I cut a 12x16" access in my drywall and installed a new piece in this spot. There's a round 5" outlet/box (for a bathroom wall light) that is only about 1" in from the seam (in the new part). So now I'm in the position where this opening is close enough that the mud wants to be pretty thick to get a subtle taper from the seam. My best idea is to put a cover on the box and then excavate it later, but this seems hackish. What's the right way?

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    Why does the mud want to be thick? Is the seam not even? What is thick to you, how many 16ths?
    – crip659
    Dec 3, 2023 at 15:30
  • Can you post a pic? Dec 3, 2023 at 15:33
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    It wants to be thick to cover the tape and because it's in the part of the drywall that is thinner on purpose. You know how it tapers at the edges.
    – Mastiff
    Dec 3, 2023 at 16:17

1 Answer 1


Whenever I am doing mudwork such as you are, First I need the box to be flsh or recessed a little below the sheetrock. Code allows 1/4" but it doesn't need to be that much. The mud over the joint does not need to be thick. A 1/16" if smooth and feathered out well over 8" beyond the tape joint or more is all that is needed for sanding. Test the thickness by placing the corner of the mud knife in the smoothed out mud to govern how thick you have it. 1/8" is too much but could work. It u]just takes a long time to dry.

When applying mud, I treat the wall like the box is not there. I use my 12" knife to work the mud. The mud will fill the box if it is not covered with something. I use cardboard cut to fit on the inside of the box and the wires will keep it from going in too far.

I use fast set mud (dry mix) to do this so I can apply 2 of the 3 coats right away, needed to normally do drywall work.

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