chat are located a,vithin 4 feet ol'a buildinIg corner. The NFIP does not require installation of flood open- ings (vents) in breakaway walls under buildings in V zones. However, a num- ber of State and local governments do require openings in breakaway walls. Check with the local building official or flood - plain administrator for local requirements. Technical Bulletin 1 provides guid- ance on flood openings. 4, The prescriptive design method is pen-nicied for all Seismic Design Catcgories identified in ASCE 1-05. 7 - brick vertecr or OLIXT maWlial LhaL niay be darnaged 5. Breakaway walls sery ng as backtup f6i 1 161) hV excessive deflections shall notbe desi-ned tising the prescriptive de.s1,,2,-n rnetho(L k'VOOd-11'tlMed bt,eakawav walls and steel stud-h-arned breaka,vav walls shall be coristi-Licied in accordance with Figures 13 and 1.4, respectively. A note in Figure 13 refers to Table 1, Table I is a seat: of' tables preserning alk![-HaLiVe Flail requirements. A note in Figure 14 refers to Ta- Me 2, which presents re.(jLT1Y"C'n1C11tS for sere-ws. friterpolation for differeiii, pile spacings and I I g wall heig-hts is perm fitted whell USUICT LheSC' tables. W)od-framed walls shall be constructed i,is- ing (Iood daniagt-resistant, No. 2 Grade Spi-tice-Pinc.-Fir Or hotter gradc,./species (e.g., No. 2 SOULFICI-11 Pine is be L,ter as defined by its higher allowable bending stres.si. Technical Bul I eTin 9 — auGuST 2008 1. 1 wi CL M Vl 2O 01 OM Cc u 0 v I M.0 0 2E 0-0 E x Cu 0 0 C 0 G -_8 > 2 0:2,zi Z,r: CI V, 7 Technical Bul I eTin 9 — auGuST 2008 15 Figure 13. Typical woo framed breakaway wall construction (prescriptiv method) I /Exterior 7 \-2-16d Toe nails (typical) framing Table 1 aTotal required number of galvanized common nails (divided equally between top and bottom) for wood-frarned breakaway wall configurations with 8-foot pile spacing Table 1 b. Total required number of galvanized common nails (divided equally between top and bottom and evenly spaced) for wood -framed breakaway wall configurations with 10-foot pile spacing Table 1c. Total required number of galvanized common flails (divided equally between top and bottom and evenly spaced) for wood -framed breakaway wall configurations with 12-foot pile spacing i6 TeoUn|om| Bu||*Tin 9—aoGu8T2008 Beam Permanent 2 x 4 nailer 4-inch wide w utility blockout Breakaway 362S1 62-33 /Exterior at 24 inches o.c. sheathing 7 Screws per Table 2 2 No. 6 screws (typical) Gap — Built-up Breakawav 362T 150-27 framing Permanent 2 x 4 nailer B u I I eTi n 9 — a u Gu ST 2008 17 M�� Figure 14. Typical steel stud -framed breakaway wall construction (prescriptive method) .All hveakawav walls designed nsing the py-escriptive design inet.hod shall be detailed ill ACCOr- dance with the f"ollowill1g: I , Fl)reakawav �vatls shall he de.siI,,).,-ned to nicer all, applicable local requii-enients and bLiltding code requit,enients. 9� As shoo In FloTiLi-es 1,3 and 14, wood-ftarncd and steel sn_icl-fi-anied bueakawav wall panels shall not be attached to the pilings or other vertical fotindation ineint)ei-s, Only- the tops and bottonis 4wall panels shall tw connectcd to pet-nianeric 2x4 nailer places. 114')Oi-capac- M, conricctoiS SLIC11 as bOILS, hig' SCI-CIVs, nietal straps, oi- hi-n-ricane fasteners (e.g., clips or straps) shall not be i-ised. Technical Table 2. Total required number of No. 6 self tapping screws (dded equally between top and bottom and evenly spaced) conforming to SAE J7'8 with a Type 11 coating in accordance with ASTM B 633 for steel -stud framed breakaway wall configurations M�� Figure 14. Typical steel stud -framed breakaway wall construction (prescriptive method) .All hveakawav walls designed nsing the py-escriptive design inet.hod shall be detailed ill ACCOr- dance with the f"ollowill1g: I , Fl)reakawav �vatls shall he de.siI,,).,-ned to nicer all, applicable local requii-enients and bLiltding code requit,enients. 9� As shoo In FloTiLi-es 1,3 and 14, wood-ftarncd and steel sn_icl-fi-anied bueakawav wall panels shall not be attached to the pilings or other vertical fotindation ineint)ei-s, Only- the tops and bottonis 4wall panels shall tw connectcd to pet-nianeric 2x4 nailer places. 114')Oi-capac- M, conricctoiS SLIC11 as bOILS, hig' SCI-CIVs, nietal straps, oi- hi-n-ricane fasteners (e.g., clips or straps) shall not be i-ised. Technical Table 2. Total required number of No. 6 self tapping screws (dded equally between top and bottom and evenly spaced) conforming to SAE J7'8 with a Type 11 coating in accordance with ASTM B 633 for steel -stud framed breakaway wall configurations `1. The exterior sheathino- on breaka,,vav wall panels shall neither overlap nor be attached to the vertical foundation members. 4. Breakaway wall slicadling and siding shall be disc on tin no us at elevated floor beams and joist..s; horizontal separanon joints shall be provided to prevent damage to the sheathing or siding above the floor of the elevated building (SCC Figure 5). As shO\,VTI in FiO7Ul-e 15, a watertight seal shall be provided for separaLionjoints to prevent i6nd-driven raiti water and sea Spray from entering the building envelope. A similar vertical seated joint may he needed in front of the piling. 