In the home that we’re building right now, we installed 9″ strips of 3/4″ Advantech we had lying around over our top plate and taped them to the ZIP sheathing at the eaves. This way we can strap the ceiling and then install poly that we can seal to the Advantech and create a continuous air barrier. On the gable ends, our contractors insisted they needed to overlap a run of sheathing between the gable trusses and the wall below for shear strength so we couldn’t tape the ZIP to the Advantech there. That seemed fine to me and we planned to just caulk the edge of the Advantech on those ends to maintain the air barrier.
They sheathed the gable trusses before they were installed, but failed to account for the 3/4″ of Advantech when they did that, so now that the trusses are installed, there’s a 3/4″ gap in the sheathing that spans between the gable trusses and the wall below (picture attached).
I’m worried that the air space behind the ZIP tape could eventually cause it to fail at the intersection between the gable sheathing and the wall sheathing. I was considering just taping the interior side of that gap. Does anyone have a better/more durable solution to this? Or am I worrying over nothing?
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I don’t think I’d worry about that seam more than any other in terms of air barrier or OSB failure. If you’re using spray foam insulation, it’ll fill that gap. If not, you could hit the gap with canned closed-cell spray foam as a backup air seal that’ll simultaneously fill the void.
If it's a big deal then just put a strip of OSB and hold with a construction adhesive. Simple enough.
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