Rigid foam over zip osb
My wall assembly will consist of vertical vinyl siding, 2” of rigid foam, 7/16” zip osb, 2×6 wall with faced fiberglass, and gypsum board.
I’ve been planning to line the 2×6 wall plane with my 8” concrete foundation wall. That would result in about 2-1/2” of material protruding past the foundation. I’m not a fan of this but feel like this makes most sense since my zip osb will be the water and air control layer. This would also require me to protect the exposed rigid foam from below.
Another option would be to make the foundation 2” wider in all directions and use flashing to get any water off the mud sill.
Any thoughts of either of these options? A couple other things I am thinking about are whether I need a better drainage plane between the zip and rigid foam. I will probably tape the rigid foam, but prefer not to make that a water control layer unless someone can point out something that I am overlooking.
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