Wall to ceiling air-sealing detail
I have seen designs where taped wall sheathing is carried inside to the ceiling for air-barrier continuity. This detail often includes a plywood or OSB flange, projecting inward at the top of the wall, before roof trusses are installed. The sheathing is taped up over the top of this flange, which is in turn sealed to the ceiling (tape, flashing membrane, etc.)
While this method provides a good air seal, it unfortunately interrupts the wall sheathing at the top plate. If you have a raised heel truss sitting directly above the wall framing, there is a significant structural advantage in spanning the wall, top plate(s), and truss heel with a single piece of sheathing. Many sources strongly recommend this practice, especially for windy locations, to strengthen the truss connection.
To air seal this assembly, could you caulk the above-mentioned flange piece to the top plate and then also caulk the sheathing to the outside face of the top plate? On the inside, the flange could still be taped to the ceiling. Will this method provide a reliable long-term air-seal?
I have attached a rough sketch (not to scale) to illustrate what I am suggesting. Thanks, Don
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