5. Udlibes, i I I Cludi I ic-relectrical wHing, breaker boxes, I)OWCU In CLCI-S, PIUMI)i I Ig, condilits, arid ventilation ducts, shall not he placed in or attached to breakawaywall panels. Buildingsupply 1111CS MId OL11cr- Utfl1LV fiVILI-CS, Such. as HAL switches air elecrrical outlets, may be attached to the sheltered side of vertical fOLIndallon members as alknved bv applicable building; codes and floodplam management regulations (which generally require th�-ir utilities be elevated above dic, BFE). If Litility lines nH,.L1;t be FOUIC(l into or out, of air enclosure, one or more of* the walls shall be Cons[ ILICLed wl[h a UfflitV b1C)CkOL11 (Set,' Fio-U.FeS B and 14). Utilll-v lines tIML Pass [11FOUgh the blockour shall he independent of. the wills and therefore will riot he damalged if the wall pariels break awa�, 6. Breaka%aN,tall p',i.iie.1s,-,Iiatllbcpositioned SLICIlthat, otif�iilLti-e,i.lie- ' v do not. collal.-)se against, cross-braCing of Lhreaten other foundation coinponents, (for niore information, see'lechrii- Cal Bulletin 5). 7. Partial height breaLIWIV Wall systems are not. permitted, 1 -, Problem: Design as I 040ot wide by 940ox Call wood -Framed breakaway wall for as ')-second (YUSL desilgri wind speed of 1. U.) nil,-)I-i. The Scismic Desilgil Calcgon, is D, deflec.tion, of the wall is riot u-rtj.,)orLarlt, and the wall is not within 4 feet Ofa, buildincy- corner. kVood frarnino- shall be con- su-ticted using flood darnage-resistant, No. 2 Grade Spruce -Pine -Fir 2x4s. Solution: The problem description clearly altmvS Lhe Use of the prescriptive design method. Figure 13 shows that. 2x4 SLLAds at 24, inches k)n Center (o.c..) shall be Me nailed to the L.Op and Ix, )ttom phttes I..1sing tN-vo l6d nails. According toTadble 1h. iwent-,-I'Our 10d nails (12 top arid 12 hortorn) can he used, to connect the brcakaW�LV tole arict bolton-i plates to perrnarient 2x4 nailff plates. In most coastal areas, the adopted bUildinIg codes include wind and,'/or seismic design require- ments that. exceed the 20 pst' maximilin limit allowed for breakawa,,- walls that. do not. reqUlfc Certification by as r-c—istered, design professional. NFIP perl"OVITIMICC criteria also allow for de- signs that, meet these higher load reqUirenients. Breakaway teralls wnh alloNvabl(, loads higher than 20 psfare permitted if as designer Certifies that ( ) the wall will collapse before base flood couditions are reached, and (2) the elevated tmilding v611 not he damaged by corrrlairred wind. and flood loads acting on all building components. t 8 Technical Bul I eTin 9 — auGuST 2008 House walls a nd Sealed separation joint Figure 15. Separation joint between sheathing and wall covering (e.., stucco, siding) on house walls and breakaway walls Breakaway walls designed ill ac�c'orAitl-lce Wit}1 ffie simplil ccl desi€ ri nietliocl will have a cle- Slgll SaCC lrrrtrlirr;; r-esistar�ce that cxc ec(ls ` 0 psE The l�rcVicnrsl�' eitect research sliowecl t:li at. wave loa(ls crra eletatccl smict.tires are rrrirrirarizecl ifbreakawa<� walls are clesi(;rred to resist, wir°icl. loads LIP to 55 psi. Tli re(`crr'r.. walls;clesil-trect rrsitrl; [tie sirripli(7eci clesi�rr rrretlrca(l meet '_'�FIP performance critcria. SULA, mail, artd screw a �cgUirerT1CrIts pIrCSeY t€rct ill tlziS SeCtiOrl meet the str-irilgetit clesilc rr coiWitiotis ctesc.ril�ecl l)elr�t+� Land. rrtat� l)e relaxecl as lcstig as the clesil;�rre°t- Technical BulleTin 9—auGuST2008 19 ensures that the breakawav wall satisfies the vo\ernin- code's wind and:/or scisrnic require - In CDLS. Future research acid testing (..)ii wal Is with design wiridpressi-ires significantIvexceeding 55 psfmay allow use of the sirnplified method wvhere the 3-second gust design wind speed ex- ceeds 140 rnph. Z== The slinplified design inethod fOr wood-franied and steel StUd-fl-aHIC(I brcakawa�° walls (toes not require a design professional and is pernill-ted to be Used il'all Of the U)1101villcr Conditions are satisficcl: 1. Breakaway wall fieli0its are between 6 and 9 fecu- where piles, colun-ins or piers are spaced between 8 and 12 feet apart (the perforniance-based method shall be used fOF situations that tall OULSIde of'these 111-nitat,lons). 