Exterior closed-cell spray foam and “sheathing membrane” requirement
Hello all, my name is David and I’m well into a big renovation of my very little house in the inner-city of Calgary, Alberta.
Hopefully I will be able to share the whole story soon, but for now I turn to you for advice on satisfying a permit requirement for my exterior walls.
My wall assembly begins simply with original 2×4 framing, new r14 Rockwool cavity batts and original shiplap sheathing. Then I have built stand-off furring and had about 3″ of closed cell spray foam applied. A simple sketch is attached. I’ve also attached a couple photos. (fyi, the now cathedral roof consists of 5.5″ cc spray foam in the rafter cavities and 5″ EPS on top plus new eave extensions)
My original building permit did not include the walls so I have just received another one to cover everything just in case. However, there is a requirements that I don’t fully understand:
-Division B, 188.8.131.52 – Required Sheathing Membrane and Installation
I do not intend to add another layer of sheathing and to wrap the house seems a bit pointless to me. It was my understanding that the ccSPF in this application would serve as sufficient control layer for water, air, and vapour.
As you can see from the photo, I do have exposed wood on the furring that I will be attaching the siding to (likely KWP or Hardie). I wasn’t particularly concerned about that in our climate and I don’t think that’s what the membrane requirement is addressing anyway.
In the interest of keeping this brief, I’ll leave the explanation there and ask how you would finish this. Is there something I’m missing? Would simply treating/covering the exposed wood stand-offs be best?
Thanks in advance for your thoughts.
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