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There's a wall in this attic room in my house where a wall-mounted lamp and its switch were mounted on. Recently I had the lamp removed in favor of a better lighting setup and the switch relocated to a newly-installed drywall. The drywall was painted during the installation but there was further work left with the electrical so that part was left for later. As a result I'm currently left with this wall (note - it is not drywall, it's one of the faces of a reinforced concrete pillar) that has two plastered holes in it:

Image of full wall with both holes

I have more of the exact color of paint that this wall is painted in, and want to paint the wall myself to gain some experience (it's small and its location is inconsequential). I think I can handle the painting part but I'm not sure about the prep:

  • The top hole is covered with plaster, there's some leftover plaster in the area surrounding it and overall this stuff (including the hole repair) is protruding a bit from the wall. Top hole close-up

  • The bottom hole has the opposite issue - it seems like the hole repair isn't flush with the wall; it's very, very slightly recessed from the edge of the wall surrounding it. This creates the look of a cracks around the repair since you can very slightly see (maybe the shadow of) the side of the wall around the repair. Bottom hole close-up

Overall, I'm wondering how I should prepare this surface for painting. Is it enough to sand down the surfaces around the repairs with sandpaper so that they are somewhat even, and then just clean it and paint it? Do I need to apply further plaster / paste etc. to make the surface flatter, and will it work when it's already so close to flat? The hardware store said paint primer was probably not necessary since we're using the same color and the repairs are not large, is this accurate?

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    Are there still junction boxes behind the new drywalling? Are there any live wires in those junction boxes? Aug 26 '21 at 20:55
  • The junction boxes were removed. There are still wires in the wall but they are not live.
    – cgokmen
    Aug 27 '21 at 7:33
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It's unlikely that is plaster but rather appears to be drywall compound. Of course you can just paint it as it is but it will look messy.

The usual approach is to fill and sand to get a smooth surface that is flush with the surrounding drywall. For those of us who don't finish drywall for a living, it can take a few cycles of compound plus sanding to get a nice finish. Thinner applications of compound are better than thicker applications.

Once you are satisfied with the finish you should wipe with a damp sponge or rag to remove any dust and then apply primer first and then paint. Follow the instructions on your primer container.

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    Note that after the (slightly) damp sponge wipe down, the wall should be allowed to dry thoroughly. Paint doesn't like wet surfaces.
    – FreeMan
    Aug 26 '21 at 13:35
  • This wall isn't drywall - it's one of the reinforced concrete pillars of the building. Should I still apply further compound here? What kind?
    – cgokmen
    Aug 26 '21 at 14:29
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    That sure looks like drywall to me. Are you sure it's not a concrete post that is clad with drywall?
    – jwh20
    Aug 26 '21 at 15:21
  • +1 for the mention of primer, it's very important to use primer, not paint (and not "paint + primer" combo stuff), otherwise the paint very well may just bubble and peel off after it dries.
    – nexus_2006
    Aug 26 '21 at 21:25
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In addition to what @jwh20 stated, matching the texture to the existing wall can be tricky. When patching up the hole, concentrate on filling in the hole, not sanding the existing area. Keep the existing area free from patching material or you'll have to texture match that area too. Most walls have a sort of orange peel surface and you can experiment to duplicate that on you new patches. I've had luck running a dry paint roller over the still wet patch or dabbing a paint brush or dry sponge with some mud on it over the patch.

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    Unfortunately, it's too late for the area where compound has already been spread far and wide. That area may need to be sanded smooth then a thin coat of drywall compound applied & textured to match.
    – FreeMan
    Aug 26 '21 at 13:37
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    @FreeMan He might be able to reduce the area a bit. Some of the compound looks pretty thin and might be able to work it out.
    – JACK
    Aug 26 '21 at 14:22
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I would rough-sand the entire concrete face to give it some tooth, making sure the two patches are level or slightly below, and then skim coat the whole thing with a finishing compound.

You might choose to embed some metal corner reinforcing on the very edge to help prevent chipouts as people walk past.

Then when it has set, smooth-sand the whole face from the door jamb to the corner, and paint it with sealer, undercoat, and topcoat. You could stop at the corner, though it might be a better job if you go around the corner too, depends what's around there.


If that still doesn't look right, I'd hang a picture frame on it, or a clock, or perhaps hand-paint a mural on that face for some personalisation.

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