3

Can I skim coat a painted interior concrete block wall? If so:

  • What can I use to prepare the wall?
  • What material should I use (joint compound, plaster, other)?

All DIY so simpler the better.

  • What are you trying to achieve? – Tester101 Mar 8 '16 at 16:54
  • @Tester101 -- Just a finished looking wall. – Jagra Mar 8 '16 at 17:12
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Is the wall dry? is the paint in good condition? If it is dry you could use joint compound. If the paint is pealing it would need to be scraped first. I like using mortar on block walls because it holds up to moisture better than joint compound but have not used on painted block. Some don't like mortar because the sand is very rough even after painting.

  • Fully interior block wall. Dry. Paint in good condition. No pealing at all. Do you think I need any prep coat before joint compound? – Jagra Mar 8 '16 at 16:06
  • 1
    roughing up the paint will improve adhesion. Usually block that is painted still has enough small pits to hold joint compound quite well. Clean and free from dust and grease is the biggest thing to work on. – Ed Beal Mar 8 '16 at 18:57
  • +1 - if it's an above ground exterior wall, in good shape - wash it really good, prime it, and skim away. Just keep your coats thin, to help "screed" successive coats, in order to minimize sanding. Use a WIDE knife. You may also find yourself knocking down mortar lumps, with a hammer. – tahwos Mar 10 '16 at 1:06
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Why not simply glue 1/4 inch drywall to the block and just compound the joints? A few concrete screws can be used to hold the drywall in place until the glue dries, or just use a few 2x4s horizontally across the middle with an angled brace to the floor until the glue sets.

  • This is worth considering, especially if we're talking about a relatively large wall. Full skim coating is tricky and it takes some practice (and a lot of sanding) to get a decent result. This approach would reduce the amount of mudding/sanding needed overall, and the 1/4" with glue would be well supported on a block wall. – Shimon Rura Mar 9 '16 at 2:35
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Just wrap a layer of 48" fiberglass stucco mesh (I would use 2 ounce mesh) across the whole face and mud away. It goes pretty quick and it will be good and strong so it doesn't crack over time.

0

The simplest solution to get a smooth wall is to attach furring strips to the concrete and then drywall to that. You'll spend a fraction of the time and have a much better resulting look than trying to skim coat the entire wall and hoping for good adhesion. If this is a basement with the potential for moisture, then make sure to use materials that will not mold (they make special paperless drywall for that).

  • Unfortunately, no room for furring strips and sheetrock. Not a basement. No moisture problems. – Jagra Mar 8 '16 at 17:11

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