Gypsum and lime plaster

[Liz Gauntley]

Hi, Im not a plasterer but need help from experts. My newly renovated, limestone 18century cottage has badly cracking plaster. I believe gypsum ( pink plaster dust) has been used on the limestone outer walls. I cannot strip the plaster so would it work to skim the cracks with lime plaster or would it just crack again due to incompatibility. Thanks in advance.

 

[Dropsalot]

Sorry liz.........
I really am......as with all things worthwhile, there is unlikely to be easy shortcut.
In the short term a filler might help you, but you are correct to say that gypsum and lime are not good together.

 

[t33ch]

Hi, Im not a plasterer but need help from experts. My newly renovated, limestone 18century cottage has badly cracking plaster...

Unfortunately it needs to come off.
I guess that it is solid walls? Gypsum just isn't moisture tolerant enough for these sorts of properties.
Most likely the gypsum will keep degrading and blowing out whatever you put on top.

Don't be tempted to use damp proof/sealant type paints over the top as it will make matters worse.
Short term you can fill and paint with lime based/breathable coatings, but it isn't going to last.