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The split-level we bought recently has a "basement" that is only partially underground. During heavy rain we had a leak that gave us an excuse to tear out the 70s-era faux wood paneling and replace with drywall. The concrete has been sealed and now it's time to install new materials.

The original setup was 2x2in wood columns with a 1x6in rail across the top. The vertical pieces were epoxied to the concrete. Most of that epoxy had long since failed and the 2x2s could be easily removed by hand. There was nothing attaching any of the wood to the concrete slab floor of the basement.

What is the best practice for supporting drywall? How should we affix a frame to the concrete wall and floor? Photos are from the demo period before concrete sealing showing the original shoddy 2x2 framing.

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This depends on whether you just want to put up drywall, or insulate as well. You're never going to have a better chance to do the latter.

Per This Old House, if you just want drywall or paneling, the best approach for a full-height wall may be to affix horizontal 1x2's to the wall using some mixture of concrete fasteners and modern construction adhesive, then screw 1x2's vertically to those on standard 16" to 24" centers to act as the "studs" which the wallboard is fastened to. The advantage of having two 1" (nominal) layers is that it gives you clear paths to run wiring either now or later. This is nonstructural so you don't need a header or footer, though fire codes may want you to seal the gaps at top and bottom with foam or leftover construction adhesive.

If you want to insulate, you have several options. One is to use deeper wall construction which has space to contain insulation; details depend on the kind of insulation you want to use. As an alternative, there are insulation products which have plastic studs built into them so you can just glue them to the wall, screw the wallboard directly to them, seal top and bottom (again), and be done. This works nicely on concrete foundation walls, less so on other construction; see the manufacturers' websites for details. These have wiring channels designed into them so you don't need to plan for that. Cost was roughly comparable when I did my own basement. (I used InSoFast and was generally happy with the product and customer support; I have no affiliation with the company and there may be others just as good or better.)

Note that in your case, since there is a "real" (hopefully insulated) wall above that step, you may not need all of this complexity. If your wiring can run through the framed upper walk, the bottom section can ignore that issue and just be cosmetic and, if desired, insulating. Putting a board on top to cap it and join it to the framed wall is perfectly reasonable, though you may need to scribe and trim that to match the walls shape unless you can slide it under the upper wallboard. (Nothing in a house is ever perfectly plumb, square, or straight.)

One possibly useful trick: I stopped the wallboard two inches above the floor, and used pressure treated 1x4's as baseboards; that gives me a bit of a buffer against any water that finds it's way in being wicked up into the wallboard. Also, I used gypsum board rather than plaster board, for the same reasons gypsum is recommended behind shower enclosures: it's inherently more resistant to water and mold. (I considered using fancier materials but decided this should be more than good enough.)

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    Good tip on the gypsum v plaster board. If there is significant cost difference, the board could be installed horizontally, with gypsum on the bottom for moisture/wicking resistance with plaster on top for lower cost. They should install & finish the same.
    – FreeMan
    Feb 17, 2023 at 17:46
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    I put plastic j strips on the bottom edge of wallboard to prevent wicking.
    – DaveM
    Feb 17, 2023 at 18:21
  • Thank you for the comprehensive response. Am I correct in understanding that nothing is really attached to the floor in these cases? We're just attaching to the wall?
    – Drew
    Feb 17, 2023 at 19:31
  • Thole only downside of gypsum board that I know of, outside of it being a bit more expensive, is that I think it's heavier so a bit harder to hang one-man. Didn't keep me from doing it, just took a bit more oomph carrying it around.
    – keshlam
    Feb 17, 2023 at 21:02
  • Yep. Since this isn't structural, and is being secured to something that is, it doesn't need either footer or header. Construction adhesive alone, over a largeish surface area, can support more than enough weight to hang wallboard. If you were going to hang something especially heavy/fragile on it I might suggest a few tapcon bolts to carry that weight; I did that for a somewhat overfull wood rack -- but the folks making the system I was using said that I could probably have gotten away with just construction adhesive holding their panels to the wall and lag bolts to their plastic studs.
    – keshlam
    Feb 18, 2023 at 22:19

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