b'Roof Blisters Photo 5: This series of blisters occurred on a newly installed black EPDM roof membrane between a water-based adhesive and the membrane. The membrane surface temperature was in excess of 140 F and created plate blisters because the wet lay of the membrane and a water-based adhesive. The blisters will subside once the vapor is out of the system by solar heating.leftwithpressureequalstempera- The blister will continue this cyclenounced effect because a rise in tem-ture.ThisgoesbacktoWardensof growth, drawing in more air andperature makes water-laden air twice early work. If temperature goes up,water vapor nightly, as available, untilas pressurized as dry air. Kilo per kilo pressure must go up. When the tem- an equilibrium has beenachieved. (or pound for pound), water is twice perature goes down, pressure mustAlthough the Ideal Gas Law dic- as bad for pressurizing blisters.go down. This is the most basic de- tates the inner workings of a blister,Thereisanothermajorreason Think Safe, scription of a blister. If we add vol- those of us who have been around forwater can lead to blisters, which has Work Safe, ume, as pressure goes up and down,a while know wet substrates and wa- to deal with the creation of a void since 1988 the volume of the blister will growter make blisters worse. The pressurein a roof system. Remember, there and shrink accordingly with mem- of several gases, such as nitrogen, oxy- needs to be a confined volume of gas branes elasticity. gen, water vapor and benzene (ben- to create a blister. Water can create Top-Line Roofing & Sheet-Metal Inc. specializes in the installation, repair, and maintenance ofIfthepressureinsideablisterzene is used as a solvent in roofing ad- this void when a worker applies hot industrial roofs throughout Southern Ontario.growsandplacessufficientstresshesives and cleaners) can be stronglybitumen over a substrate with elevat-OUR SERVICES: onitsperimeter,therewillbeanaffectedbytemperature.Butwatered water content. Water will rapidly Commercial roofing Re-roofing adhesion failure at the perimeter ofvapor is by far the most influential. vaporize with heat, create voids and Roof maintenance Skylight installation theconfinedspaceandtheblisterOne way to understand the signif- prevent the typical bonding process, Roof inspection,Sheet metal flashing, evaluation & report fabrication & installation willgrow. icance of water vapor is to consider aleavinganareaofunbondedbitu-Historical restoration Retro-fit curb installation Think of this like a ratcheting ef- unit mass, such as a kilogram of eachmen that can become pressurized as Emergency roof repairs fect. As the daily heating cycle is ap- gas. Water vapor is twice as potent inmoisture migrates.plied, pressure can expand a blistera blister as air (nitrogen and oxygen)This reaction is similar to what is (905) 602-0760 to equilibrium to balance the pres- andfourtimesmorepotentthanoccurring in Photo 5. A void should 1325 Fewster Dr sure exerted inside the blister and thebenzene.Thisisonemajorreasonandtypicallydoescollapse,anda Mississauga, ONL4W 1A2toplineroofing.ca confiningforcesofthemembranewhywaterinaroofsystemmakesbond is made as the excess moisture anditsadhesiontothesubstrate.blisters worse. Water vapor has a pro- moves out and the water-based ad-16ONTARIO ROOFING NEWSISSUE 3 2024 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'