Trapped moisture on SIP roof
I knew SIPs were the Achilles heel of my 100% engineered house design, But because of inattention to detail, heavy rains at a critical time of my house build pushed water underneath the PVC membrane (applied on mechanically fastened DensDeck) onto my SIP. It happened the night before the adjacent wall could be spray foamed to properly seal off the membrane. Unfortunately, the spraying was later done to the walls and the underside of the SIPs without knowing there was water present. It took a lot of effort on my part to get the roofer to even understand there was a problem and the fix they performed, in hindsight, turned out to be woefully inadequate. The true nature of the problem only became apparent when carpenter ants showed up 11 months later in the ceiling–indicating a really big problem (I regard them as heroes actually for alerting me to the issue). My own probing up through the SIP gaps revealed moisture content above 25% on the underside of the SIPs’ upper ply. At least it’s exterior ply instead of OSB, but roughly 1000sqft are affected. The roof is shed-style with a 2% slope. Clearly the membrane needs to be peeled and Densdeck removed. but how the heck can one now let a bare roof air dry while still protecting the SIPs (now sealed underneath) from the weather. Perhaps placing a new roof layer on top leaving ventilation over the original SIP surface? Has anyone had experience with this kind of repair?
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