b'Q5: WHAT IS THE WEAKEST LINK CONCEPT IN THE DETERMINATION OF WIND UPLIFT RESISTANCE?Wind induces load on the roof. It is resisted by each component by their resistance. This can be illustrated through a force resis tance link diagram respectively for MARS in Fig. 6, PARS in Fig. 7, and AARS in Fig. 8.All resistance links shall remain connected to ensure the system will be durable and keep the roof in place. Failure occurs when the wind uplift force is greater Q5: WHAT IS THE WEAKESTthan the resistance of any one or more of these LINK CONCEPT IN THElinks. This understand ing helps to choose the DETERMINATION OF WINDappropriate roof components and con struction techniques at the early design stage or byFigure 4. Typical component arrangement of a partially attached (hybrid) membrane roofing system.UPLIFT RESISTANCE? replacing/adding components to improve wind Wind induces load on the roof. It is resisted byuplift resistance during the reroofing. Q5: WHAT IS THE WEAKEST each component by their resistance. This cansure. This suction has two charac- TheCanadianmodelcodeLINK CONCEPT IN THE Q6: WHAT IS THE ROLE be illustrated through a force resis tance linkteristics: (a) it varies from one zoneNational Building Code of Can- DETERMINATION OF WIND OFSTRUCTURAL DECK?diagram respectively for MARS in Fig. 6, PARSDeck provides structural support, and it mustUPLIFT RESISTANCE?oftherooftotheother(spatialada (NBCC) specifies wind loadWind induces load on the roof. It is resisted by in Fig. 7, and AARS in Fig. 8.All resistance linkshave adequate strength and rigidity to supporteach component by their resistance. This can shall remain connected to ensure the system willvariations); (b) it varies from onerequirementstothedesignofbe illustrated through a force resis tance link dead and live loads. These loads either induce compressive or tensile forces or a combination be durable and keep the roof in place. Failureperiod of time to another (fluctua- roof assemblies for the nation. Indiagram respectively for MARS in Fig. 6, PARS occurs when the wind uplift force is greaterof forces. Steel, conc rete, and wood are threein Fig. 7, and AARS in Fig. 8.All resistance links tion with respect to time). One canthe U.S., the American Society ofshall remain connected to ensure the system will common deck materials used for the MARS/ than the resistance of any one or more of theseAARS/PARS. There is a lot of research related to the use of steel decks on commercial roofbe durable and keep the roof in place. Failure links. This understand ing helps to choose thesimplify the spatial variations fromCivil Engineers (ASCE) standardoccurs when the wind uplift force is greater appropriate roof components and con structionzones of higher to lower suction assystems. Therefore, this article only focusesthan the resistance of any one or more of these 7iswidelyused.Inaccordance on the use of steel decks on commercial roofs. techniques at the early design stage or byFigure 4. Typical component arrangement of a partially attached (hybrid) membrane roofing system. links. This understand ing helps to choose the corner, edge and field. A statisticalHowever, although SIGDERS has limited research replacing/adding components to improve windwith the ASCE 7 or NBCC or us- appropriate roof components and cons truction data on concrete deck and wood deck, bothal component arrangement of an adhesive applied membrane roofing systemuplift resistance during the reroofing. approachisusedtosimplifytheing Wind-Roof Calculator on theFigure 5. Typic techniques at the early design stage or byFigure 4. Typical component arrangement of a partially attached (hybrid) membrane roofing system.deck types are known for having moistureFigure 4. Typical component arrangement of a partially attachedFigure 5. Typical component arrangement of an adhesive applied replacing/adding components to improve wind