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I am drywalling my unheated, partially-below grade exterior garage. A four-foot tall concrete wall runs along the parts of the garage that are below-grade.

Above the concrete walls are 2x6 wood framed walls. The wood is anchored to the concrete and separated with a sill gasket. There is a 1/2 inch ledge so the drywall will be flush with the concrete.

What can I do to transition between the drywall and the cement? I don't want a gap, and I suspect the drywall shouldn't be in direct contact with the concrete.

Before and after: Left: concrete and wood framing, right: concrete and drywall

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    What is the level of the exterior surface/grade? Is the 2 x 6 sill plate below grade? What is the current situation with the outside wall, how is the exterior surface treated? can you be reasonably confident that there will be no moisture penetration from the exterior, at the sill plate?
    – Jimmy Fix-it
    Commented Apr 26, 2016 at 1:45
  • What qualifies as a "gap"? Any seam at all?
    – isherwood
    Commented Apr 26, 2016 at 13:16
  • The concrete comes 18" above the grade. I just finished backfilling outside the walls after applying a waterproof membrane.
    – shufler
    Commented Apr 26, 2016 at 16:52
  • A seam is fine. This is a garage and I'd rather dust and stuff don't get in the crack between the drywall and concrete
    – shufler
    Commented Apr 26, 2016 at 16:53
  • Also, the outside wall on the other side of the wood framing is OSB with siding that ends below the sill plate
    – shufler
    Commented Apr 26, 2016 at 17:00

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In my last house a daylight basement the original sheetrock was glued to the cement walls with liquid nails that worked very well. I did pull it all out and add furring for electrical spaces. (I don't like exposed conduit and surface boxes in a room that became my man land). If you are worried about cracking at the sill add a accent trim over the gap.

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  • Accent trim -- so like moulding or something similar to a chair rail?
    – shufler
    Commented Apr 26, 2016 at 16:57
  • Yes it would look good and keep it sealed.
    – Ed Beal
    Commented Apr 26, 2016 at 17:17
  • I'm not sure how this answers the question, since the OP has framed the drywall 1/2" shy of the concrete so that the drywall finishes flush with concrete. So have you suggested to fur the framing out?
    – AdamO
    Commented Oct 5, 2023 at 18:34
  • I said framed the drywall, I meant the backing. Hope it makes sense.
    – AdamO
    Commented Oct 5, 2023 at 19:49
  • @adamo do u understand that it is normal to have a gap between the drywall and the concrete? Then a trim piece is added to hide the gap this prevents moisture from wicking up and the furring strips provide a nailer for the Sheetrock. This is how most pro’s do this unless it is a flip where as cheap as possible is the rule and it only needs to look nice for 90days the base boards or mopboards are the most common finish and as this was an accepted answer with multiple up votes ~ 7 years ago it must have been understood and answered the question that’s what the green check mark means.
    – Ed Beal
    Commented Oct 6, 2023 at 19:15
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One possible solution (there are no doubt others, and I'll be interested to see what they are) is to set a strip (4 to 12" wide) of 1/2" cement-based tile-backer board at the bottom edge of the drywall.

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  • That's an interesting idea. While I could mud the joint between the drywall and backer board, I think I would still have a gap between the backer board and concrete.
    – shufler
    Commented Apr 26, 2016 at 16:59
  • Caulk or mortar could fill that gap.
    – Ecnerwal
    Commented Apr 26, 2016 at 19:34
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In my experience concrete still gets wet even when above grade. That's why the sill plates even for above grade basement foundations will require moisture aversion, whether using treated lumber or a sill gasket.

I'm drawing up plans for finishing out a similar wall in my basement. I haven't done this yet, but my approach might be some z-channel flashing with a small 1/2" reveal to visually transition between two surfaces and to keep the drywall out of contact with the moist concrete.

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