Best way to cut hole in plaster?
I need to cut a hole in our plaster ceiling so a plumber can determine the source of a leak from our bathroom (about 4'x4'). I am sort of handy and figured I can cut the hole myself to save a few bucks (plumber won't cut hole). At first I was going to use a reciprocating saw to cut the hole, but then thought it could damage the floor joists if I cut to deep. Anyone have any recommendations on the best way to cut the hole?
Here's what I've done. You want to get the plaster off the lath first, so score the area of the cut with a utility knife (you'll dull the blade, but keep going), you want to prevent chipping. Once the area is outlines, chisel out the plaster by chipping out chunks of the plaster. I like to start in the middle of the area and work outwards. to cut the lath I use a dremel or spiral saw (like a rotozip with a wood cutting bit). You could also use one of those oscilating tools. DONT use a recip saw, you'll tear **** up.
Take a look at wear the framing is located cuz you'll probably want to use it to patch back up the hole. This could be done with drywall and a decent skim coat of join compound to bring the surface flush, or you could put new lath up and replaster....if you're handy like that.
Also getting one of those handles that you can mount a reciprocating saw blades on to make a manual key hole saw is a brilliant $4 investment for this kind of job. So you don't shake loose the whole wall.
Besides patching squares of drywall and skimming the whole thing, there is also this stuff.
USG STRUCTO-LITE Basecoat Plaster by USG Corporation
You can tack in a little bit of chicken wire as "lathe" and mix this up as the "brown coat" or plaster under coat. It mixes kind of lumpy like oatmeal but has more fibrous staying power than joint compound so make sure you keep it below the level of the finished surface.
is asbestos or lead paint a concern?
If its old enough to be lathe there is often no insulation. Lead paint is an equal issue to any surface predating say the mid 1980's, plaster or drywall. It generally sticks to damaged plaster just fine. The chipping around wood work, windows is the bigger concern.
Originally Posted by qweezyq
House was built in 1908. I am sure there is lead paint on the ceiling.
Originally Posted by qweezyq
Is asbestos in plaster common? The ceiling in question does not look original. Our first floor ceilings are much smoother than the second floor. We think the first floor was replastered at some point (unknown date). Ceilings are definitely plaster and not drywall.
Since it is the ceiling between the first and second floors I doubt there is any insulation.
The asbestos to worry about for that age will be off-white whispy stuff loosely around water pipes and stove pipes. Looks almost like medical gauze. If they added fiber to the plaster it was likely literally horse hair.
Or if someone in the 60's or early 70's put down asbestos lineoleum-style floor tiles.
Prob. not lead paint on ceiling. Lead paint was usually used on wood trim, not waslls and ceilings. Invest $20 in a swab test kit at Home Depot. As for cutting the plaster and lathe, you don't want to cut deep because you rick not just the joists (less rick because you will feel the added resistance) but also cutting elec.lines. Get a Dremel Multimaster vibrating saw from Home Depot for $99 and put the semi-circular wood and drywall blade on it. You might need two blades and they are expensive, but they are the best thing for this job. They are very fine and won't shake the whole ceiling loose. If you do use a Sawzall type recip. sqaw, fit it with a fine toothed blade meant for cutting metal. You don't want big teeth that will grab the lathe strips and shake down all the plaster.
Originally Posted by stonefly
Hello and happy Tuesday,
When cuttng the lathe with a power tool such as a *** saw use a metal blade, the more teeth the blade has the better, less vibration/damage to the lathe that can break the keys in plaster ceiling in other areas that will cause the ceiling to sag. Otherwise use a sharp blade in a razor knife and wood chisel for such a small hole if you do not have a *** saw.
Last edited by HomeInspectorBC; 05-22-2012 at 10:27 PM.
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You can outline the opening with scrap wood to secure in place what you don't want to get loose. That's what we do.
Originally Posted by HomeInspectorBC
Thanks for all of the advice. You guys gave some great tips.
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