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While preparing to mount a bracket for some shelves, I attempted to use a stud finder to locate studs. The device reported four areas as studs, but curiously they did not run vertically. I was expecting to find vertical wooden studs, but these four areas were surrounded by non-stud space on all sides - and the “tap test” confirmed them as solid while all around them sounded hollow.

The four areas were arranged as the corners of a square, about 14 inches on each side. The areas themselves were two or three inches in diameter - hard to assess their exact shape.

I decided to drill into them to investigate - about 2 inches deep. The drill came out covered in white powder, as if I had just drilled through a particularly thick piece of drywall.

Why would there be thick plaster at these points, and no apparent studs in the rest of the wall?

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  • Is this an outside wall or an inside wall? An inspection camera might come in handy.
    – crip659
    Aug 29, 2023 at 10:23
  • It’s an inside wall.
    – jl6
    Aug 29, 2023 at 11:00
  • Drywall/plaster do need a support wall to hold them up, studs,blocks, something. Did you check the rest of the wall for similar stuff? Does the wall seem thicker than other walls? What is on the other side of the wall and does seem the same(lack of studs)?
    – crip659
    Aug 29, 2023 at 12:06
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    It could be a lath and plaster wall covered with sheet rock. Maybe someone decided it would be quicker, cheaper and faster to cover it rather than deal with smoothing a cruddy looking lath and plaster wall. Aug 29, 2023 at 13:33
  • Is it a party wall (an interior wall but separating two dwellings in the same building?)
    – Ecnerwal
    Aug 29, 2023 at 14:10

1 Answer 1

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Sounds like you're dealing with plaster and lathe walls, which are very thick!

When you hear the stud finder going off, it could be a stud - but it could also be the lathe too. Change your stud finder to the 'deep' setting if you have it.

Older homes' walls were 1st studs running vertically, then 1/2" thick lathe running horizontally, and then covered with who knows how many years of plaster. I'm sure it's a minimum of 1" thick.

Because of the amount of thickness, we can add it up to get to an approximate stud depth.

1" of plaster (or more) 1/2" lathe 1" into the stud

That's a minimum screw size of 2 1/2" to reach the stud. It could be more though, I will sometimes use 3" screws to be safe.

If you have more questions let me know, try to attach a photo so I can reference things for you better!

  • Joe

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