Basement closet wall with foam needs drywall for fireproof?

Discussion in 'Remodel Forum & Blog' started by lmei007, Jun 4, 2016.

  1. lmei007

    lmei007 Member

    Joined:
    Sep 21, 2007
    Location:
    Maryland
    I have a closet in the basement. One of the walls has foam between the closet wall and the concrete wall. Do I have to put dry wall there for fire code?
     

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  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Yes, it needs to have a standard timed thermal barrier against ignition to meet code. Half inch gypsum board works.

    Before you close it all up:

    Are the seams in the foam panels air sealed with can-foam or caulk or something?

    How thick is the foam?

    How much of the foundation wall extends above grade?

    Code min performance for foundations in most of MD (US climate zone 4A, except Garrett County, which is zone 5A) is R10 continuous insulation. While technically that could be met with 2" of blue XPS from a labeled-R point of view, it's long term performance is closer to R8.5. For at least the top half of the wall (down to a couple feet below grade) it's probably worth adding batt insulation even if it's 2" foam. If it's thinner than 2" adding batts is advised too. Only unfaced batts or kraft faced, not foil faced, and DON'T install interior side vapor retarders other than standard latex paint on the half-inch wallboard.

    If there is any chance at all of a flood you may want to stop the batt insulation above the anticipated high-water mark.
     
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  4. lmei007

    lmei007 Member

    Joined:
    Sep 21, 2007
    Location:
    Maryland
    I cannot understand this part. I cannot imagine where are these seams located?

    2" and it is a full basement and almost entire basement walls are under the ground.
     
  5. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The boards are only 2' wide, so there are seams between adjacent panels. Those seams leak air unless sealed somehow, and sometimes that becomes a moisture problem. You can use 1 part expanding foam, or polyurethane caulk, or purpose made tapes. The top edge and bottom edge of the foam needs to be sealed too where it meets the slab and whatever is above. At the top of a foundation it's common to have a horizontal chunk of foam over the top of the foundation leading up to the foundation sill plate.

    [​IMG]

    At 2" it meets the letter of code for R-value but it's still worth adding batts to the top half of the wall. "Contractor roll" R13s are usually cheap enough to make that worthwhile.
     
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