I'm installing nice new vinyl windows, and in order to maximize the glass area, I've ordered new construction windows to avoid having to set them in the existing window boxes and live with the frames taking up more space than necessary.

However, the new windows are about an inch deeper than my current awful aluminum windows. As a result, I'm going to need to cut back the drywall in the window boxes by about an inch. It's a very cramped area and I'm not sure I'll be able to get my circular saw all the way in there. Since the lumber making up the rough opening is behind the drywall, I can't use any kind of saw that needs to penetrate through the other side by more than half an inch, if even that.

What's the right tool for this job?

4 Answers 4


A vibrating Multi-Tool (Dremel multimax etc) will work great on this. Mark with a line and cut freehand, you can easily get within 1/8th inch.

  • This was the perfect tool. Made short work of the job!
    – iLikeDirt
    Nov 9, 2014 at 20:02

The right tool in this case is the good old fashioned razor knife. (handle with a razor blade in it). Like this: enter image description here

I suggest utilizing a strait edge to make sure you cut a good line. I personally use my 4' aluminum level.

  • You mean cut all the way through with that? I've used a razor knife to score and snap drywall, but haven't had much luck cutting all the way through it. The blades dull really quickly. Am I just using bad blades or technique?
    – iLikeDirt
    Sep 2, 2014 at 19:23
  • 2
    Yes, it may take a few blades admittedly, its not you, they do go dull fast.
    – James
    Sep 2, 2014 at 20:26

If you happen to have one, or can get one cheaply, a rotary drywall "saw" or cutout tool (more like a router, really) will do everything but the extreme corners quickly and easily (and very, very messily/dustily - a shop vacuum is highly recommended as well.) Depending how many windows you have to do, it might or might not make sense - or your local tool rental place may have one for a reasonable rate.

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A tool where buying the most expensive one does not make sense - they live a dusty life and will expect to die from it, so if you can rent one or find a cheap knockoff to buy, if might be sensible... Otherwise, the knife is a cheaper tool and gets all the way into the corners.

  • While this tool is great if there is a fairly rigid edge that defines the extent of the cutback on the drywall. It works in electrical boxes and if the framing is exactly as far as you want to cut back. It's not clear to me from OP's description that the existing framing is the exact size of the cutback.
    – bib
    Sep 2, 2014 at 19:24
  • 1
    You can use them with a fence guiding the base, or by eyeball with a pencil line (do use safety glasses in any case, of course.) I've never actually used mine in the "pilot on something behind" mode. YMMV.
    – Ecnerwal
    Sep 2, 2014 at 19:47
  • I tried one of these (a nice DeWalt model) and had disastrous results. Compared to the multipurpose tool, the cuts were slower and messier. And the included bit snapped after 15 minutes.
    – iLikeDirt
    Nov 9, 2014 at 20:02

You are never going to cut it perfectly enough to just drop the new windows in and then have the dry wall look nice. I recommend completely removing the drywall and corner bead. After the new windows are in, use wood to trim where the drywall was. Half inch boards, ripped to the width need to go flush between the window and wall. And then window casing to cover the gap from from wall to trim. Caulk and then paint.

But something to think about... water proofing those new windows. When you use new build windows in a retro fit job it is going to be hard to place the weather seal strips over/under the nail fin of the new window. And if you don't weather proof, the next rain you get on those new windows you will have water enter your wall.

  • I'm cutting back the stucco 6" or so on the outside, properly applying waterproofing membrane, and integrating it all properly with the tar paper.
    – iLikeDirt
    Sep 2, 2014 at 19:41
  • Only saying this, since I had this issue once in a house I lived in. The builder didn't to the weather proofing correctly and had buckets of water coming to the house/walls from one window group.
    – diceless
    Sep 2, 2014 at 20:41
  • That's why I'm doing it myself. :) Having heard such horror stories from many other people, I'm pretty sure I care more about keeping my own house dry than most of the contractors out there do.
    – iLikeDirt
    Sep 2, 2014 at 20:44
  • 1
    I do recommend using wood to trim out the windows. It's more costly in supplies that dry wall but much quicker and a lot less dust when installing. Also when done, it adds a lot more character to the windows. But if you really want to cut the dry wall, an oscillating tool is really going to be your only option.
    – diceless
    Sep 2, 2014 at 20:55
  • I like the wood idea!
    – iLikeDirt
    Sep 2, 2014 at 21:51

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