timefluctuationsasmean,peakmigrationissues. (hybrid) membrane roofing system. uplift resistance during the reroofing. membrane roofing system.Internet (Wind-RCI) at nrc.can-Q6: WHAT IS THE ROLEThe wind uplift induces tensile forces, and standard deviation (Fig. 1). which are transmitted to the deck throughQ6: WHAT IS THE ROLE OFSTRUCTURAL DECK? dada.ca/en/researchdevelopment/Deck provides structural support, and it mustthe structural or pneumatic load path or aOFSTRUCTURAL DECK?products-services/softwareap-combination of both. Therefore, the decks Deck provides structural support, and it must have adequate strength and rigidity to supportQ2: What Are the Steps intensile strength and its attachment to the joistshave adequate strength and rigidity to support plications/wind-load-calculators-dead and live loads. These loads either induceare critical as they can influence the wind uplift re a tanceof a roof syste a dead and live loads. These loads either induce compressive or tensile forces or a combinationthe Wind Uplift Design ofroof-cl sis ddi ngveget m. ted-roof-as- compressive or tensile forces or a combination of forces. Steel, conc rete, and wood are threeof forces. Steel, con crete, and wood are three a Roof? sembly, calculate the design windcommon deck materials used for the MARS/ a) deck attachment methods common deck materials used for the MARS/withjoistsAARS/PARS. There is a lot of research relatedThecomplexprocesscanbeload (PD) for various zones of theAARS/PARS. There is a lot of research related Welding or fastening to a struct ural joist are theto the use of steel decks on commercial roof to the use of steel decks on commercial roofroof cladding (for example: field =systems. Therefore, this article only focuses simplified into three steps, and atwo common field attachment practices. Two systems. Therefore, this article only focusesidentical sets (welded versus fastened) of MARSson the use of steel decks on commercial roofs. on the use of steel decks on commercial roofs.case study is presented below. 1,341 Pa [28 psf], edge = 1,724 PaHowever, although SIGDERS has limited research with modified bitumen (MB) and thermoplas tic membrane were constructed and investigated at However, although SIGDERS has limited researchStep1:CalculatetheDesign[36 psf] and corner = 2,681 Pa [56data on concrete deck and wood deck, bothFigure 5. Typical component arrangement of an adhesive applied membrane roofing systemthe Dynamic Roofing Facility (DRF) of the NRC.deck types are known for having moisture data on concrete deck and wood deck, bothSpecimens that were is an online cal- emigrationissues.Wind Uplift psf]). Wind-RCI installed on decks that werFigure 5. Typical component arrangement of an adhesive applied membrane roofing systemdeck types are known for having moisturefastened to the joists performed better than theThe wind uplift induces tensile forces, migrationissues. welded specimens. The weld was the weakestFigure 6. Force resistance link diagram: mechanically attachwhich aeredtrroaonfsimngit steydste tom. the deck through The wind uplift induces tensile forces,link, as shown in Fig. 9. the structural or pneumatic load path or a The most common decks used in North Americaandc otemstbeidn aatti othne o Df bRoF tohf.tThhee NreRfoCr.e T,h teh efi drset cks which are transmitted to the deck throughb) deck strengths are 22 ga and 20 ga with 230 MPa (33 ksi) andspetceim nseilnetshtraetn wgatshiannsdta iltles da totanc 2h2m gean,t 5 t5o0 th Me Pjoai sts the structural or pneumatic load path or aSteel deck strengths are determined by the550 MPa (80 ksi). Two identical MARSs withsteealr ed ecrcikt ihcaald a asltohweye rc asuns itnafilnueedn cper ethsseu wrein odfuplift combination of both. Therefore, the deckscombination of the thickness and yield strength.thermoplastic membranes were constructed7.90reksPisat a(1n6ce5opfs af)rtohoafn s tyhsete smec.ond system, and