6

I was removing some old vinyl wallpaper from a kitchen and I ran into a couple of patches of mold behind it. The one area was due to a leak in the upstairs bathroom and the other was under a window. Both issues have been taken care of.

However, even though I cleaned the mold from the drywall with an appropriate cleaner, I felt better removing the drywall and need to replace. My problem is trying to make a clean cut line on the drywall that is in front of wood as seen in the photo.

I can’t use a drywall saw because of the wood. I’ve been looking at rotary cutters, etc., but I don’t know what would be the best to cut the drywall out square to proceed with a patch without cutting the wood studs behind.

existing situation

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  • 1
    My first thought is a Dremel.
    – Sam Rueby
    Jul 17 at 2:40
  • 2
    A drywall saw, held parallel to the board. Having a good one helps. Mine's so sharp that I carry it in a sheath. A crappy one will work (it's only gypsum), you'll just wrack your knuckles more.
    – Mazura
    Jul 17 at 17:33
  • 5
    Whatever tool you use, a useful tip is to cut both at once, or at the very least, cut the patch first, then draw around it - either of these methods is better than trying to cut a patch to fit a hole that inevitably isn't quite square. Jul 18 at 18:19
  • 2
    What's wrong with a utility knife and something to use as a flat, straight edge (like a ruler or level)?
    – TylerH
    Jul 19 at 18:03
  • 1
    Agree with @TylerH, utility knife/box cutter is what I would use, especially for such a small cutout.
    – Glen Yates
    Jul 19 at 18:37
34

You want an oscillating tool. Fein made it first, but everybody has one now. If your battery platform of choice has a model, go battery. If not, there are plenty of corded ones out there.

As an example: enter image description here

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  • 8
    if you hold the patch onto the hole, you can use it as a template and trace it with the above type of saw for an easy perfect fit; the patch need not even be particularly square...
    – dandavis
    Jul 17 at 7:47
  • 4
    This tool is absolutely amazing to use. The precision it gives you and the ease of use is superb. The main downside I heard is the blades dull relatively quickly, so it might help to learn how to do basic tool sharpening.
    – Nelson
    Jul 18 at 5:39
  • 4
    +10 if I could - this has been my only drywall cutout tool since using one for the first time over a decade ago. There's nothing else that works as well.
    – J...
    Jul 18 at 6:36
  • 9
    I recommend holding a shop vac hose under the hole with your other hand (or with a helper) while you cut to significantly cut down on dust. Not only will the dust get everywhere in your house otherwise, but it will also get into the tool and can make it overheat and significantly shorten the life of the tool. Jul 18 at 15:39
  • 5
    You want an oscillating tool - amen. Even if you don't realize it now :) - use this as an excuse to get one; very handy
    – Caius Jard
    Jul 19 at 15:12
21

Hmm some options... A Dremel or rotary tool can be set up as a drywall cutout tool, which is a single purpose version built for hard use. Because of the wood backing, you need cutout bits with flutes right to the end so you can set it to the correct depth and not have too much interference with the old wood behind. Just cut straight lines and you're good.

Don't want to spend $50 on tools? A common utility knife cuts most types of wallboard. Just use a straightedge to start a straight cut, then apply pressure and draw the knife over the cut over and over until you're through. A little tedious, but for one job, takes less time than going to the store to buy a cutout tool. To get right close to inside corners, you may be stuck with this method.

Other popular options would be a keyhole saw, which you don't want because it requires an empty space behind the wallboard, and a circular saw, which is popular for long cuts to specific depth. Note that a circular saw should not be used on steel stud because if you screw up the depth you will ruin the integrity of the stud, whereas with wood framing this is not a concern. Note that this technique is typically used cautiously in case of a wire too close to the face of the wall or similar. If you have half inch wallboard, you can set the saw to 7/16 and pass a utility knife to finish.

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  • 2
    Cutting drywall with a circular saw makes a lot of dust. A utility knife is the tool to use but keep your other hand well away from or behind the knife. Jul 19 at 14:41
  • 2
    A utility knife can be hard going if you're not in a position to snap the board but repeated scoring will work. Amen to using a good quality metal bodied knife; I've had the back end of an exacto blade come through the plastic handle and into my finger before now.
    – Caius Jard
    Jul 19 at 15:09
  • 1
    @JimStewart is correct about dust production. Same applies for cutting drywall with a rotary tool. I'm an electrician so score and break is rarely an option for me, but repeated scoring, although tedious is functional, even for smaller folks. I've never tried with a full plastic bodied knife because metal bodied knives are only marginally more expensive, but it's good to be aware of the limitations of your tools. Does this feel like hard use? Is the knife I bought intended for hard use?
    – K H
    Jul 20 at 3:04
13

for a clean cut, really a craft knife is the only tool that can deliver.

Saws and powertools will leave the edge of the paper rough. Not that you couldn't use a power tool. but powertoos makea lot of dust and afterwards you'd need to clean the edge up by trimming with a knife.

For a short cut like pictured, I'd just carve a v groove in the drywall with the knife until I'm through then tidy up the edge.

10

Obvious cheap answer is a craft knife - cut along a steel rule for a straight edge. It's a slow job but it'll do. Or faster using a broken hacksaw blade in a handle designed so the blade sticks out a couple of inches.

Or use a jigsaw with a shortened blade that will just miss the wood at the lowest point of its stroke.

Make certain there are no wires or pipes behind where the cuts are to be made.

1
  • 1
    Agreed - no need to buy more power tools. Presumably OP will patch and plaster the hole as well, so realistically anything sharp will work, and time is less important than doing it right.
    – Criggie
    Jul 18 at 8:24
3

The best tool for the job as Aloysius stated is an oscillating tool.

If you are on a budget or just want to cut one or two holes, a jab saw (often called a drywall saw) is your best bet (Example picture below).

enter image description here

2
  • Will this work with the wood right behind?
    – Tim
    Jul 19 at 20:14
  • @Tim It'll make it more of a chore but the gypsum is so much softer than the wood that you can still do it. The jab saw isn't going to be able to hurt the wood without a huge amount of intentional effort. Jul 27 at 9:16
2

I use a RotoZip (https://www.rotozip.com), because it plunge cuts to exactly the depth of the drywall without cutting into anything behind it. It can also accommodate a shopvac to collect the dust. I cut right down the middle of studs, making it easy to screw in a replacement piece flush with the original sheet. It has a clear shroud and LED illumination making it easy to follow the lines you've drawn on the wall. I am just a homeowner -- not a pro -- so I only use it once a year or so, but I still feel it's worth the cost.

1

I do love the oscillating tool for this but if you are on a budget utility knife and elbow grease will do. I wouldn't worry about making a perfectly straight cut or patch since you are going to use drywall compound to fill around it anyway and too tight just makes a weak joint. You're fortunate you have all that wood in behind to screw the patch too.

Hint: For an invisible patch, I cut-and-peel the paint around the outside patch area to look like a picture frame border. It gives me some area to place my drywall tape (or mesh) without bumping out. Might not work on all walls if the paint is thin buy my old house had 50 old coats so it pealed easy. If you don't do this at least chamfer the edges. Wet surfaces with a brush before applying the patch compound.

0

Mini hack-saw (if that's the general name) + straight edge:

https://www.amazon.com/Capri-Tools-12-Inch-Mini-Hacksaw/dp/B0791WKFQ9

enter image description here

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