b'Technical Articleof CAN/CSA A123.21, which is the only compliance standard by the NBCC. The US has several wind uplift test methods, including FM 4474 and UL 1896.Three Decades of Scientific Step 3: CorrelationSelect a roofing system and related components with uplift resistance higher than Advancement to the North the design load (Fig. 2).Q3: WHAT IS CSA A123.21 AND Ame W WAS IT DEVR PED? fing CommunityHO ic n ELO or a oThe Canadian model code NBCC specifies wind load requirements for the design of roof assemblies. To comply with the NBCC, the CSA A123.21 standard provides testBy Appupillai (Bas) Baskaran, requirements for resistance evaluation.F-IIBEC, PEng, PhDTested resistance should be equal to or of CAN/CSA A123.21, which is the onlygreater than the design load. First publishedThefollowingarticleoriginallyap- Diagnosis of a weak link to en-in 2004, CSA A123.21 was subsequently compliance standard by the NBCC. The US hasrevised/ edited in 2010 and 2014, withpeared in the January 2025 issue ofable innovationseveral wind uplift test methods, including FMIIBEC Interface. It is reprinted hereNominal versus design tensile4474 and UL 1896. the latest edition published in 2020. Thewith permission. strength of steel deck, and the R&D for the standard was developed by theThispaperwaspresentedattheimportance of eachNational Research Council Canada (NRC)2024 IIBEC International Conven- Investigation of the innovation Step 3: Correlation industry-based Consortium, Special Interesttion and Trade Show. of membrane seamingSelect a roofing system and relatedFigure 1. Wind and its effects on a school building roof measured intawa. es between air leakage DifferencOtcomponents with uplift resistance higher thanGroup for Dynamic Evaluation of RoofingO n November 16, 1994, mem- and intrusionSystems (SIGDERS). bersoftheroofingcom- How much roof edge matters the design load (Fig. 2). munity met at the NationalWind science of vegetated roofsResearchCouncilCanada(NRC)Climateadaptationofcom- Q3: WHAT IS CSA A123.21 ANDQ4: WHAT ARE THEP = 2.87 kPa (60 psf) P D= 2.68 kPa (56 psf)of CAN/CSA A123.21, which is the onlyand formed a group with a commonmercial roofsHOW WAS IT DEVELOPED? DIFFERENT TYPES OFfocus of evaluating roofing systemsThese advancements were deliv-compliance standard by the NBCC. The US has several wind uplift test methods, including FMLOW-SLOPE MEMBRANEunder dynamic environment. Thus,eredwithdetailsconsecutivelyfor The Canadian model code NBCC specifiesaSpecialInterestGrouponDy- 20 years at the IIBEC conventions. 4474 and UL 1896. ROOFING SYSTEMS?wind load requirements for the design ofnamicEvaluationofRoofingSys- This article is an extraction from Step 3: Correlation The roofing assembly consists of a deck roof assemblies. To comply with the NBCC,tems (SIGDERS) was created. Theall those presentations. It will be de-Select a roofing system and relatedand roofing membrane. It may includemandate of SIGDERS joint researchlivered as a symbolic icon of the SIG-the CSA A123.21 standard provides test components with uplift resistance higher than the design load (Fig. 2). components such as vapor barrier or retarders,competitive ofbenefittoDERSs contribution to the North requirements for resistance evaluation. program is to carry out generic, pre- American roofing community. The Q3: WHAT IS CSA A123.21 ANDinsulation, cover board, etc. The roofingresearch Tested resistance should be equal to orall its members. SIGDERSs opera- article also highlights current R&D HOW WAS IT DEVELOPED? system con sists of components above theefforts at the NRC focusing on resi-greater than the design load. First publishedtion is one of a kind, not only for its The Canadian model code NBCC specifies wind load requirements for the design ofdeck. The standard is applicable to low-slopelegacy as a long-lasting research anddential and climate adaptation areas.in 2004, CSA A123.21 was subsequently roof assemblies. To comply with the NBCC,membrane roofing systems that fall in one ofdevelopment(R&D)consortium, revised/ edited in 2010 and 2014, with the CSA A123.21 standard provides testQ1: What Are the Attributes requirements for resistance evalu ation.three categories, each of which describes thebut also for the following industry the latest edition published in 2020. TheCAN/CSA A123.21Design wind data fromof Wind on Roof?Tested resistance should be equal to orway the roof system is secured to the deck/impacts it created: Building CodeR&D for the standard was developed by theor FM 4474 Staticversusdynamicevalua- Wind is a random process. When greater than the design load. First published in 2004, CSA A123.21 was subsequentlystructure as indicated below. tions of roofs, and