tensile strength and its attachment to the joists are critical as they can influence the wind uplift12IIBEC Interfacea) deck attachment methods 2025January resistance of a roof system. withjoistsWelding or fastening to a struc tural joist are the a) deck attachment methodstwo common field attachment practices. Two identical sets (welded versus fastened) of MARSs withjoists with modified bitumen (MB) and thermoplas tic Welding or fastening to a struc tural joist are themembrane were constructed and investigated at two common field attachment practices. Twothe Dynamic Roofing Facility (DRF) of the NRC. identical sets (welded versus fastened) of MARSsSpecimens that were installed on decks that were fastened to the joists performed better than the with modified bitumen (MB) and thermoplas ticwelded specimens. The weld was the weakestFigure 6. Force resistance link diagram: mechanically attached roofing system.membrane were constructed and investigated atlink, as shown in Fig. 9.the Dynamic Roofing Facility (DRF) of the NRC.The most common decks used in North Americaand tested at the DRF of the NRC. The first Specimens that were installed on decks that wereb) deck strengths are 22 ga and 20 ga with 230 MPa (33 ksi) andspeci men that was installed on 22 ga, 550 MPa fastened to the joists performed better than theSteel deck strengths are determined by the550 MPa (80 ksi). Two identical MARSs withsteel deck had a lower sustained pressure of welded specimens. The weld was the weakestFigure 6. Force resistance link diagram: mechanically attached roofing system. combination of the thickness and yield strength.thermoplastic membranes were constructed7.90kPa (165 psf) than the second system, and link, as shown in Fig. 9. Figure 6. Force resistance link diagram: mechanically attached roofing system. 12IIBEC InterfaceJanuary 2025The most common decks used in North Americaand tested at the DRF of the NRC. The firstthe failure mode was determined to be due to b) deck strengths are 22 ga and 20 ga with 230 MPa (33 ksi) andspecimen that was installed on 22 ga, 550 MPathe fmaielumreb rmanoed efa wst aesn deer thearvmininge pdu tlole bde o duut efr toom Steel deck strengths are determined by the550 MPa (80 ksi). Two identical MARSs withsteel deck had a lower sustained pressure oftheec km, aesm sbhroawnen fians Ft eign.e 1r 0h.a Tvhineg s epcuollneddsopuetc firmomencombination of the thickness and yield strength.thermoplastic membranes were constructed7.90kPa (165 psf) than the second system, anddwdeacsk i,n asst aslhleodw onn i n2 0Figga. ,1 505. 0T hMe Psae csotenedl sdpeeccki men anads ipnasstsaellde da osuns 2ta0ingead,5p5re0s MsuPrea sotfe 8e.l6 d2e kckP a w12IIBEC InterfaceJanuary 2025 a1n8d0 ppassfs)e.d a sustained pressure of 8.62 kPa ((180psf).Q7: WHAT IS THE ROLE O7FM: WEHMABT IRAS TNEH?E ROLE QCoFMOmmoEn mMeBmRbrAanNesE a?re ther moset, t obsetra, ne must Choemrmmoopnl amsteicm, abnradn MesB a. rTeh teh merem mhhaevrem aodpelqaustaitce, asntrde nMgBth.Ttoh ew mithesmtabnrdan teh em sutrsets s thraovme awdinedq uuaptleif st.t rTehneg pthh ytosi cwailt/hmsteacnhda nthicea sl tress ffrroompe wrtinieds uopf ali fmt. eTmheb prahnyes iscualc/hm aesc thhainckicnael ss and pternospieler tsietrse onfg ath m veamryb froanmepsruocdhu acst thoi pckrondeussc ta nd pdeenpseilned sitnrgen ognt hth vea cryh efrmomica pl rcoodmupcto tsoit piorno dauncdtthe tdeeinpfeonrdceinmge onnt mthaet cehrieamls.i cAasl csohmowpno sinit iFoing .a n11d ,t thheermreienmfobrrcaenmee wnat sm satrtertciahles.d A asr oshuonwd nth ien fFaisgt.e 1n1e,rthe mlaetmesb,r laenaed iwnags i ts troe ptcuhlel odu atr foruonmd t thheeffaasstteenneerrpplate;s ,t hleisa disi nkgn oitw ton pasu ltlh oeu tc foromkie t hcue tfa fsatielunreer.In Figure 7. Force resistance link diagram: partially attached (hybrid)phlaist ec;a tshei,s t ihse k mnoewmn b aras nthee w acso othkeie w ceuatk efasitl ulinrek. fIonrFigure 