b'An Evolving Concern with a TPO recover system or de-Asnoted,therehavebeenciding to forgo the tapered insu- PROBLEMS AND ISSUES WITH STRUCTURAL CONCRETE THAT RETAINS MOISTUREmanydiscussions,articles,advi- lation when the existing structure soriesandpresentationsaboutdoesnothaveextensivepond-thepotentialforaconcreteing).WhilethebetterselectionDetermining when a deck is ready for roofing Loss of R-valuedecktoretainmoisture,par- to eliminate ponding water may very well be to use tapered insu- Measuring concrete moisture content Microbial growth potentialticularlywheninstalledoveralation,giventhatthermoplastic non-ventingsubstrate.RetainedLoss of adhesionWater-based adhesive curing and re-wetting moisture, then, is something thatmembranes generally perform in needs to be addressed to ensureareas that pond water, the deci- Blistering Corrosion of roof fasteners and other ferrous-the installed roofing system willsion to forgo tapered insulationcontaining roof componentsperform, and a commonly useddoesnotnecessarilymeantheInsulation facer delaminationsolutionistorestrainmoistureentire roof wont perform. How-movementfromthedeckintoever, if a concrete deck does notTable 2theroofingsystemthroughthedry or retains moisture and the useofavapourretarder.Obvi- solution to address this condi- 3.What is the long-term vi- over a deck that containsnot be known. Prior to doing this, ously there have been other solu- tion does not work, the cost ofability of fasteners into aasignificantamountofwemusttakeintoaccountthat tions proposed, such as using ad- failure is generally high.concretedeckthatcon- moisture? not only is the vapour retarder re-mixtures in the concrete to lockWhat, then, is changing? Sim- tains much moisture? Will6.What has historically madestricting the movement of mois-inthewateroraddingrooftopply put, we suggest the standardthefastenersprematurelythe best vapour retarder? ture into the roofing system, in vents to remove the water; how- of care may not be enough, andcorrode due to the wet en- thecaseofasystem(insulation ever,thesesolutionshavebeenwe should remove our biases thatvironment? Rethinking Vapour Retarders included) that is adhered to the metwithskepticism,giventhehavebeenbornbasedonwhat4.How do you install a va- Ourroofingindustrydoesvapour retarder, it is also critical cost of failure should they nothas worked in the past. Considerpour retarder that will per- havesignificantexperiencethatto the attachment of the roofing perform their intended purpose. the following questions:The concept of the cost of fail- 1.How well will a vapour re- form if you have questionscan be drawn upon to arrive at so- system. Conversely, where attach-ure is critical to understanding thetarder adhere to a concreteyou cant answer about itslutions that not only address thement is through the vapour re-potential magnitude of this issue.deckthatcontainsasig- attachment to the deck? needforavapourretarder,buttarder, questions arise about how For some roofing problems or de- nificant amount of water?5.Regardingself-adheringshouldhelptheroofingsystemmuch moisture is going to be re-sign conundrums, the cost of fail- 2.Does cyclical vapour drive/ vapour retarders, what testperform when there are other fac- stricted when you fasten through ure can be relatively low (e.g., de- pressure portend a poten- method is indicative of per- tors to consider or where the an- the component that depends on ciding to use a tapered insulationtial attachment problem? formancewheninstalledswers to all of the questions maylowpermeabilityforitsperfor-ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 2 20209'