Channel in old plaster lath

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JJWalecka

Senior Member
Location
New England
Cutting a six inch by twenty foot channel in old plaster and wooden lath.
What would you use to do that?

Score the plaster then scrap it out?

How time consuming is it to do that with a multitool?
I assuming it's going to make a God awful mess with the vibration.
 

JoeyD74

Senior Member
Location
Boston MA
Occupation
Electrical contractor
Cutting a six inch by twenty foot channel in old plaster and wooden lath.
What would you use to do that?

Score the plaster then scrap it out?

How time consuming is it to do that with a multitool?
I assuming it's going to make a God awful mess with the vibration.

Are you cutting along the lathe or across it? A diamond blade in a circular saw set to just cut the plaster then a fine plywood blade to cut the lathe.
I cut the plaster an inch or two wider than the lathe so it can be patched easier with thin blue board and plaster.
Its dusty no matter what you do so plastic off your area and use a shop vac on the saw.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
I would use an angle grinder.

In addition to cutting through the plaster and lathe, another important factor is straightness of cut. A straight cut is easier to repair with drywall. A circular saw is able to make much straighter cuts than an angle grinder. In fact, you could take two screws and fasten a 2x4 jig to the wall to get super straight cuts if you want.

Also you have much better depth control with a circular saw.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I would try to find a blade that will cut the plaster and lath at the same time. Otherwise, you risk breaking the "keys" of plaster that hold it to the lath.

I don't enjoy working with plaster. I hate finding metal lath even more.
 

growler

Senior Member
Location
Atlanta,GA
I would do whatever Larry suggest that way I would have someone to blame it on if I screw it up.

Actually I would probably just tell them to get whoever is going to be doing the patch work to cut the channel. :huh::lol:

Probably 200 years of lead based paint. Sounds like about 10 sq ft to be removed.
 

peter d

Senior Member
Location
New England
I'd use a grout blade on the multi tool, it will cut through old horsehair plaster like butter. Then I'd pull the lath out by hand.
 

chris1971

Senior Member
Location
Usa
Cutting a six inch by twenty foot channel in old plaster and wooden lath.
What would you use to do that?

Score the plaster then scrap it out?

How time consuming is it to do that with a multitool?
I assuming it's going to make a God awful mess with the vibration.

Multi tool or a grinder with a ceramic blade.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
One other thing to note in commercial buildings where some fire rating was desired very old plaster contains asbestos.
 

sw_ross

Senior Member
Location
NoDak
I'd use a grout blade on the multi tool, it will cut through old horsehair plaster like butter. Then I'd pull the lath out by hand.

I used the grout blade and oscillating tool to cut in some retro- can lights last week.
The job sucked! Those blades aren't cheap and I burned through 2 of them to cut-in 4 can lights!

I didn't anticipate that when I bid the job!
It took longer than anticipated and made a nasty mess of the living room!

Live and learn!
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
I used the grout blade and oscillating tool to cut in some retro- can lights last week.
The job sucked! Those blades aren't cheap and I burned through 2 of them to cut-in 4 can lights!

I didn't anticipate that when I bid the job!
It took longer than anticipated and made a nasty mess of the living room!

Live and learn!

Next time use a reciprocating saw with a cast iron cutting blade (or a masonry cutting blade if you can find one). Works well. Blade is thin enough to turn a tight radius.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I used the grout blade and oscillating tool to cut in some retro- can lights last week.
The job sucked! Those blades aren't cheap and I burned through 2 of them to cut-in 4 can lights!

I didn't anticipate that when I bid the job!
It took longer than anticipated and made a nasty mess of the living room!

Live and learn!


Uhh! Don't you know they make carbide grit hole saws for this? Long thread on it awhile back.

-Hal
 

jeff48356

Senior Member
I would do whatever Larry suggest that way I would have someone to blame it on if I screw it up.

Actually I would probably just tell them to get whoever is going to be doing the patch work to cut the channel. :huh::lol:

Probably 200 years of lead based paint. Sounds like about 10 sq ft to be removed.

That's what I would do too. In fact, I always ask my customers to use a carpenter or handyman to do tasks that are quite involved from a carpentry standpoint. I don't have the right tools anyway, and this is one of the reasons I don't. It is beyond the scope of what I do.
 

jeff48356

Senior Member
I used the grout blade and oscillating tool to cut in some retro- can lights last week.
The job sucked! Those blades aren't cheap and I burned through 2 of them to cut-in 4 can lights!

I didn't anticipate that when I bid the job!
It took longer than anticipated and made a nasty mess of the living room!

Live and learn!

Another thing.. if the house is old enough to have hard plaster with lath, then it's old enough to have ungrounded wiring throughout, possibly even cloth-covered or old BX. I would have passed on that job.
 

PaulMmn

Senior Member
Location
Union, KY, USA
Occupation
EIT - Engineer in Training, Lafayette College
6" x 20' is either one very tall ceiling, or you're going horizontally.

In either case, you want to minimize vibration to avoid destroying plaster keys. Then you'd have a job trying to re-anchor the plaster.

I like the idea of the guy who's going to patch the plaster is the guy to cut the channel.


New question-- what in the world is being installed? If you're going horizontally, are you going to have to notch the heck out of the studs??
 
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