2. The 3-second gust design ivind speed is bet-,vecri 110 and 1.10 niph (see FicrUre 12), The simplified design rnethod is permitted foi- all Scisinic Design Catco-oriel identified in ASCE 7-05. L Breakawav walls serving as backup for brick veneer or- either material that max- be daina,yed bv excessive deflections shall not be CICSig][CCI USilJ(1_ the simplified design ined.iod. N;Vo(A-Framcd walls shall be COnStl_UCLCd USIflg 1100d darriage- resistant, Spruce -Pine -Fir or better species (e.1., Southern Pine is a better species as defined by its hil-her allowal-fle bending St.ress). Wood-fi'anied br-eakaway walls and Steel stud-f-l-'ayne.d breakawav wvalls shall be c(.)nStVUCLC([ in accordance with Fi,,),- Ul-C'S 16 and 17, respecti\el,, (notes In Filg,ui-c 16 refer to Tables 3 and 4, and notes in Fiallr(' 17 I-eftT to Jables 5 ancl 1 Tables 3a, ' 3 b, and 'c provide required stud spacial; for Stud Grade, Covisrruction Grade, and No. 2 C-rade studs as a function of'Nvind speed and wall heilght. Stud spacing val- Lies niav not be interpolated (e.g., Use 120-niph design kvind speed ifactual desl'gii wind speed is greater- than 11( inph, but less than 120 rnpli). Tables 4a-, 41), 4c, and 4d provide the total required nu.1-riber ()f- nails I -or dif-ferent design ivind speeds als a function of -wall height and pile spacing (interpolation is allowed). n 'Eible 5 provides 1e(jUirCd SpaCill(I f'()I- Steel studs as a [in -lc - lion of wind speed and wall hC1ghL_ Stud spacing values rnav not. be interpolated (e.g., use I 20-niph design wind Speed if' 1 actual desig-li wind speed is grCaLCU dlMl I LO niph, but less than 120 mph). Figure 16 shows that 3 - 16d toe nails are required for all cases. Although no specific pattern for toe nailing is required in this Technical Bulletin, the National Design Specification for Wood Construction requires that edge distances, end dis- tances, and spacings be sufficient to prevent splitting of the wood. If horizontal construction is preferred by the contractor, 1 - 1 6d nail installed end grain to the Stud can be used with 2 - 16d toe nails installed in alternate directions once the wall is placed vertically (see Figure 16). Likewise, 2 - 40d nails installed end grain to the stud can be used so that the breakaway wall can be assembled hori- zontally and then nailed in place to the permanent top and bottom nailer plates. It should be noted that pre - drilling may be required in some cases, 20 Technical Sul I eTin 9 - auGuST 2008 n Tables 6a, 6b, Gc, and 6d provide the required nurriber of'self Lapping screws for differ- ent design wind speeds as a function ol' wall helghr and pile spacinig (Interpolation is a] I oxved) . Careft,Ll plan review and inspection by local Jurisdictions is parairrourit when the simplified design method is used. Plan reviewers inusL ensure that the proper nurnber and type cif- con- nectors, are specified Lor both the cop and the bottorn plate connections, and inspectors should pay close at Len tion that the insLalkiLion complies with the approved plans. Ira arc.as whet-c design wirid speeds are less than or equal to 140 inph, inspectors niaV accept triore top and botioin connectors than are specified in Table 4 (L'Or wood studs) and Table 6 (f'(-.)r steel stuck).o ' However, because breakaway wallsu Fall near the grorid, it is Irriportairt that the. ritunber ot'boliom plate conriccLors riot exceed one or Lwo more than the Munber ot'c(-)n- nectors specified in Table 4d and Table 6d (regardless of(lesign wind speed), or per-forrnance will heJeopardized. Design details clescribed FOr the prescriptive dcsl,,,ii nied-rod in the PrCVIOUS SC(:,Li(,)Il apply for the simplified des] re method (see page 17) Beam Permanent 2 x 4 nailer 4-inch wide utility black out B reakaway 2 x 4 Z (spadng per Table 3) v, Exterior sheathing N S- ap Figure 16. Typical wood - framed breakaway wall construction (simplified method) Table 3a. Required 2x4 stud spacing (inches) for different design wind speeds (mph) and wood -framed breakaway wall heights (Stud Grade) Table 3b. Required 2x4 stud spacing (inches) for different design wind speeds (mph) and wood -framed breIakaway wall heights (Construction Grade) Table X Required 2A stud spacing (inches) for different design wind speeds (mph) and wood-frarned breakaway wall heights (No. 2 Grade) 11 111111311111TERMTHUMMM HE 11� 11!! 1 pil III Table 4b. Total required number of I Od galvanized common nails (divided equally between top and bottom ant evenly spaced) for wood -framed breakaway wall configurations (design wind speed = 120 mph) Breakaway Wall Height (feet) --F-- 6 7 8 9 Nails Required for 8-foot Pile Spacing 20 22 26 30 Nails Required for 1 0-foot Pile Spacing . . . . . ...... 24 28 32 ju Nails Required for 12-foot Pile Spacing 30 34 38 44 9 9 Technical Bul I eTin 9 — auGuST 2008 Figune17. Typical steel stud -framed breakaway wall construction (simplified method) 4-inch vvide utility bioclkout Breakaway 362S162-33 (spacing per Table 5) Exterior sheathing \—Screws per Table 6 \_2 No. 6 screws Built-up Breakaway 362TI 50-27 framing Table 5. Required 362S162-33 stud spacing for different design wind speeds (mph) and steel stud -framed Technical Bu||eTin 9—aoGmGT2008 2 �', !able 6a. Total required number of flo. 6 self tapping screws (divided eq�ually between top and bottom and evenly spaced) conforming to SAE J78 with a Type 11 coating in accordance with ASTM B 633 for steel -stud framed breakaway wall configurations (design wind speed = 110 mph) Tab;le 6b. Total required number of No. 6 self tapping screws (divided equally between top and bottom and evenly spaced) conforming to SAE J78 with