Wall penetration details with exterior rigid foam
TimandChristie
| Posted in General Questions on
How should I go about flashing wall penetrations after installing XPS exterior foam? Is it possible to flash to the exterior foam itself, or do I need to cut it back to the WRB (which in this case is our housewrap)? I’m starting to think it would have been ideal to flash penetrations before putting up exterior foam, but here we are.
Would it be possible to use a flexible flashing tape to flash the entire penetration from inside to outside or is that asking for trouble?
Building details: studs 24OC, 3/8 sheathing taped (air barrier), house wrap, 2″ XPS, 5/8″ Furring strips.
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Replies
Hi Timothy.
If the sheathing is your air barrier, that's where the penetration should have been air sealed and if the housewrap is your water-resistive barrier, that's where all of the flashing should be done.
I do feel like houses with both a WRB and exterior rigid foam are redundant and assume that the foam actually keeps most of the water that gets behind the siding from getting further into the wall. If the foam hadn't been up already, I'd have suggested flashing the penetrations to both the WRB and the foam. That's what I did on my house because it's cheap insurance.
However, if I was in your shoes, I think I'd be comfortable sealing the penetrations at the foam. Maybe use some canned spray foam deeper into the penetration for air sealing and flashing tape for water management.
I'll be curious to see what others think.