This is an interior wall in a bedroom closet in a house built in 1940 in the northeastern US. I suspect that the material is not typical drywall from other experience hanging things on other walls in this room (a threaded drywall anchor doesn't bite into the material), but on the other hand I don't see any sign of wooden lath anywhere.

The stud is 1 inch behind the surface of the wall (lighting is poor here, used a flashlight to help):

hole drilled into wall, 1 inch to stud

and here is what the debris from drilling into the wall looks like:

debris from wall from drilling, on floor

Can you have plaster this thick without the wooden lath material to support it? Or if this appears to be drywall, was this a more common thickness back then (I know 1/2 inch and 5/8 inch are common now in the US)?

  • From the first picture, it looks a little bit like there might be two distinct layers. People sometimes put a second layer of drywall over an existing layer, so it could possibly be two 1/2" sheets of drywall.
    – negacao
    Oct 12, 2023 at 19:31
  • Is the material in the hole hard or seems to have some give to it? Wondering if it is some type of foam board.
    – crip659
    Oct 12, 2023 at 21:09

1 Answer 1


Hard to tell from the pictures, but it could be rock lath plaster. It ends up looking like someone put coarse plaster over a gypsum board then finished with fine plaster, which is basically what it is. No wood or metal backing.

I know it was around in the 50s and in the northeast. It's basically applying plaster over gypsum board instead of lath. Eventually it evolved into drywall.

Here it is on InspectAPedia.

  • Please remove your duplicated comment-answer.
    – isherwood
    Oct 13, 2023 at 20:32
  • I’m convinced this is it. Thanks!
    – matt b
    Oct 14, 2023 at 23:57

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