I read that old plaster walls can have a lime content over 50%

I was looking into patching a crack in my 1920s house and found a study from the University of Pennsylvania. It said plaster from that era can be more than half lime by weight, which is why it sets so differently from modern drywall mud. I had no idea the material was that different. Has anyone here had to match or repair really old plaster successfully?

2 comments

2 Comments

bailey.sandra24d ago

Exactly, modern stuff crumbles. I had to use that same NHL lime mix to get a patch that would last.

martin.tyler24d ago

Yeah, that lime content explains why it cures instead of just drying. I ended up using a bag of NHL lime plaster from a specialty supplier, modern stuff just crumbles next to it.