a Type 11 coating in accordance with ASTM B 633 for steel -stud framed breakaway wall configurations (design wind speed = 120 mph) Breakaway Wall Height (feet) 6 7 8 9 Screws Required for 8-foot Pile Spacing 34 40 46 50 Screws Required for 1 0-foot Pile Spacing 42 50 56 64 Screws Required for 12-foot Pile Spacing so 60 68 76 —a," 10 m lilt !! i e T Tapping screws olviaea equally e ween Top an Do om anff- evenly spaced) conforming to SAE J78 with a Type 11 coating in accordance with ASTM B 633 foud framed breakaway wall configurations (design wind speed = 130 mph) Table 6d, Total required number of No. 6 self tapping screws (divided equally between top and bottom and evenly spaced) conforming to SAE J78 with a Type 11 coating in accordance with ASTM B 633 for steel -stud framed breakaway wall configurations (design wind speed = 140 mph) Probleni Desio-ti a I O-Coot xvide hv 94'oot [all ivoo(].-Frai-iie(l bi-eakawav wall I'M- a 3-secouct vust des](YII NAIncl spced of' I 3W inph. The Sc,,isniic Desio-Ti is D. dcIFICCLion of the wall is not, inipoi-tanL, and the wall is xvithiii 4 feet oil 1-.nii1cling czar nee iVoo(l fi-an-tlrig- shall be cotisLY-110- C(I LISH-W floo([ damage-i-esisi:aiii No. 2 Gi7acle Sprtt(.-c-Piii(,,,-Fii-, SOIL111011: The pt-()blem clesci-ipilon cleat-ly allo,vs the t.ise of' ttie siiyiplified clesigri i-yietl-ioct. .�CcOrdfl-ig to Table - ic, 2x4 stucts at 12 iii. ox. shall be toe nailed to breakawa,,,, 2x-4 Lop and boLtoin plaLes ushior three 1%5d iiails ([rani Fiulu-e 16). Accor(Jing Lo 'Fable 4c, f0voLwo 10(l iialls (21 Lop aii(t 21. hot.[oiii) shall bc� t,isccl Lo cormect clic bi-cakawaY top aucl bottoril plates to per-iiiarie.iit 2x4 hailer plates. 2,4- Technical Sul I eTin 9 — auGuST 2008 As explained in the section on design metliodolog, (see page 21), because this example is in an area wiffi a design T6nd speed of less than or equal to 140 mph, additional top and bot- torn comieciors may be LISCd and accepted by inspectors. However, to allow the wall to break away as intended, inspectors should 110L accept more than the number of hott.om cnrinecLOFS specified In Table 4d (plus an additional one or LAvo). Therefore, while the solution indicated by Table 4c requires 21 nails at the cop plate and 21 nails at the botiom plate, the maxIML1.111 number that inspectors should accept for the bottom plate is 26, nails (per Table 4d, 24 nails PtU.s not more than rAvo extra nails). Breakawav walls desicnied in accordance with the perf'ormance-based design rneLhod will nor- i!) "n rriallv have art allowable load of' more than 20 psf. Flood loads (i.e., wave loads, h)drodvilainic loads, and impact loads) on breakaway Walls 11ILLSt be calculated and taken into acCOL1111 WheH Clesi("Ifill", the elevated St'ruclure and the fomidation system. HmAvver as described below, tile I I designer is given stighLh move fi-ecdom when detailing breakaway wall systems. MF.U= PCrf()l_TTlal_lCC-baSC.d (IC.Sigil of breakaway walls crust be 1-.m-fornied bv a design professional. This method is always permitted and these walls may be designed and CoCtSITLIC[Cd LIS1110- wood SLUAS, Steel-StUdS, U111-Cillf'Orced masonry, or alierriahve materials. However, it is anticipated that perforniance-based desillyri will be used primarily Shen the applicability criteria (e.g., t,aflrr walls, wider spa,trs, Ill"lu'r desl,-11 wind speeds) for the prescriptive and simplified design methods, cannot be satisfied. MMEMMM= Ile rform aii ce-based design of -breakaway walls consists of desigritrig the by-cakawa.v wall tar resist the, largest out.-of-planc load of' {Ia) the CICSigrl Willd 131-CSSUI-C in rCC0r(hUlCC with ASCE 71-05, (b) the desi<7Yn seismic otti-of-plane [()ad in accordance with ASCF. 7-05, or (C) 10 psi'. A1111OUgh breakaiva 'v walls are pertriMcd by NNIP re1vulat,ions, tile effects of flood loads oil these, walls (and ariv other buildinla components thatare below the BFF) must, be included in the design of the elevated structure and its foundation. It should he rioted chat more resistant breakawav walls increase the potential forces from debt -is impact, loading on Foundation elements and possibly mi nelghhoi-11111- StFUCLUAVS. ilk - >« �11= All breakaway walls designed using the performance -haled design i-TreLhod shill be detailed in accordance with the follm"ArICY: L Brcakawak- walls shall he designed to ryiect all applicable local requirements and building code requirements. 2. Breakaway tNTall sheathing and siding shall be djSCOnLiRUOUs at elevated, floor beams and .joist.s, horizontal separationjoints shall be provided to prevent damage to the sheathing or siding above the floor of the elevated building (see Ficrure 5) . As shown in Figure 1,55, -tall be provided for separation joint's to 1)1-cv(!l I 'ven rain a wmertiaht seal A it w'rid-drivers ill waLer I Technical Bul I eTin 9 - auGuST 2008 25 and sea spray f'rorri enWr'illcy- the building envelope. A similar vertical sealedjoh-it nia".