# Cutting holes in plaster ceiling. Safest way?



## cj133 (May 16, 2011)

Hi all,

I need to install some ductwork which will require a few 10x10" and 12x12" openings in my plaster ceilings. The largest will be 14x30".

I want to be as gentle to them as I can and am not sure of the best way to go about it.

I also need to be as clean as I can as the rooms are occupied.

I'm thinking an angle grinder with cutoff wheel and a dust collection shroud but want opinions as I would need to buy a dust collection setup.

Another idea was a rotozip with dust collector, but I've never used one and would need to buy it.

All thoughts welcome.


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## joecaption (Nov 30, 2011)

Good luck with trying to keep it clean, Roto Zip with a tile bit and a vacuum attachment or an oscilating saw with a tile blade and a shop vac would be your best bets.


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## jeffmattero76 (Jan 4, 2016)

I would suggest adding screws around the perimeter of your opening on the plaster you plan to keep, before you cut the holes. That will help prevent it from cracking or vibrating loose as you cut the holes. Is you plaster wood lath or gypsum lath? 

I have done this a few times for smaller holes, and i used a sawzall to make the cuts after drilling 1"holes at each corner. If you go this route be sure to get extra blades since cutting plaster dulls them quickly.

Sent from my LG-D415 using Tapatalk


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## Sir MixAlot (Apr 4, 2008)

Reciprocating saw or a SawzAll. You can catch a lot of the dust by holding a shop vac right by it while you're cutting. :thumbsup:

Make one of these dust containment bubbles with masking tape and .31 mil plastic to do your plaster cutting in the occupied home. :yes:


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## abrowning (Jun 2, 2008)

If this is really plaster and not Sheetrock I would go for the sawzall over the rotozip or angle grinder. The wheel cutter is easy to control but the high rpm and cutting surface creates dust particles so fine they will float for half an hour and coat everything. A toothed saw will create coarser dust that drops right to the floor. 

A mess either way but a cutting wheel is much worse.


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## MrElectricianTV (Nov 13, 2014)

cj133 said:


> Hi all,
> 
> I need to install some ductwork which will require a few 10x10" and 12x12" openings in my plaster ceilings. The largest will be 14x30".
> 
> ...


An angle grinder will blow dust everywhere and will be difficult to get precise cuts. A Rotozip would work okay, but may get jammed up with falling dust from the ceiling (Happened to me). I would use an oscillating multi-function tool. I have been using mine for drywall cutouts ever since I bought it. It cuts clean and does not blow dust everywhere. You may go through several blades.

This is the one that I use: http://tinyurl.com/AmazonMulti

I also have a much cheaper model from Harbor Freight which works very well, however it is a little on the heavy side to work with one hand continuously.


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## cj133 (May 16, 2011)

Thank you all for the replies.

This is wood lath and "horsehair plaster" to be specific. I think it's also called lime plaster, but I'm not sure. What I've always noticed is it doesn't seem terribly hard, but it's very sandy. I don't know if this is just because a lot of the plaster is 150 years old, or if it's because the guy was cheap and used too much sand. :biggrin2:

Right now, I think my plan is to frame the opening in the attic and glue the lath to that new framing. After a week I'll go back and cut the opening from the attic using a Sawzall and a metal fine tooth blade. I'll likely also temporarily frame the opening on the finished side with some 1x3's to sandwich the plaster against the lath for good measure.

I'm thinking this is just one of those things where a little extra prep will really pay off.

Luckily, I only need to do a few holes in plaster alone. The rest of them are in drywall over plaster, so not as critical.


One of these ceilings I spent a lot of time redoing and it came out very good. Good enough I decided to use satin finish paint on it. This is the one I really don't want to mess up on. I know a lot of people don't like satin on a ceiling, but I do, especially when showing off my plaster skills. :thumbsup:


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## abrowning (Jun 2, 2008)

My first house was a 1910 era farm house with horsehair plaster. As you say, it's sandy and has hair tufts in it. 

What I found was that cutting through the lath causes it to vibrate enough to break the keys off the plaster. Then the plaster loses its grip on the lath and big pieces just fall off. Sometimes if the blade binds in the cut it is enough to yank the lath off the stud which causes even more plaster to fall. 

The solution is to locate the studs surrounding the opening that you want to cut and screw temporary 1x3 braces to clamp down on the laths to prevent them from moving and breaking off the plaster keys. If you are cutting horizontally stay between the lath. 

Always cut with a fine blade. Then when you fill the hole attach cleats to the studs to mount your sheetrock. 

I always hated that sour taste in my mouth from the dust in that plaster.


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## abrowning (Jun 2, 2008)

cj133 said:


> Thank you all for the replies.
> 
> 
> 
> ...




Exactly right approach. I never tried the glue, but it couldn't hurt.


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