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I purchased two large sheets of drywall for my garage ceiling and to patch some large holes on the wall. I installed wood strips to support the drywall patch. Everything went smoothly until I test fitted the new patch. For some unknown reason, the new patch is about 1/16 to slightly more than 1/8 thinner the the old patch, creating a noticeable inset. The edges are not flush anywhere around the patch.

I encountered this problem before when I used 1/2" instead of 5/8". I made sure to get 5/8" this time. I went to the trouble of measuring the thickness with a caliper and the new was 5/8" and the old was .647. I do understand that drywall is slightly tapered on the edges. I also went to the trouble of screwing down the drywall edges of both to ensure they are seated correctly. The finish on the old drywall cannot account for the discrepancies in thicknesses. What gives and how do I level it out without making a big huge mess?

EDIT:

Turns out the sheetrock is the same thickness, but the studs are not straight. I realized that the sheetrock screwed to the laths was on the same plane as the old drywall, but the ones screwed onto the studs were off, sometimes significantly. I really need to get out of the woodworker and machinist precision mentality and realize construction has a much higher error margin.

  • 0.022" is hardly the thickness of a drywall knife, and definitely not as thick as most taped joints. The extra thickness on the old piece is probably just mud - tape 'er up and move on. – tahwos Jun 25 '15 at 22:51
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Pro installers will install drywall over irregular framing, which can give the impression of thicker sheets.

Drywall can be skimcoated with setting joint compound. This can be as thick as 1/4 inch, in some cases. Originally, the skim was done with plaster

In any case, you should fill with a setting compound mixed a bit stiffly and taper out 12 inches for a invisible joint.

  • How about taping the joints? Do I skim coat the entire surface before applying the tape? how can tape be applied if the edges are on different planes? – user148298 Jun 25 '15 at 0:50
  • @user148298 Nah, tape the margin of the patch, then skimcoat it. Just use enough joint compound under the tape (and press plenty of it into the narrow gap around the edges of your patch) to get it thoroughly set in mud, put a decent layer of mud over the tape, let it dry, then do the skim coat. It'll take two or three applications, since the joint compound will shrink each time and make the patch slightly concave. – Craig Jun 25 '15 at 4:35
  • @user148298 if the difference is 1/4 inch or under, tape then mud. If greater, level it out with hot mud, then tape. I prefer the open mesh fiberglass tape for this. – HerrBag Jun 29 '15 at 13:17
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Shim with cardboard to bring your new piece flush. Or use a ton of mud.

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    Using cardboard to back drywall may look fine when you complete it but the seams will crack the first time anything puts pressure on it. – James Jun 25 '15 at 15:39
  • Drywall shims are made out of card stock. How do I hang drywall where the wood is uneven? – Mazura Jun 26 '15 at 0:04
  • @James -- just to be very clear, I'm not talking about corrugated cardboard. As Mazura mentioned, it's something akin to card stock. – Aloysius Defenestrate Jun 26 '15 at 2:17
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As others have stated, you can basically mud the difference. I'm new to home repairs, but if I'm not mistaken you have to mud anyway right? The seams between the new patch and the old drywall have to be taken care of somehow.

You can't really use pre-mixed joint compound , because it's a ceiling and that stuff is too thin; it will fall down on you and I've personally only used it on the wall, not ceiling.

I went through this recently (Having to patch a few holes in the ceiling in my new to me home), and I paid a pro to do it and he used 5 minute mud after drilling in a drywall patch.

I don't know if this was the exact product he used but it was something similar... i.e. it's not pre-mixed. You have to add water and mix it to a thick compound. You also have to be quick because it literally dries in 5 minutes or shortly after. (i.e. can dry in your tray).

http://www.acehardware.com/product/index.jsp?productId=12789433&KPID=12562674&kpid=12562674&pla=pla_12562674

Hope this helps.

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    You definitely can use pre-mixed joint compound on the ceiling. ;-) – Craig Jun 25 '15 at 4:36
  • @craig While premix is frequently used to embed tape, its very inferior to using a setting (hot) joint compound as the first, embedding coat. After that, premix is an easier sand for subsequent coats – HerrBag Jun 29 '15 at 13:21
  • ...which you can still use on the ceiling. ;-) – Craig Jun 29 '15 at 17:49
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If your wiling to change the look of your ceiling, you could tape the seams like you normally would, and skim coat and texture the whole ceiling with a heavy nap roller, then knockdown the peaks with a spackle knife. That would camouflage any inconsistencies in thickness if you did it with some finesse...

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There are some great answers here, but I found the solution to the problem or rather avoiding the problem altogether. I want to document it so others can learn from my mistakes.

If you are going to patch drywall, the thing is to cut a patch such that the studs are revealed. This presumably will give you something to screw the drywall to. This however, is wrong. The drywall patch will often not sit flush with the existing surface.

The main reason is that the drywall sags over time and it pulls away from the stud. Also, the studs are usually not level either, so the drywall bends to match the contour. This also creates gaps between the drywall and the studs. If you look at a wall, you would be visually tricked into thinking it is flat, when it isn't. Drywall installation techniques are employed to create this illusion.

The solution, is to mend the patch to the exiting drywall by screwing wooden slats around the edges of the existing drywall hole and then screwing the patch onto the slats. This will make it flush against the drywall and not the studs.

Regardless, this doesn't answer the problem once you've encountered it, but hopefully it will prevent you from arriving at the problem. I've learned to not overthink problems and there is more than meets the eye.

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