I found these "boards" under the wallpaper. They feel different from drywall, smooth and cold to the touch, kinda like a tile or ceramic of some sort. What are they? Can I plaster over them to have an even surface for painting?

Board 1 Board 2

  • Looks like something once intended as an access panel...?
    – keshlam
    Feb 19, 2023 at 13:10
  • @keshlam It is just a pattern printed on them. They're a solid slab.
    – MKII
    Feb 19, 2023 at 13:57

2 Answers 2


I'd say go ahead and try putting a skim coat of plaster over it and see what happens. At worst, you try again...

For large areas of plaster repair I've become fond of using plastic window-screen material as a support/reinforcement matrix. Same idea as the mesh tape used to help bridge and stabilize cracks, but over a larger area.


It's difficult to say if plaster will stick to it without knowing what the boards are made of.

However there are several different parts with gaps between them, so if you just apply plaster it will most likely crack where the gaps are.

If the extra thickness doesn't bother you, I'd recommend getting a sheet of drywall: cut it to shape, fasten with drywall screws or appropriate fasteners for the material. Then you only need to plaster the edges, and you'll get a nice smooth finish.

If the extra thickness is a problem, you can apply untextured fiberglass. I don't know how it's called where you lived, so I'll describe it: it's sold as a roll, looks like thick hard white wallpaper but if you look closer you can see the fibers. It's usually available with or without texture.

The point of this is you can glue it to the wall with a compatible adhesive, and it will smooth over the gaps and cracks, and the cracks will not come back. It's not difficult to make an old crusty wall look nice with it. Then you can either apply a thin coat of plaster for finish, or just paint it.

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