b'Technical Article siteconditionsmayinfluenceloadconstantlymonitored.Attheendthe roof areas for all zones. It is also values in ways not captured by theof the test period, an investigationimportant that the designer under-tools calculations; for instance, lo- is carried out to understand the dy- standswhetherthemanufacturer cationsthatexperiencewindtun- namics of the rupture, if any, and toproposes to meet the requirements nel effects in the downtown core ofassess possible improvement optionsby using the extrapolation method major cities. It is important to noteto enhance the performance of theset forth in the Wind Design Stan-that, as is the case with any tool, it isassembly (Figures 7 and 8). dard Practice for Roofing Assemblies the users responsibility to verify the(ANSI/SPRI WD-1) 10that provides values generated by Wind-RCI. 7 Challenges Experienced incalculation means to enhance secure-Meeting the Wind Upliftment. If that is the manufacturers Third-Party LaboratoryRequirements intention, the manufacturer should Testing to Rate RoofAnissueexperiencedinthein- provide the details of calculation and Assemblies dustry is for the designers to transferany other information that the de-CSA A123.21 1is a rigorous testtheresponsibilityofdeterminingsigner may require to assess the risk. methodthatsimulatestheeffectswind uplift requirements to roofingThe designer should assess the suit-of wind pressure on a roof assem- contractors and/or manufacturers byability of the extrapolation method Figure 6: Airtight chamber mounted over the roof specimen. blyspecimen.Thetestmethodisreferencing the building code in theby verifying the calculation and tak-straightforward:acomplete3.7specifications, rather than specifyinging into account the mode of failure 7.3 m (1224 ft.) specimen com- therequiredproject-specificwindexperienced during the original test. posed of the layers of the tested roofuplift values. However, it is prudentWhiletheextrapolationmethod assembly, which may include a ther- for the designers to be informed ofmay be appropriate for mechanically attachedroofingsystems(MARS), mal barrier, a vapour retarder, insu- thecoderequirementsandeitherit is not suitable in all circumstances lation layers, cover board and a roof- verify the project-specific wind up- for fully adhered roofing systems or ing membrane system, is installed onlift values themselves or engage qual- partiallyadheredroofingsystems a deck, usually of corrugated steel,ified professionals to provide verified(PARS). For instance, if a roof as-attached to a specially designed testvalues. Doing so eliminates ambigu- semblys mode of failure is due to rig (Figure 5). An airtight chamberity, upholds the standard of care, re- cohesive failure of one of the layers is then placed on the specimen toduces risk and liability, and preventsofaroofassemblyatitsultimate ensureairtightnessatthejunctioncuttingcorners.InJune2018,thecapacity, improving the adhesion of where the chamber meets the benchCanadian Roofing Contractors As- the layers by reducing the spacing of (Figure6).Anairsuctionsystemsociation issued an advisory bulletin 8 the adhesives (which is a common Figure 7: Destructive testing upon completion of a test to evaluate the mode of failure. andcomputer-controlledshutterstocommunicatetheresponsibilityapproach for extrapolation) will not modulate the pressure and durationof confirming project-specific windimprove the overall performance of of the vacuum created in the cham- uplift loads lies with the designer andthe roof assembly. Regardless of the ber, simulating the pressure effectsnot the roofing contractor, and theamountandspacingoftheadhe-experiencedbyroofsduringtheirreasoning for this design responsibil- sive, the roof assembly will experi-service life.ity has been dissected at length byence cohesive failure of the layer at ThetestprocedureconsistsofKlassen in a 2021 article. 9 itsultimatecapacitybeforereach-consecutiveloadcycles,inprede- In addition to verifying the proj- ing the project-specific wind uplift terminedsequences,dividedintoect-specificwindupliftvalues,theresistance values. The designer may five levels and two methods, and itdesignermustobtaintestreportsspecificallynotethatextrapolation iscarriedouttoassessmaximumsupplied by a third-party testing fa- methods of compliance and the use stressuntilanevidentrooffailurecilitythatusesapparatusproperlyofnon-calibratedtestingfacilities isobserved.Thetestmaylastupcalibrated as per the CSA A123.21 1 areunacceptable.Thesafestap-to 10 hours, depending on the per- protocol, and verify that the testedproach is to ensure that the rating formanceoftheassembly,duringratingoftheproposedassemblyof the proposed roof system is con-whichtimethetestpressuresandmeets the project-specific wind up- firmedthroughthird-partytesting Figure 8: Mode of failure observed upon completion of testing. behaviour of the roof specimen areliftloadrequirementsforeachofand meets or exceeds project-specific LEADERS IN ROOFRoong solutions, whenVACUUM SALESand where you need them. Call For A Quote651-398-3029With our nationwide network,emiroofvacs.comcount on fast, reliable delivery anywhere in Canada.Get startedServing Southwestern Ontario Since 1972with QXO Commercial IndustrialServing contractors across OntarioMaintenance SpecialistsCambridge | Concord | London | Mississauga | Ottawa Free Estimates / InspectionPeterborough | Whitby and more 152 Thames Rd. W., Exeter, Ont. N0M 1S3 Tel: (519) 235-2802Fax: (519) 235-1532Email: speat@hay.net16ONTARIO ROOFING NEWSISSUE 3 2025 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'