opening(s) in plaster ceiling

[rokosz]

I'm replacing 2 aged smokes in a hallway. A year or two ago I replaced a fixture and added a second in the same hallway ceiling . I got 'em eventually but still didn't like how I got there.
The old smokes are lo-v -- they're stick-ups with just a lo-v wire penetrating the plaster.

Replacements will be 15-amp circuit interconnected with 14/3 wire.

Last time i tried using a sawzall to cut the lathe to the opening dia. of the box -- that shook and cracked alot of plaster I'd hoped to keep. So, I cut the lathe back to o.c. stud either side, installed bracket, box, wire and fixture, drywall etc.

In general, anybody got a better method? At that time I used a Dremel attachment (abrasive?) wheel to put a clean edge on the cut lathe. I remember the wood smelling of burning. I also bought some sort of proper (metal) dremel wood cutting wheel -- but realized I didn't have the proper attachment for that wheel, and that missing part was somewhat pricey or just not right for my model of Dremel, so put it aside. I muddled through but would prefer to not create even more work than I envision.

Since I've got two separate identical efforts-- I'll spring for the pricey part/tool barring any other ideas. I recently learned small sawzalls are made (compared to the whole house demolisher I have).

pros or cons besides price?

thanks

 

[Snoonyb]

Wood lath is always a hassle and since I learned to do this before the variety of starett bits became available, we just bit the bullet and did the patch.

 

[bud16415]

Not exactly what you are doing but similar and I have done my share of shaking lath and hearing what sounds like a hail storm inside a wall as the plaster keys break off and fall down the wall.


I rewired a whole house and this is what I did.


I made up pieces of half inch plywood about 2 inches larger than whatever box I wanted to install. I cut an opening in them to just fit whatever box I wanted to install and attached the box to the plywood filler. All that was done in the shop before I ever touched a wall. Then when I found my locations I took a knife and screwdriver, ice pick or what ever it took to chip away at the horse hair plaster without shaking the wall or breaking the lath I made the hole in the plaster about an inch larger than the plywood. I then marked the lath just a little larger than the box and cut it cross grain with a hacksaw blade holding the lath with channel locks or by hand and then snapping out the piece of lath with the grain. I then ran my wires and pulled them out the hole where the lath was cut brought them into the Jbox and clamped them and then fit the box and plywood adapter into the hole. I then drywall screwed the plywood to the lath at everyplace there was a loose end of lath and a few where the lath was notched. Now everything was solid again and the plywood set down slightly below the plaster about 1/8 inch. I used mesh tape half on the plaster and half on the plywood all around the repaired area and then I filled it all in flush to the box with drywall mud. It will shrink and crack by the next day or you could use patching plaster and avoid the cracking. I gave a few more coats and sanded it all out flush just barely covering the tape and feathering it out.


It was a lot of messing around but in the long run saved time not messing up the 100 year old plaster job. I had the plywood plates and boxes made up ahead of time and the old guy I was working with said where do you buy those things saying he could have used them a 100 times.

 

[rokosz]

bud16415, that is quite the solution.
I thought I tried a hacksaw -- but i hadn't removed all the plaster first -- so nothing to hold on to. <wiggle, wiggle>. Even in your scenario -- how;d you get the _first_ cut going on either side? the gap was too small for my blade -- probably about the time I broke out the sawzall. Now, ajigsaw blade would fit if you could keep it taut.

Other question -- how exactly did you attach the box to the plywood? Can't go through the bottom of the box, the box sits in the hole yes?

Short of a solution to the attachment, I'm gonna think through the plywood -- without the box attached and let it hang from the trad bracket.

btw, I'm not quite sure the plaster is a minimum of 1/2" either -- ahh but at least I can check where my foot came through from the attic side.

 

[bud16415]

bud16415, that is quite the solution.
I thought I tried a hacksaw -- but i hadn't removed all the plaster first -- so nothing to hold on to. <wiggle, wiggle>. Even in your scenario -- how;d you get the _first_ cut going on either side? the gap was too small for my blade -- probably about the time I broke out the sawzall. Now, ajigsaw blade would fit if you could keep it taut.

Other question -- how exactly did you attach the box to the plywood? Can't go through the bottom of the box, the box sits in the hole yes?

Short of a solution to the attachment, I'm gonna think through the plywood -- without the box attached and let it hang from the trad bracket.

btw, I'm not quite sure the plaster is a minimum of 1/2" either -- ahh but at least I can check where my foot came through from the attic side.

If your plaster layer is thinner use 3/8 or thinner material. I used steel boxes with the wire clamp inside. I found some that have a face clip at both ends they are adjustable so the face of the box comes flush in the end. I just screwed the box to the plywood with short screws.


Most laths are spaced about half an inch or so apart lots of room to get any kind of fine tooth blade in there.

 

[Sparky617]

For a round box, a hole saw on a drill would probably work better than a saber saw or a sawz-all. A hole saw doesn't reciprocate so it won't vibrate the lathe as much as a sawz-all.

 

[bud16415]

For a round box, a hole saw on a drill would probably work better than a saber saw or a sawz-all. A hole saw doesn't reciprocate so it won't vibrate the lathe as much as a sawz-all.

Most of the time the vibration isn’t in the saw it is in the lath being able to move back and forth with the blade. Its like trying to cut off a paint stir stick while holding it by hand on one end cutting the other. You should be able to buzz right thru but all it does is shake. The hole saw is a great idea as it makes the force in the thicker direction of the stick and the force always in the same direction. Plus if you have one large enough for an old work round box on the ceiling it’s a one step deal.


Wall outlets being rectangles is a little tougher problem. Plus a ceiling box doesn’t see the wear and tear a switch or outlet sees.