My half bath rough in is under the staircase. The original builders put an angled side of the ceiling. I tried hanging a piece of drywall but I'm not super happy with the result. The right side sticks out too much.

Would a prefill layer of (hot?) mud run on each edge fix this? Would normal taping fix this? Or should I take it down and start over? If I need to take it down, would hanging a plywood backer first help?

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  • I would not use a heavy fill especially under a stairwell this would invite cracking. In cases like this I cut shims to fill the uneven spaces.
    – Ed Beal
    Sep 2, 2017 at 19:22
  • When you say shims, do you mean behind the drywall board?
    – Chris
    Sep 2, 2017 at 19:32
  • That's a 1/4" of fill, on 8" exposed stair section. That's nothin. Just fill it.
    – NPM
    Sep 2, 2017 at 21:24
  • Yes shims, I have made archwayss using angled cuts and shims with only topping mud. Last much longer. Stairways are known to have cracking issues because of the vibration of people walking the stairs. Less is better in this case.
    – Ed Beal
    Sep 2, 2017 at 22:23
  • Chris, don't leave us hanging. Please follow up with this.
    – isherwood
    Apr 30, 2019 at 13:09

2 Answers 2


Prefill will take care of it. Prefill only enough to effectively get tape up there, then begin buildup. Feel free to go a little heavy, sand, go a little heavy, sand, etc.

Just remember though, hot mud only dries quickly on the surface, just enough to lightly sand and recoat. It's still wet underneath, so don't go too thick per coat, and make sure you give it a couple days dry time before priming and painting.


NPM is right, but first you need to check whether the resulting corners will be parallel. Even the best tape job looks like ick if you end up with a trapezoid.

Lay a sharp-cornered straightedge on each plane and mark where it intersects with the other plane. Do this for both intersections. Then, measure between marks parallel with the staircase. If it's more than 1/4" out I'd shim as needed to straighten things up.

I highly recommend pre-bent corner tape (with the metal strip embedded). Inside corners are very difficult to get straight, even for the pros. You many need to adjust the angle somewhat.

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