7. Force resistance link diagram: partially attached (hybrid) membrane roofing system. tthat roofing system. Replacing it with a thicker membrane roofing system. this case, the membrane was the weakest link for Figure 7. Force resistance link diagram: partially attached (hybrid) membrane roofing system. ahnadt/ rooro hfignhge sry tsetnesmil.e R setrpelnacginthg m it ewmitbhr a nthei cwkiellrthnedlp/ otorhinigchreear ste nthseil ew sitnrde nugptlhif tm resmisbtarannce wofi ll athheelps ytos tienmcr.ease the wind uplift resistance of theMseymstebmra.ne seam strength is an importa nt parMamemetberra tnhea ts einafmlu esntrceensg wthin idsaunp ilmiftp roesrtisa tatn ce nina MramAReSte. rT hthea ste ianmflu menucset sr ewsiinsdt f uluptltieftrirnegsi astnadn ce pinu MllinAgR Sfo. rTcheessdeuaem to m wuisntd r euspislitf tf lfuotrtceer.inSgo manedpmualnlinugfa fcoturcreesr sd suuep tpol yw minedm ubplriafnt feosr cwei.t hS ofamcteo ry pseanmusf,a bcutut rmeros sstu opfp thlye m meamnburfanc teusr ewrist hre fqacutiorer y mseamisn, gb udtu mrinogst c oofn tshteru mctaionnu.f aTch teurree arsr ere thqrueireedeifafmerienngt dtyupreinsg o cf osenasmtru acptipolnic. aTt hioenre m aereth thodresesdoirf fMerAenRtS t. yTpheesr mofo spelaamst iac pmpelimcabtiroann em seetahmods sa re ffoort M-aiAr RwSe.l Tdheedr bmyo ap rlaosbtoict imc memac bhriannee. Tsheeamrmso asrethhoetm-aibr rwaenled seeda bmys a h raovbeo ttaicp me anchdi/noer .a Tdhheersmivoes.e t mMeBm mbermanb er asneeam sesa hmavs ea rtea phee atn adi/ro wr eadldheeds.i vTeh.emMIGBD mEeRmSbrersaenaer cshe asmhosw aeredhtheat uaisri nwge lidmepdr.o TpheerSspIGeDedE RaSn dre tseemarpcehr ashtuorwe efodr t hoat /uhseinatg a iimr wperoldpienrgSspseueldts a in datveemryp wereaatku rsee afomr ,h aost /shheoawt na iirn w Feilgd.in1g2 .reresaunlutsfa icnt ua rveerrsy h waveea kin sveeanmte, da sn sehwo wsena min Fig.12.MMpapnliucfaatciotunr teercsh hnaovleo ginieves nstuecdhnaes wse slef-aamdh ered aaepapmlic oarti toonr cthe-cfhreneo lsoegaimesisnu rcehc eans ts yeelfa-arsd,h weirtehdscleaaim so trh taotr cthe-f rneeew s eseamam in a prepcleicnatt iyoena rtse,c whnitohl -solgaiemss a trhea bt ethttee rn tehwa ns ethame t arapdpilticoantaiol nm tetchhondosl.-.cFigure 8. Force resistance link diagram: adhesive applied membrane roofing system. Fugriethse arr ree bseattrecrh t ihsa nne tehdee tdra tdoi itniovneaslt imgaetteh othdes oFigure 8. Force resistance link diagram: adhesive applied membrane roofing system. FFigure 8. Force resistance link diagram: adhesive applied membrane roofing system. wuerltdhinerg r wesineadrocwh i(ste nmeepdeeradt utore i navneds tsipgeaeted )t,h e theel dininflguewninced owf a (mtebmiepnetr taetumrpe earnadtu srpee teod ), wshteelf -iandflhuee rnecde s oefa amm abniedn tto trecmh-pfreerea tsueraem tos on wind ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO sepllfi-fatd rheseirsetdan sceea.m and torch-free seams on windONTARIO ROOFING NEWSISSUE 1 202515uupFlioftrrtehseis MtaAnRceS. with thermoplastic membrane, theFroer a trhee t MwoA RseSa wmitinhg th tecrmhnoipqluaessti,c o mnee-msidbera wnel,d (OtheSrWe )a raen dtw doo suebalme-isnidge t ewcehlndi q(DuSeWs, )o, naes -sshidoew wn eld iO SFWig).a1n3d. T dhoeu SbIlGeD-sEidReSwreesldea (rDcShW sh),o awse sdh othwen (nio oFfiign.g 1 s3y.s Ttehme S wIGitDh EDRSSW re pserafrocrhm sehdo wbedtt ethr eth rn an roSoWfin. gD SsyWs tseymst ewmith s uDsStWain peedr fao mrmineidm buemtt eorft1h5a%n OOiSgWhe. rD wSiWnd s uysptleifmt r esusissttaainceed t ah amni nOimSWum sy ostfe 1m5%.hhhigeh OeSr Wwi nsyds utepmlif td reevseislotapns caen t hasaynm OmSWet rsicyaslt efomrc. e TFigure 9. Deck weld failure mode. bhye p OulSliWng s tyhsete bmo tdtoemve lmopesm abnr ansyem. Tmhee tfraiscatel nfoercseTFigure 9. Deck weld failure mode. by pulling the bottom membrane. The fasteners January 2025IIBEC Interface13January 2025IIBEC Interface13'