- be needed in front. of the piling). Utilities, including electrical wiring, breaker boxes, Power meters, plumbing, conclUnS, arid ventilation ducts, shall not be placed in OFattached to breakawavwall panels, Buildinustippk lines and Other Utili[V 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 0 and 1k.)odplain management regulations (which generally require thatt utilities be elevated above the BFE). If'Littlity lines must be routed into or out of' an enclosure, one or more of the walls shall be constructed with a litilit.il bloc.kout (se.e. Figures 13 and 14). Utility lines that pass through the blockOUtshall be independent of the walls and therefore will not be damaged if the wall panels break away. 4. Breakawavlvall panels shall be positioned such that. Oil fallUl-C, Lhvv do not, collapse against cross-I-.)raiciiigot-Ll'ir-eaten otherl"OLInciation component-s ffori-nore fiffori-nation, see Techni- cal Bulletin 7 1 I Partial heighi breakaway wall systems are not permitted. k\lien using the perf"ormance-based design method, wood-fl-arried and steel snid-fi-amed br-eakaway wall panels may be attached [o pilings or- other verticalt. fomdation members (i.e., all four sides ot'the pane( may be attached) as accountf�ed or in the design of' the wall and foundation elements. ITti t-e'Ill I* OFCed, Ull-FOLAC(l 11011OW-Ce,11 I'llaSO111-V UrilLS inav be attached to floor beams and to concrete or masonry vertical FOUndation members with standard n-iortars and Ininin-ItIM I)C- rirrieler connections, as accounted For Ili (he design of the, wall and f'Ounclation elements, COMMUOUS breakakvay wall systenis rliaLspan across pilings arc not permitted. mrimmm= The NFIP requirerrit-nis For breakawe �-Iiv walls have direct, Impacts oil Ili(' other building- ele- ments described ill this section. Umm- Utilities and attendant eqUil-MIC11tshall not be mounted on, pass thr(A10-11, or be located along breakawaV walls. XVhere utilities and attendant equipment. (e.g., lightirlo, Circuits, switches, re- ceptacles) are required to be Installed below the BFF. to address life saf'etv all([ electric code requirenients, they shall be 1-TIOUnted on the sheltered (i.e., landward) side of founclation I'llernbel-S. lf'LUllnNT llrleS must be routed into or out of' an enclosure, out,, or more ol'the avalls shall be constructed with a utility blockollt. Utilit,, lines that pass through the blockoUL Sht111 be independent of the walls and thercf'Orc will not be damaged ilk the wall panels break awat. Garage Doors Garage doors installed in enclosures with breaLOvay walls are not exempt from the NFIP mre- ential garage doors ma%.� be quireents to break a�, H awunder (food conditions. SLandai-d I residI 26 Technical Bul I eTin 9 — auGuST 2008 considered breakaway panels and flood loads aWtiflu Oil these doors need not be considered Although such doors have not been tested under wave loads, the IRCrequires tire USC of doors I that have been tested for- wind loads. Experietice has shown that these doors fail under vets - low wave loading that. will not SignifiCaudy affect the elevated home (IF foundation. Garaue doors rnav be desion-tied and detailed using the perf'Orniance-based design provisions described in this Technical Bulletin, Partial -height breakaway walls do nor satisfy the NFTP requirements and are not permitted. These walls are constructed so that the bottom portion of the wall breaks away while Lhe Lop porboti of the wall (above the BFE but belOW tile elevated structure) is Siren ,' ) 3 -thel-led to SUI-VI'Ve, the desiffn event. The NFIP reOldacionsspecifically state that walls below the lowest floor Ofan zl� 1-7 elevated building shall be breaka,,vav walls. Emmmum; Exterior facade treatments such as brick veneer, concrete plank, Stucco, OF other Unrein- forced nonStrUCLUral elements ruav be attached to hreakawav walls provided the facade does FIOLinhibit the breakaway characterisucs of, the walls. Facade comiections shall be desio-ned tend detailed to meet huildiiig code requirerrients for wind and seismic loading. Iforizotital separationjoirirs shall be used at tire elevated t1oor level to mimmizc damage: to the elevated structure. Eticlosures below elevated bUilditi-s are allowed only for parkirig of'velticles, bitildincy access, or, storage. Tris[allinIg utility stub -outs (i.e,., purposely placed utilit, access points for future cotinecdoris) is incmisisterit with Lhc a]l0WabIC uses Ofan unfinished enclosed area. Likewise, firushim- the interior ofenclosures with drywall or other firiish materiails is not permitted un- less FCCILLired to address life-safet-, and fire code requirements. Ari exception exists fear- steel stud -framed breaLkaivav walls, where structural perl'ormance tinder- wind loads requires con- LinUOUS laterat bracing of` both stud flanges. The NFIP requires t.hat coust.ruction materials used below the BFE be resistant to flood dam- age. Flood darnage-resistant rriaterials are those that M-C capable ofwithstariding direct and prolonged contact (i.c., at least 7/2 hours) With floodi,waters iVit.hOLIt SLIf[ering sign fficant