White, Crumbly Layer Under Mortar and Tile- what is it?
+1
Any idea what this white crumbly layer is? I removed a tile - the grey hue on top is the mortar, but the white crumbly part I'm not sure of.
We had each layer tested for asbestos - all were negative except for the linoleum. The wood-looking layer appears to be in good shape and this white crumbly layer lifts pretty easily. It kind of reminds me of drywall.
House built in 1961 if it matters.
I'm guessing, since it looks (and apparently behaves) like gypsum, that it is some kind of drywall material. It may have been used for leveling or soundproofing or maybe something to protect the wood from the mortar.
looks like plaster board
I agree it looks like sheetrock.
It's early Sheetrock. In its early form Sheetrock was installed in long planks then skim coated with plaster to fill in gaps and make it look Nice.