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Paint started flaking off a small portion of a recently painted wall (replastered entirely), I assume this is because we failed to apply the mist coat properly.

We did apply a mist coat, but might have missed this area a bit...

What is the best approach for this? Remove flaky paint with scraper, sand down, clean and reapply mist coat + extra layer of paint to affected area? Trying to avoid this happening again!

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  • That looks like a moisture problem to me. Is that a possibility? – isherwood Mar 19 '20 at 14:25
  • I figured out what a mist coat is. That seems like an obsolete technique. Use drywall sealer or proper primer. – isherwood Mar 19 '20 at 14:41
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I am not sure what a mist coat is but it looks like there was dust that kept the mud or paint from sticking. If you had used a skim coat of mud without cleaning the surface as it dries it can flake off. The same is true on top of the mud--if it's dusty the paint may stick to the dust and flake off when dry, so in both cases a good wipe down is needed to prevent these kind of problems.

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If that uneven texture in the first photo is paint lifting up, then I don't believe it was caused by a missed area of mist coat. A severe reaction like that is more likely to be surface contamination under the paint or something wiped onto the wall after painting.

It's interesting that the problem occurs on both adjacent faces. Maybe there is something happening on the other side or the inside of the wall.

Other ideas:

  • Plaster still damp when painted
  • Water leak
  • Wax or oil on the plaster, check if water spray soaks in or beads up

I've had success cleaning off light surface wax/oil with white spirit followed by methelated spirit.

After fixing the source I would be thinking about a light sanding then sealing it with a couple of coats of shellac primer such as Zinsser BIN. Smooth any remaining unevenness with fine surface filler, light sand and then paint.

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