darri- ac,e (i.e., dama7)e requiring more than reasoriable clelt ear low-cost cosmetic repair, such g Lis paint rig). More details are foutid in Technical BLIllctiri 2, Flood Dar age-Resistarit Materials Requirements for Buildings Located in Special Flood Hazard Areas. Unless other materials are required t<t address life Saf'CLy and fire code requirements, flood darimig-e-resistaiiI materials shall he USCd for breakaway walls and wall panels, as outlined be - I mv. Technical BuP I eTin 9 - auGuST 2008 `a-1 Wood -Frame Materials n All lumber shall be preservatiVe-treated or decmresistant (e.g., redwood, cedar, some oaks, and bald cvPress) n Exterior siding shall be cxterior grade and no thicket- than V--inch plywood, M3,-k 32 /16 rated ,sheathing or other equivalent sheadiln", material. n Will studs shall be no larger than 2 Niches x4 inches (nominal dimensions) unless designed using the performance -based design provisions described in this Technical Bulletin. n Interior wall sheathing- shall not be permitted. Metal Connectors n Metal connectors shall be corrosion -resistant, (see Technical Bulletin 8, Corrosion Protection for Metal Connectors in Coastal Areas). Other Materials n Light -gauge fi-arnino-, such as steel studs, shall be coated to resist corrosion. ;-) t7 11� n Stucco, Exterior InSUlation Finishing Svl,,Lcnj (EIFS) rNralls, and other lil-hinveight exLerlOr sheathing material may be applied, as long as a separation Joint, is provided where the irnuerial is attached at or ricar the bottom of the clevatcd floor be am or 'joists (see Filcy- tire 15). Insulation shall also be installed with a separation joint so LIKIL It does not hinder performance. n Foarn sheathed walls may he designed and used as breakawav walls in accordance with [he performance -Based desilgii provisions presented in this 'FechniCal Bulletin. Work that is (Ictcri-nined to be substantial improvement of an CXISUFIg building (including additions and repairs ofsuhsiannal darriage) must c(.)mplV With the NFIP regulations and the entire structure must also be brought into compliance. �,Nork on any existing building diat tVas constructed in compliance with the NFIP requirciTICUILs rnLISI. C0111PIV With the requirements and not jeopardize the continued compliance of' the building. Theref"Orc, if enclosures are added belOW COITIlDliant I)Uildfligs, breakawaNwalls shall he used. For more inforniation �Lbotlt reqUircnients far substantially improved and substantially darnaged buildings, see Ans-wers to Questions AbOLIt Substantially Darnaged Buildings (FENIA 21 )). HJURiTIT111 =5 FENL.,Vs NIAT reports consistently show that buildings in areas mapped as AE zones and sub- ject to tidal flooding, wave forces, scour, and debris impacts often are severely darnagcd. The landward boundai7- of the V zone is where the depth of Nvaier can no longer support a 3-Boot. breaking A zones are mapped inland Of' the V zone to the landward boundary of the SFHA. Figure l8shows older horrics located in a mapped AE zone that. may have sustained significant flood damage caused by debris impact resulting front inundation and waves. Figure 19 shows 28 Technical Bu I I eT n 9 — a u GuST 2008 a strLicti-ire in an AE zone chat was elevated above the BFE, where the enclosi-ire's breakaway walls performed as intended, Widlot,it daniage to the elevated sti-licnire. Portions of the AE zone areas whcre wave -related darnao-e occurs have been cle(ermined to be areas where the depth of flooding can support waves bct-%ween 1.5 and 33 feet high (which Only i-equires approxin-iately 2 feet of water depth). These areas are called Coastal A Zones (CAZs). Historically, (:,.-kZs have not been delineated on FIRMs, although sorrie coli-lintififties are delineating then-i or are reclLWSLIng that the delineation be providedas an int-orniacional layer ww,hcn FERIA 1:)rodLtCCS 11C.1V diOjLll FIRMs. �fl-iere the infori-naLional laver is provided by FEMA on coastal neap studies, the boundary line is called the L.itnit ol"Moderates NNave Action (Ll-NnVA). FEND scrona-tv reconirnends that structures in C,,Vs be designed and consti-l-icted to meet71 , V Zone requirements, including reqwrernenLS for breakaway walls- How ,ever, the NFIP regula- tions also reqtiire flood openings in walls snri-ounding enclosures below cle.vated btfildin-s in CAZs (see Technical BLII]Ctill 1, Openings in FOUndation Wallsand Walls of EnCIOSLINS). Brea.kaWaV walls Lised in C.AZs rni-ist have flood openings that allow for the automatic eijLn- and eXA of floo(hvaters to mirimr-liz.c. damage caused by hydrostatic loads. Openings also fitnCtiorl dLfflinu smaller-moans(.)I- if` anticipated wave loading does not occur with the base flood. Figure 18. Homes in AE zone devastated by wave forces and debris Technical Sul I eTin 9 — auGuST 2008 29 Figure 19. Structure elevated above BFE in AE zone, showing successful response of breakaway wail's The U.S. Cmi(yress estaahlished the NFTP with the passa e of the National Flood Insuraance ;-act of t.968. The 7FIP is as