Skim coating over plaster walls with semi-gloss paint on them?

Question

I want to paint my bathroom, but the walls are really gnarly and I'm trying to figure out a way to smooth them out before I paint. I live in a concrete masonry building (I think; it was built in 1910), and the walls are made out of plaster. The existing paint is a semi gloss, but there's tons of bumps and even some pretty big spots (like the size the bottom of a coffee cup) where parts of the wall have just crumbled away.

Okay, it didn't actually just crumble away on its own... I saw this section of paint peeling off the wall and I just couldn't resist the urge to peel it away, and then to my shock a chunk of the wall came off with the peeling paint. I'm VERY new to any sort of home improvement stuff. I should have paid more attention when my dad tried to teach me theses sorts of things. I have been reading/watching tutorials about skim coats, but I'm not sure what kind of material to use. Will a plaster skim coat stick to the semi gloss paint? Or is that not at all what I should be using? Any advice would be appreciated!

Answer 1

Sure, you can skim coat over semi-gloss. You just have to remove any loose paint and plaster and scuff up the paint on the entire wall with some 120-grit sandpaper first so that the skim coat has an easy way to adhere to the wall.

Also, don't expect perfection on your first skim coat attempt, this will be a big learning experience for you.

See https://solvesonic.com/skim-coat-over-paint for a longer tutorial.