Unvented flat roof with SPF underside
Hi everyone, I live in climate zone 6. I had done allot of research (clearly not enough) when I decided to spray the underside of my flat roof with 5 inch of closed cell SPF. My understanding was this would create an air and vapour barrier and something like R28. However after the job, I noticed that it was in NO WAY a vapour barrier. They sprayed inside the joists only. There were places I could actually see the roofing membrane. I filled the small gaps in the SPF with great stuff. However there are many placed where the framing wood create small air leaks. Joists that are sistered for instance. or where the joists meet the wall framing. Any place where one piece of wood is nailed to another creates a place where air can leak up and touch the membrane. After watching this video: https://www.youtube.com/watch?v=Ld8pzIu45F8 i’ve been using silicon caulk to try to close up all the air leaks, but the likelyhood that i’ll be completely successful is slim at best. It’s an old building. I will also try to create a complete air barrier with the gyprock but again being perfect is hard and hard to determine. It only takes a small leak to allow allot of moisture though. I believe I’ve created a recipe for mould and rot, any advice on how to fix this now, short of ripping up the roof and putting a proper slanted roof on.
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