Federal prograni enalal at;; property owners in participathi coin- rnunnres to purchase ni.surtance as proLection at air1st flood losses, in exchange for Sttat.e and corm-nuniv, lloodplaain rnanagement reattlations that reduce future flood daamaiges. T'arncipa- titan in the NFI' is teased on an agreernent betEaeen corm -aunt ties and the. Federal Government. Tf as cormnunity aadopts and enf )rces adequate Hoodplain inana,ean I L re-ulatioIas, FFNfA t ill make flood 1,11stcrartcc. aava lahle mtlaitr the; corninintitV, Title I f ofthe U.S, Code ofederal Regulations contains the NF[P criteria for lloodplaira Man- agement, including desimt and corastratction standards for new and stahstaratiaally improved huildim)-s located in SFIIAs, identified on the NF P's FIR -Ms. FI::MA encourages cornrntanities to adopt floodplain nianageineni regulations that cxceed the ininitnt.ana NFIP criteria. As an instarance alternative to disaster assistance, the NFIP reditces the e.scalatin costs of repairin ; damage to ht. ldinlgs acid their, contents caused by floods. This is one of at series o ' Technical I3talletins that FEMA has produced to provide guidance concerning the huilding per-Comaance rerpuiretnerits of the NFIl?. These requirements are con- tained in Title 44 ofthe U.S. Code of Federal Regtilaations at Section 60.3. The hatlletins are intended for ttse by {hate and local officials responsihle For interpretin and enforcino. the recpatirc°raterat:s in then- floodplain management reptlatticans and httildinf; codes, and by mere- hers of the development community, such as design professionalsand huildera. New bulletins, as well as updates of c sisong btillctirls, are isst:ted p)eriodicatll , as necessary. The bulletins do not create regulations, rather, they provide specific giiidance for, cornplyin- with the require- merits of existing NFIP re tuitions. Users of the Technical Bulletins who need additional ;30 Technical Bul i eTin 9 — auGuST 2008 guidance should contact iheirNFIP State Coordinator orthe appropi-laic FEMA regional office, FEND,'s User's Guide to Technical BLIfletiris lists the bulletins issued to date. �M_I! The quickest, and easiest wav to acquire copies of FENIA's Technical Bulletins is to down- load, thern from the FEMA website shnn). Technical Bulletins also may be ordered free of charge from the FENIA Publications �Varc- house by calling 1-800-480-2520, or by faxing a request to 301-3162-5355, Monday through Friday bevveen 8 a.m. and 5 p,ni. E.ST Please pr(,.)vicle the FENIA publication rILLMI)CF, title, and quantity- of coach publication requested, along iNiLh your name, address, zip code, and day- time telephone number. Written requests i-nay be also be submitted by mail to the followinu address: FENI.k Publications P.O. Box 2012 .Jessup, NIII 20794 The sources provide further information concerning breakaway walls below elevat- ed coastal buildings. American Forest 9-- Paper Ass(..)(:iatioril/Airieric<iii `rVood Council, 2005, NDS: National Desipi Speci cation for Wood Construction. Anierican Society of Civil Engineers, StfULCILtral Erigincerivig 111SLItUtC. 2005. Flood Resistant Design and Coiistruction, AS(.,'E 2r,l-()5. Airicrican Society (&Civil Engineers, Structural Engineering Institute. 2005. MiriirrlUrri Design Loads for Buildings and Other Structures, ASCT. 7-05. FENLA. L991. Answers to QUestiotis About Substantially Damaged Buildings. FENfA 213. FENIA. 2000. Coastal Construction Manual, FENIA 55CD (3rd edlL.10[1). FE'NLV 2005. FEM,k 499Home Builder's GUideto Coastal ConstrUctiori Ter-hii ical Fact Slieet Series. FENUV 2008. NFIP Technical Bulletin 1-08. Operiiiigs in Foundation Walls and Walls of Enclo- SLINS. Technical Bu I I eTjn 9 - a uGuST 2008 31 FE A. 2008. N;FIP Technical Bttlletin 2-08. Flood Damage -Resistant Materials RCquirenents. FEMA. 2008. NFIP Technical BLdletin 5-08. Free-rf-bstruction requirements, FEXIA. 1996. NFIP Technical Bulletin S-JCS. Corrosion Protection for Metal Connectors in Coastal Areas. International Code Council, fire., 2006. International BuildingCodeCD, IBC 2006. International Code C otinc:il, Inc.. 2006. International Residential Cod6D, IRC 2()06. Rogers, Spencer M. 1991. Foundations and. Breakaway Walls of Small Coastal Buildings in Hurri- cane I -Ingo. Proceedings of Coastal Zane `91. American Socie t� of' Civil Engineers. New York, NY Tmio , C.C...: Fga:. hunial Kasai; Spencer I. Rogers, jr.; S.C.. `r'f°la. 1999. Behavior of Breakaway Wall Subjected to Wave Forte: Analytical and Experimental Studies, north Carolina Sea Grant, North Carolina State: Universi,tv. alcigh. NC,. Base ood — The flaxad having a I- percent chance, ofbeing equaled or exceeded d in arrr given tear; commonly referred to as the " 00-�'CW' flood." The hzasc flood is the, national standard Used lry the NFIP and all Federal agencies for the purposes of' ritluirirag the purchase of flood insttrance and regulating neiv development. Base ood elevation (BFE) — The height of -the hale (1- percent .annual chance or 100gear) flood in