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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?
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bailey.sandra7mo ago
Exactly, modern stuff crumbles. I had to use that same NHL lime mix to get a patch that would last.
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martin.tyler7mo 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.
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jackson.wesley6mo ago
Oh man, that study is wild. I saw a video from a restoration guy who said the same thing, that old plaster basically turns back to stone over time. He showed a patch done with modern joint compound and it was all cracked and falling out a year later. The lime lets it breathe and move with the house. Makes you realize why those walls have lasted a century.
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