While renovating our kitchen the electricians opened part of the exterior wall. It is a plaster wall with metal wire lath in a 1920s-built home, but I can't identify this darker material behind the plaster.

kitchen wall wide

material detail

material front

The electricians stopped manipulating the material and asked if I wanted to have it tested for asbestos. The testing is in progress but I'm not sure what this material is to begin with.

It does look fibrous but it is dark. It almost looks like fiberglass, mineral wool, or even cardboard, but it seems to be comprised of strips that are nailed to the studs and/or furring strips.

(The gap in the material was not cut as part of this renovation. A previous owner had bathrooms installed or updated above and below the kitchen; we think the plumbing visible in the pictures is the vent stack and/or sewer line, and the plumbers must have cut this gap in order to install it.)

  • Looks similar to "Mineral Wool Insulation Board High Temperature"
    – Armand
    Commented Aug 16, 2023 at 20:37
  • Back in the day when the house was built, that could very well be asbestos.
    – Jack
    Commented Aug 17, 2023 at 3:25
  • I'm definitely having it tested, though most asbestos seems to be light in color. I'm just curious what purpose the material actually serves. I can't figure out any reason why it would come in strips like this; if it was (asbestos) insulation I would expect a roll, sheet, or tape of some kind.
    – edaemon
    Commented Aug 17, 2023 at 4:03

1 Answer 1


I had this material tested and it turned out to be cellulose. There was no asbestos detected. I still haven't found the exact product or anything similar to it but it is almost certainly meant as insulation.


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