relation to the specified datttrrr oar the. c.ornm arr ty's flood hazard nrap, Usually the: National ( odetic Vertical Daw.rn of 1929 (:MCVD), or t:he'North ,Vrier-icari Vertical Datum of 1988 (NAVD). Breakaway wall — A wall that is not part of' the strrtctnral support ofthe building and is M- tended through its design arrc[ coatstrarction to collapse under, specified lateral loading forces, Without causing damage to the elevated portion of the building or supporting f'oundat.ion sys- tell]. . Coastal A Zone — An area witlmi a special flood hazard area, landward oC {a V zone or land- ck,<ard of an open coast r,it r.ont mapped V zones; in a Coastal A Zone, the principal source OF flooding rnarst be astronomical tides, stoa-rra starges, se iches, or tsttnzamis, not riverine flooding. DUI-ing tht base flood conditions, the potential for Evave~ Ineights shall he greater than or egUal to 1.5 feet.. Coastal 1. Zones are not. ate>r-really dc,signatcd on FIR7\4s. Coastal H igh Hazard Area —An area of special flood hazard extending from offshore to the inland limit ol'a prinimw frontal dtane along an open coast and any other caa-ea suhje:ct to higrh- veloc:ity save action f ore stornns Or scisrnic sc:>urces. 3`?' Technical Bui I eTin 9 — auGuST 2008 Detailing — The desiun practice Of using; structural and architectural drawings and specifica- tions to arrange, confiultre, and connect StrUCLUral and. 11011SLI-LICLUral btillding components of a building system. Design details convey to the contractor exactIv how the structural and nonstructural components of a building should. be built. In Federal Emergency Management Agency (FEMA) — The Federal agency that, in addition to Z:� 11� carrvina out other acm.uics, administers the National Flood Insurance Pro � 1� 0urarn. Flood 111SUrance Rate Map (FIRM) —The official reap OF a comn-uunity on which FEMA has delineated both the Special Flood Hazard Areas (SFHAs) and the risk prernium zones apph- cable to the coaununi[V. I Hydrodynamic load — The load imposed on an immersed object, such as a foundation element or enclosure wall, by water flowing against and aFOU11CI it. The Magnitude of the hy- drodynarnic load varies as a function ol"velocity and other factors. Hvdrostatic load — The load imposed on an immersed object such as an enclosure wall, by standina or slowly movinawater. The magnit-Licle of the hyth-ostanc load increases lineariv with water depth. Limit of Moderate Wave Action (LiMWA) — The boundary line given by FFAIA on coastal trial) Studies inarkint'r the extents of Coastal A Zones. I-) Lowest oor — The lowcst floor of the lowest enclosed area of a building, including as base- n1ell.L. Any NITIP-cornpliarit, unfinished or flood -resistant enclosure usable solely for parking of vehicles, bnilding access, or storage (in an area other than a basement) is not considered n a huilding's IMNITSL floor, provided the cnclostn-c does not render the structure in violation of the. applicable des],-n 1-C(jU11'CHJCHt5 of the 'NF1P. Mitigation Directorate —The component of'FENLN directly responsible for adininistefing the flood ha/,ard identification and floodplain irianagernent aspects of the NFIR Newconstruction—For floodplain management purposes, newconsrruciion means sul-LICLUres for which the start Of C0uStrL1C1iOri commences on or after the effective date of a floodplain managen-it.,ni, regulation adopted by a communiti, and includes subsequ.ent improvements to tile structure. Registered Desini Professional —An individual who iL,s registered or licensed to practice their n respective design lD1-0feSSi0u aLs defined by the stati-IlOry requirements, of the professional reg- istration laws of the State or.jurisdiction it) which the project is to be Constructed. Special Flood Hazard Area (SFHA) —An area delineated on to FIRM as being sub" ,jcc[. to mun- dation by the base flood. Standard residential garage door — A ([()Or, LNFplcallv up t€r 18 Beet Wide bNT up to 8 feet Lail, intended Use in a residential garage for vehicular access and normally expected to be op- erated less than 1,500 cycles per year, Technical Bul I eTin 9 — auGuST 2008 Substantial damage — Darna(l,-e ofany ori;in susiahied by a structure whereby the cost oC re- storing the structure to its bef-ore-damaged condition wOUld equal err- exceed 50 percent of the mm-ketVaIUC ofLhe strumtfe before the darnage occurred. Structures that.are determined I to be substancialh- daii-ialued pire corisidered to be substantial improvemerits, regardless of the actual repair work performed. Substantial improvement — Ariv reconsti-tictimi, rehabilitation, addition, or other improve- merit: of structure, the Cost of which equLds or exceeds 50 percetit of the market value ot'the Slr-LLCtttre (or smaller perccritzige ifestal-Aislicd by the commi-mity) before the -start of'cori- ,S]LrucLioll" of the improvement. This terra iriclude.s swLictIIITS Ll'tat have irICUITed "SUIDSLMILial clmiage," regardless of (lie auLtal repali- work performed. I Technical Bul I eTin 9 — auGuST 2008