Flange connection between wall and ceiling air barrier without strapping on the ceiling
Hello, I am planning to use the commonly mentioned method which places a flange on top of my exterior walls to connect the exterior sheathing to the interior drywall at the ceiling. Was originally planning to do the typical 3/4 plywood/osb flange, strap the ceiling, and put a bead of sealant under the flange. Thinking about it further, I would feel more confident about tape being used because I could see it and know it got done correctly by the subcontractor. I then considered can I just have the drywall installed against the 24oc trusses as is typical in my area and have them butt against the flange, then just tape the drywall to the flange from below? Thinking to use the 3m 8067 tape, if there is a better choice here please let me know. The other thing I have heard mention of being an issue is truss uplift causing drywall cracks, should I be concerned about that? Lastly, is there any concern about drywall properly holding up the weight of R60 blown fiberglass? I heard Steve Baczek mention once that 12oc strapping helps support the weight of the insulation in the attic… Making me think a 5/8in flange and drywall should be used instead of 1/2in.
So to recap:
1) Is there any issue with forgoing the strapping, creating a butt joint between the flange and drywall, then taping between them with something like 3m 8067? Was planning on using cdx plywood for the flange.
2) Should I be concerned about truss uplift destroying my air barrier over time?
3) Is 1/2in drywall here sufficient to stay intact against 24oc trusses and hold up R60 of blown fiberglass or should I go 5/8in?
Thanks!
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Replies
what is the benefit of a plywood flange over just draping membrane?
also if you are worried about truss movement and drywall, trim tex makes a corner bead designed to allow movement for this exact scenario.
You are right that a membrane would work here too. To be honest, I just have more trust in the plywood flange with taping getting executed properly compared to the membrane. But maybe I shouldn't worry about that. Doing any of this stuff isn't common for subs around here.
BuildingAHome,
One consequence of using a solid flange but no strapping is that your walls will be 3/4" higher. If (as is commonly done) you have used pre-cut studs, two sheets of drywall won't make it to the floor.
We will have a false ceiling being used in a few places to avoid having ceiling penetrations puncture the air barrier, so I think that will actually allow for 2 sheets as coming up short on the top would be okay. (Assuming my drywaller is using sheets wider than 4', which I am not sure of at this time, since our ceilings are taller than 8').