the pros andit separates from roof edges, it cre-National Research Council Canada (NRC) revised/ edited in 2010 and 2014, withFigure 2. Wind uplift resistances should be higher than the design values.industry-based Consortium, Special InterestMechanically Attached Roofing Systemcons of each ates zones of suction (negative) pres-the latest edition published in 2020. TheFigure 1. Wind and its effects on a school building roof measured in Ottawa.R&D for the standard was developed by theFigure 1. Wind and its efsystem inschoothe roofing Group for Dynamic Evaluation of Roofing(MARS): a fects on awhich l building roof measured in Ottawa.National Research Council Canada (NRC)membrane is intermitt ently attached to the Systems (SIGDERS).industry-based Consortium, Special Interest Group for Dynamic Evaluation of Roofingdeck using fasteners, as shown in Fig. 3.Figure 1. Wind and its effects on a school building roof measured in Ottawa.Systems (SIGDERS). Partially Attached (hybrid) mem- P D= 2.68 kPa (56 psf)Q4: WHAT ARE THEP = 2.87 kPa (60 psf)DIFFERENT TYPES OFbrane Roofing System (PARS): a system in Q4: WHAT ARE THEP = 2.87 kPa (60 psf) P D= 2.68 kPa (56 psf)DIFFERENT TYPES OFwhich the roof membrane is bonded to the LOW-SLOPE MEMBRANE LOW-SLOPE MEMBRANE ROOFING SYSTEMS? substrate using adhesives, and a minimum ROOFING SYSTEMS?The roofing assembly consists ofof one component below the membrane The roofing assembly consists of a deck a deck and roofing membrane. It may include and roofing membrane. It may includeis intermittently attached to sup porting components such as vapor barrier or retarders,insulation, cover board, etc. The roofingcomponents such as vapor barrier or retarders,structure using fasteners, as shown in Fig. 4.system cons ists of components above the insulation, cover board, etc. The roofingAdhesive Applied membrane Roofing deck. The standard is applicable to low-slope system cons ists of components above theSystem (AARS): a system in which the roof membrane roofing systems that fall in one of three categories, each of which describes theCAN/CSA A123.21Design wind data fromway the roof system is secured to the deck/or FM 4474deck. The standard is applicable to low-slopemembrane is bonded to the substrate using Building Codestructure as indicated below.membrane roofing systems that fall in one ofadhesives, and all the other components Mechanically Attached Roofing SystemFigure 2. Wind uplift resistances should be higher than the design values.three categories, each of which describes thebelow the roofing membrane are integratedDesign wind data from(MARS): a system in which the roofingCAN/CSA A123.21 using adhesives, as shown in Fig. 5. igure 3. Typical component arrangement of a mechanically attached roofing system. membrane is intermittently attached to the way the roof system is secured to the deck/Figure 2. Wind uplift resistances should be higher than the design values. FFigure 3. Typical component arrangement of a mechanically attached roofing system.deck using fasteners, as shown in Fig. 3. or FM 4474 Building Codestructure as indicated below.Partially Attached (hybrid) mem-Mechanically brttached Roofing SysteminFigure 2. Wind uplift resistances should be higher than the design values. THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORNAane Roofing System (PARS): a system 14ONTARIO ROOFING NEWSISSUE 1 2025which the roof membrane is bonded to theJanuary 2025IIBEC Interface11(MARS): a system in which the roofing substrate using adhesives, and a minimum of one component below the membrane tmembrane is intermit ently attached to the is intermittently attached to sup porting deck using fasteners, as shown in Fig. 3.structure using fasteners, as shown in Fig. 4.Partially AttachAdh (hybrplied membrane Roofing edesive Apid) mem-System (AARS): a system in which the roof brane Roofing System (PARS): a system in membrane is bonded to the sub strate using which the roof membrane is ll tonded tmpone ts adhesives, and abhe other coo thenbelow the roofing membrane are integrated substrate using adhesives, and a minimumFigure 3. Typical component arrangement of a mechanically attached roofing system. using adhesives, as shown in Fig. 5.of one component below the membrane is intermittently attached to supportingIIBEC Interface11January 2025 structure using fasteners, as shown in Fig. 4.Adhesive Applied membrane Roofing System (AARS): a system in which the roof membrane is bonded to the sub strate using adhesives, and all the other components below the roofing membrane are integrated using adhesives, as shown in Fig. 5. Figure 3. Typical component arrangement of a mechanically attached roofing system. January 2025IIBEC Interface11'