ᐅ Lime-gypsum plaster crumbly and therefore defective?

Hello everyone,

The lime-gypsum plaster was applied in October/November (the screed and underfloor heating are still to be done). Today, we wanted to remove some outlet covers. When knocking off the plaster, it crumbles into fine powder (like falling sand). Is it normal for this type of plaster to be so soft? Even the slightest impact would cause damage, wouldn’t it? Should we have used gypsum plaster instead, or is this a quality issue? (In the bathrooms, there is lime-cement plaster, which is noticeably harder but also partly crumbly when chipped off).

Wintersonne

Well, this cannot be assessed reliably and generally from a distance. However, it does sound unusual. Are there any photos available?

1st picture: after the first two hammer strikes, which were not excessively strong
2nd picture: after more hammer strikes, the whole area starts to crumble. Or is this normal?
3rd picture: here you can see the fine crumbles; the plaster can simply be "rubbed off" at the edges (with the hammer or another hard object)

It looks quite normal in the pictures. I cannot assess whether the plaster is excessively soft.

You can already scrape off the plaster with pressure from your fingernail (picture 3), then it continues to crumble...
I'm tempted to test the plaster in our rental apartment to have a comparison, but I think I should leave it alone...
Here, the plaster has already withstood sharply shot balls without damage, so I somehow can't imagine it being the same here. But as I said, I lack the experience.

Which can’t even remotely be compared to a hammer. Especially not with a cavity behind it. You are probably confusing plaster with mortar.