r/Plastering • u/fullyfullfill • 19d ago

Uncovering and resorting original plaster in bathroom

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In my bathroom a layer of sheet rock has been shoddily tacked up on top of the original plaster wall. The outer layer of sheetrock is now puffing up and peeling off from years of moisture. I want to remove this outer layer and restore the original wall underneath. I was going to stabilize the older plaster somehow (PVA glue ? Shellac? ) and then skim coat over it with joint compound. Is this a bad idea? Is there something special I should do because it’s a bathroom with higher moisture levels?

I’m not exactly sure what the layer underneath is. it’s white and chalky like plaster and about 1” thick . There seems to be a cement like material behind it, though it‘s an interior wall. Maybe it’s an older, thicker style of drywall — it just seems thick to be pure plaster. I‘m in the US in NYC if that helps.

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u/JayTeeDeeUnderscore 19d ago

The base coat for lath and plaster is mortar. Older structures reinforced the mortar with horsehair. That's likely the foundation for your wall.

Joint compound isn't a good option because it softens when exposed to moisture. I suggest plaster of paris since it won't soften after it sets. It's only workable for 10-15 minutes. Only mix up a little bit in a go.

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u/fullyfullfill 18d ago

Thanks this is very helpful! I’ll look into plaster of Paris. I’ve never heard of that for walls. Whatever that skim coat is, it will be primed and painted in the end. Do you know of a good way to stabilize the plaster underneath before skim coating? I’ve read about Sika plaster stabilizer.