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Community and Q&A

Practical way to air seal an interior soffit with Airtight Drywall?

DarkNova | Posted in General Questions on

I’m planning on using the Airtight Drywall Approach for my ceiling plane, but have a few interior soffits planned (for example a drop from the 9′ ceiling to the top of the kitchen cabinets). I’m assuming that with ADA, it would be best to not leave the top of the soffit area open but rather keep the air barrier at the same level (right below the roof trusses)?

So what is a good practical way of doing this? Would one install drywall on the top of the soffit (level with the main ceiling plane) and tape it with drywall tape, and then drywall the rest of the soffit? Or use something like OSB on the top of the soffit and use a good tape from the attic side to connect that to the adjacent ceiling drywall? Or a different method? Thanks.

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  1. Expert Member


    If you aren't putting in a lot of penetrations into the bulkheads that might leak, like pot-lights, then I don't see that it makes any difference where your air-barrier is, as long as it is continuous.

    There are two other reasons to seal the top of the bulkheads though. The first is to contain whatever insulation you are using above the ceiling. The second is that bulkheads act as "concealed spaces" which allow fire to spread between the wall and the roof, so most (all?) building codes require fire blocking.

  2. GBA Editor
    Martin Holladay | | #2

    Most builders would use Option A ("install drywall on the top of the soffit, level with the main ceiling plane, and tape it with drywall tape").

    But Option B ("use something like OSB on the top of the soffit and use a good tape from the attic side to connect that to the adjacent ceiling drywall") would also work.

  3. STEPHEN SHEEHY | | #3

    Probably quicker and easier to drywall the whole ceiling plane at once, rather than stop the drywall and fill in the space with OSB and then tape. Would the area above the soffit be extensive enough to use as a utility chase?

  4. DarkNova | | #4

    Yes, the soffit area would be deep enough to use as a utility chase in those areas. I still need to figure out where the soffits will be, to try to plan how utilities could be routed through it, but I think that would be a good idea.

    This brings up a related question -- I am planning on installing drywall gaskets along the top of the partition walls for the airtight drywall approach. If the drywall crew is not familiar with the "airtight drywall approach", is there anything special that they need to do, or do they pretty much just install drywall the way they always do (as long as I have the gaskets already installed)? I'm not that familiar with how drywall is installed -- do they do all the ceiling pieces first and then the walls, or do they go room-by-room?

  5. Expert Member

    They generally do all the ceilings first, so if that's when the gaskets can get disturbed, as they slide the board up the walls near the top. Gaskets don't alter how they board the house, but getting them onside about what you are trying to do will make them more careful.

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