Sprayfoam house and real stone cladding. Wall sheathing?
This is my first post, but I want to comment how much I’ve enjoyed reading topics on this q&a forum.
My question is regarding a new house I’m building. Zone 8 climate (cold!) similar to Alaska, 2×6 framing 16″ OC walls, 1/2″ OSB sheathing, no basement. Right now I’m just finishing up framing.
I’ve been dead set on using closed cell spray foam all around…on the interior wall cavity at 3″ thick, 4″ on the roof deck and 1.5″ on the floor.
I’ve always been concerned about moisture and stories of wood rot from using spray foam. At the same time, I like that its a vapor barrier and I know that its well bonded to the studs/sheathing.
My question specifically is regarding application of real stone (travertine, 1-1/2″ thick tight stack cladding) on the outside of the entire building. I was hoping to use a product similar to Wedi board to cover the entire perimeter of OSB sheathing and then affix the stone directly to the Wedi with a exterior rated medium bed mortar. The Wedi board seams are sealed with polyurethane sealant to make it waterproof.
For those not familiar with Wedi, it is a 1/2″ thick XPS board with cement coating and fibremesh on both sides. I know its not vapor proof, but I’m unsure of its perm rating. I’d imagine around PERM 1 or so.
I’m worried now that the OSB will become sandwiched between the Spray Foam on the inside and the Wedi strofoam on the outside causing the OSB in the middle to rot over time.
I was set on using the Wedi XPS on the outside so that I could provide a thermal break to the studs, but I’m starting to think it may not be the best choice.
I’ve been told that perhaps a air gap, perhaps 1×4 strapping or similar before applying the Wedi to the outside might make it a better solution so the OSB can better dry should it get wet?
Sorry for the long post. I look forward to any replies.
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