I'm going to take out part of an inside plaster wall where I want to put a built in cabinet. I'd would like to minimize any damage to the parts of the wall I'm leaving in place. I've never had to do this in plaster, and am unsure of what would be the best approach for cutting out the plaster---rotozip? sawzall? Anybody have any suggestions?
thanks in advance.
david
ps. the house was built in 1936 and the plaster is not on wood lathe, but on strips of a 2' x 8' pressed material-- looks sort of like 1/2" compressed cardboard-- that was nailed to the studs.
Roto-Zip or circular saw, set depth to a hair more than the wall's thickness. Maybe use one of those diamond impregnated blades (HF el cheapo would be fine) to prevent "tear out" of plaster beyond what you intend to trim out with the cabinet face.
Messy for sure, but probably the smoothest cut you'll get.
Sawz-all would be quick and dirty but... Might find a surprise lurking in the wall and I'd also worry about tearing up the plaster too much.
Saws are messy. Power saws are *very* messy, and the vibration they produce will damage the plaster.
Plaster walls are built in two layers: the inner rough plaster (browncoat) and the finished surface (whitecoat). If you make a clean cut in the whitecoat, you'll have a nice-looking opening, and it's not quite so important to make a clean cut in the browncoat.
So here's how I've done it: mark the outline of the opening with a pencil. Using *light* taps, score around the entire opening with a hammer and cold chisel. Repeat as necessary, scoring a little deeper each time, until you've cut all the way through the whitecoat. Now cut through the browncoat; best to do this in a couple of stages. You can hit the chisel a little harder now, but don't get carried away. When you've cut all the way through the browncoat,
*then* it's time to get out a saw, to cut through the lath. (The stuff you have is still called "lath" [not 'lathe' - that's a tool] even though it isn't wooden strips.) It takes a little practice, and a little patience. This is not a fast method of making holes in plaster walls. But it is IMO the *best* method: damage to the wall is minimized, and the dust generated is pretty much confined to the area directly below the opening.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
No matter how careful you are, you will still have to patch it. Use a (left blade) circular saw with a blade designed to cut plaster/concrete. (most dust) Or a sawzall (least dust).
Caution: Have someone hold a shop vac near the rear to collect most of the dust. Houses built in that era frequently had asbestos fibers in the plaster. Protect the other areas of the house from dust contamination. Where protective clothing and a respirator. A simple dust mask will not provide adequate protection.
Dave
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Ditto the circular saw to score the outline and then break up the portion to be removed and pull it off in chunks. Dirty, dusty but is the absolutely safest way to ensure that you won't crack the surrounding plaster - also one of the easiest ways to cut a straight line. Haven't tried a roto-tool but have failed at the sawzall route and then went to the circsaw.
Rotozip. Get the carbide cutters and make sure you have spares because you'll likely break one or more. This is the sort of thing that it's made for and nothing else I've tried works nearly as well for the purpose. Also have a good vacuum with a HEPA or other fine-particle filter handy because there's going to be a lot of very fine dust.
I've done this with both a circular saw and a sawsall and my preference would be the sawsall with a metal-cutting blade. The circular saw is fast and efficient, but will spread dust to heck and gone. The sawsall will still make a mess, but not a bad a one. Use a metal-cutting blade because it will handle the abrasive plaster better (you will probably still wear out a couple of them) and the fine teeth won't grab as much and cause as much vibration in the rest of the plaster, which would create a fresh set of problems.
Watch out for wires, etc. in the wall.
-- "We need to make a sacrifice to the gods, find me a young virgin... oh, and bring something to kill"
, a 3 3/8" cordless circular saw with a very thin blade. It isn't great for a lot of jobs but I have had decent success using it to cut a fairly clean opening in a plaster wall. Whatever method you chose, it is probably a good idea to score the outline of the cut with multiple passes of a very sharp utility knife. Then you could use a circular saw, chisel, just keep going with the knife or use some combination of tools. One thing I would not recommend is a reciprocating saw. It will cut through the plaster just fine but once it is through it could catch on a piece of lath and twang it like a bass fiddle. That could crack the plaster beyond the area you wish to cut out. If you need to remove sections of wood lath from the opening, try cutting through one end with a hacksaw (finer teeth = less chance of a snag). Once you have one end free, it might be OK to risk cutting the other end with a reciprocating saw, but the hacksaw is still probably a safer bet.
It should work well. (Hammer and chisel) I have lived in countries where this was the method of choice. If it doesn't work for you I will be surprised. As Doug said it is _not_ a fast method. Patience is a necessary tool for this method. Did it myself a few times to add outlets and switches and phone wire etc. A sharp chisel is good to mark the hole outline -- especially if it is your first time.
I have had very good luck using a 4-1/2" grinder with a masonry blade, either diamond or resin. I don't recommend the diamond for metal lath, but either will buzz right through wood, composite, homosote, or gypsum lath.
The last job that I did where I had to cut a bunch of clean holes in plaster had the added difficulty of being in a room that was occupied.
I covered everything up with plastic throw away tarps and told the customer not to worry.
The existing was pretty much as you describe - half inch plaster board with brown and white on top.
I used a six inch plaster cutting blade in the Sawzall. The twelve inch was too bendy.
I needed to penetrate the wall surface by about an inch, so as not to get deep enough to worry about the wires that were inside, while still allowing the blade to not be banging around on the surface during the short part of the stroke.
I took a five gallon drywall bucket and jigsawed it so that there was about three and a half inches of cylinder above the bottom.
I drilled a hole in the bottom that would allow the blade to run free and drilled out the baseplate of the sawzall, so that I could screw the plate to the bottom of the bucket.
I drilled another hole with a lockset bit (about 2-1/4"), above the hole for the blade, and then taped on a piece of Visqueen to seal it.
I drilled a third hole below the one for the blade, big enough to hold my six inch Maglite.
On the side of the cylinder I drilled a hole to receive the hose of my shop vac.
The last step was to run some duct tape over the cut edge of the cylinder, so that the whole mess would run smoothly over the plaster.
I drilled four holes in the plaster, on the corners, for the blade to get started and outlined the cut with a chalkline, using that dayglo pinkish chalk.
That sucker worked real good.
Note:
If you are going to do a real plaster patch, you should bevel your cut when you are finished with the sawzall, so as to give a tapered line to run you white coat to. This leaves you with a stronger patch line and doesn't protrude like the shoemaker's job of mesh tape and drywall mud.
I used drywall mud on these but added some plaster of paris, so as to leave a harder finish and make the mud set up quicker.
Enjoy.
As always, YMMV.
Tom Watson - WoodDorker tjwatson1ATcomcastDOTnet (email)
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