# Cutting a hole in 100 year old horsehair plaster



## GZ

As the title says...

I am getting ready to install a whole house fan in the upstairs hallway/attic. The job is a relatively simple one, except for the plaster problem.

The house has it's original horsehair plaster ceiling and walls. I need to cut an approximately 24" square opening in the ceiling without damaging the surrounding plaster.

I have, in the past, used a drill and kehole saw for small openings in walls (i.e. outlets). For larger jobs, where I needed to open up a section, I have had success with using a circular saw... But that stuff is heck on the blades!!!

The problem is... I know how easy it is to break the tongues off of the plaster that hold it to the lathe... The last thing I need right now is a sagging plaster ceiling... Eventually the hallway will be redone and the plaster will be replaced with fire-code drywall... but that is for another time... 

I am thinking of using my cordless circular saw and a cheap blade to cut the square in the plaster and lathe... But I am open to suggestions!!!!

Edit:

I may be picking up a diamond blade to do some concrete cutting... Would it be a good idea to use that on the plaster/lathe?


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## Basementgeek

I would put 1x2's up where the wood trim is going to be and use a saws all.
Less dust I would think. Secure the temp wood frame with drywall screws.

BG


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## GZ

Thanks for the suggestion BG... I have already discounted the sawsall for 2 reasons... One is that I have to cut around at least one joist and the other is because it is guaranteed to break the toungues, even with the wood frame. 

I have used my sawsall in the past to cut openings in plaster... It always ends badly!


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## Wrench97

I hate old shrunken wooden lath:grin:

The wood trim around the opening is a good idea, but instead of a sawsall use a circular saw with plywood blade, adjust the depth to just cut through the lath, cut the sides first, then lessen the depth of cut a hair cut across the joist, just make sure the end cuts fall into the space in the lath(where the keys are) that way you have the lath cut loose from the rest of the ceiling.


Edit I forgot be happy it's horse hair, after they ran low on horses they thought asbestos was a good idea..................................:facepalm:


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## GZ

I have no idea why I couldn't think of the word "keys"! I know that is what they are, but it was slipping my mind!!!! Thanks!!!

I am pretty darned sure this is the original plaster (house was built in 1910)... The walls I tore down in the back room were horsehair, so I hope that there were no major, mid-century repairs on the second floor!!!!! Asbestos is bad, M'kay... :lol:

That was my original plan... But I remember cutting out chunks from the back room... The blade is not very happy.... That is why I asked about the diamond blade... I have to buy a new grinder, since my buddy set my old one on fire and am planning on picking up a couple of 4.5 inch diamond blades to do some concrete work in the basement. It would be easier to handle over my head on a ladder! (9ft ceilings). 

Either way, the circular saw is probably the best bet... My cordless is relatively light and small but I am afraid it won't have the oompf to tackle plaster. My corded saw is quite bulky and heavy.


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## Wrench97

Sometimes installing the blade backwards to get through the plaster helps, then turn the blade around and cut the lath, also a carbide tip blade helps too.


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## Snobnd

I have worked in remolding most of my life, and I find the best way not to crack the plaster, is to use a drumel multi master $90 at home depot. :thumb:


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## GZ

I want to get me one of those... But I don't have the cash for it yet!


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## Basementgeek

Harbor Freight has a knock off of the Dremel for $40.00

Oscillating Multifunction Power Tool w/ Variable Speed

BG


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## SABL

Why make two messes and do the job twice?? Salvege the plaster only to replace it later?? Just plan on one big messy job and tear the old ceiling out....locate the fan where it is needed and do a proper framing job while you have access to the whole ceiling. 

Circular saw not a good idea.....that's one tool I do not like to invert for use....and the dust falls back into saw and can cause the guard to hang up. Sawzall not a great idea, either. Reciprocating blades are brutal on old plaster. Diamond blade is out.....unless you want to run the risk of producing live embers and set the house on fire. Diamond blades are not meant to cut wood.....dry oak lath is still tough and will smolder almost immediately from the friction of a diamond blade. 

The Dremel will be the best bet with the lateral reciprocating blade.....make sure you buy plenty of extra blades......:grin: Those have been around for 50yrs.....I remember having a cast cut off when I was a child and was amazed at how the cast was cut without cutting me. 

Or, you can make one big mess and get it over with.......three sheets of 5/8" FCX, a roll of DW tape, and a bucket of *+3 (or similar DW compound) will cost less than a new tool. And, the job will be done.

*You can use 'all purpose' but that stuff is hard to sand......and it shrinks.


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## GZ

I would love to make a job of it... But I am currently preparing to tear the bathroom and spare bedroom out for a much needed remodel!

My money will be tied up in new fixtures, FCX, greenboad, tiles, etc for that job! Before I start any major projects that needs to be done! 

The hallway is in really nice shape... No plaster buckling, cracks or otherwise. I just want to get the fan mounted before I start the bathroom job... 

I was only planning on using the diamond blade to cut the plaster itself... I know what friction blades can do to old wood!!!! :grin:

Perhaps I will buy one of those reciprocating multi tools... I am going to need it to do the cedar siding later on this year... 1/4" of caked on paint... lead... ooh... tons of fun...


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## SABL

Green board?? Sure you don't want to use Durock for any tub/shower areas?? The green board is easier to work with, but.........cement board will not break down. Green board is water resistant......not waterproof. 

What money?? How big is the hallway?? You're only talking 3 sheets of DW and a little paint. You will already have purchased DW compound and tape for the bathroom and spare bedroom.....throw a few sheets of 5/8" FCX on the shopping list.....:grin: But, if the ceiling is in that good of shape you may never have to replace it.

While you have the walls uncovered, throw in some fire-blocking where the original "balloon frame" studs go from foundation to roof. That should be the outside walls......unless the house is true brick.


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## GZ

I have no experience with cement board, unfortunately and I need to be able to finish the bathroom in a weekend... It's the only one I have!

It is a pretty major project... all electrical and plumbing will be replaced with the exception of the main drain. I am still debating the use of copper, PCB, or Shark-Bite for the water lines... 

My biggest issue with that project is sourcing the proper width insulation... Old construction... The studs are 18" on center, rough-cut... Makes it a PITA to find rolled batted insulation... I may go with 2" foam board ob the outside wall and blown insulation on the inside wall rather than have the headache. Add the vapor barrier and 3/4" fire-code sheetrock and I should be in better shape than the uninsulated plaster walls.

The hallway plaster is in excellent shape, as you can see in the attached pic. I am in no rush to tear it out. Actually, most of the walls and ceilings in the house are decent, with a few exceptions... The only reason I am tearing them out of the bedrooms is that I need access to the framework for re-wiring... Need to get this house updated and remove all of the oilcloth insulated knob and tube before there is a fire... If you saw what the previouse owners considered a house re-wiring, you would have a heart attack! There is only one place in the house where the knob and tube is properly connected to romex (through a ceramic insulated electrical box) and that is in the open framework of the attic... Where the inspector would see it...


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