I'm putting in a new bathroom cabinet, and the hole is 1 3/8" too large on both top and bottom, and 1/2" too large on both left and right. What type of lumber or cut would I use to shim this?

The existing hole is surrounded by 2x4's on all sides (studs and whatever the horizontal version of studs are). My plan was to just cut pieces of the right size and nail them to those.

  • Note that you might want to consider using metal or plastic pieces.
    – Hot Licks
    Dec 19, 2020 at 19:38

4 Answers 4


You could use almost any wood that happens to be the right thickness. Multiple pieces even - e.g., multiple layers of plywood.

However, I would definitely use screws rather than nails. Nails will hold just fine, but I find that screws with a decent battery-powered drill/driver are a lot easier than nails, especially when working in relatively small spaces.

  • 2
    Also screws are easier to remove if you change you mind for any reason.
    – Bonzo
    Dec 19, 2020 at 19:53

If your hole is 1-3/8" too large on both top and bottom, then the hole is 2-3/4" too big.

Throw a 2x4 in there to take care of 1-1/2" of it on the top, then fill in 1" with some plywood (2 layers from 1/2" thick plywood would do the trick). Now you're left with a 1/4" gap which you'll want so that you've got room to run a few shims in to ensure that it's nice and level.

1/2" too wide on each side is 1" total too wide. I'd use another strip from that 1/2" plywood on one side and a few more shims to hold it nice and plumb from the other side.

i.e. Unless the hole is exactly centered on where you want the cabinet to be centered, it's OK to fill it unevenly for your maximum convenience.

  • 1
    Yeah, good point and as another replier said, not having it centered means less drywall patching too. Dec 18, 2020 at 18:47
  • Note, @Tumbleweed53, that none of this lumber needs to be particularly pretty wood. It just needs to be solid enough to hold a few screws...
    – FreeMan
    Dec 18, 2020 at 21:04

That will work. The main thing is to make sure that the pieces you put in are sized properly and securely attached. I always prefer screws rather than nails but it's up to you.
In cutting the shim pieces you need to decide if you want to shim all four sides or just one side and possibly top or bottom. This will be determined by the surrounding drywall (you don't want to have a gap between cabinet and drywall) and how important it is to you to center the cabinet in the opening. So, if the spacing works you may only have to shim one side and possibly top or bottom. Most cabinets I've installed only have mounting holes on the vertical sides.

  • 1
    Actually this is a good point. I had planned on shimming all 4 sides, but that leaves 4 sides worth of drywall patching. I could just shim 2 sides and then have to patch drywall on just 2 sides. Thanks. Dec 18, 2020 at 18:46
  • 1
    Thanks is good - an upvote is better.
    – HoneyDo
    Dec 18, 2020 at 20:33

A tip for your consideration is to use 2P-10 (which is a 10-second 2-part adhesive) or something similar to bond your shims in-place before screwing them. The idea is that you’d cut your shims to size, figure out exactly where you want them, then spray the activator on one part and put a couple of dollops of the adhesive on the other part, and then put them together. Be careful as they’ll bond INSTANTLY, so you don’t have to hold them in-place. 2P-10 comes in 4 different viscosities. Get a sampler pack. You’ll use the snot out of it and buy larger bottles of the stuff you use more often. I do woodworking as a hobby and like the gel and heavy products. Check out FASTCAP — they have lots of ingenious solutions.

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