My 1920’s walls are all lath and plaster with the original heavy texturing. I am going to install some new electrical boxes and want too minimize the damage to the walls as matching the original texturing will be difficult. How do oI do it and minimize damage to the plaster? I’m thinking a spiral bit on my laminate trimmer.
Do I need to worry about supporting the lath once i cut an opening for the box and it is free fromthe stud?
Thanks
jw
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Replies
JW
I run into this problem alot in some of my apartments i've remodeled and here is the method I used with good results.
Instead of cutting both plaster and lath at once I first cut the plaster using a rotozip with a tile cutting bit (1/8 inch). Take it slow and steady. Applying to much pressure will snap the bit and they aren't cheap. Be most carefull at the end of the cut because if the rotozip vibrates the bit will definitely snap. They do sell a 1/4 inch tile cutting bit but i've never used it for cutting plaster. Should be sturdier but would put off a lot more dust.
Once you have cut through the plaster it will either fall out or can be broken into pieces and pried out. To cut the wood lath I switch to a spiral cutting rotozip bit (one designed for cutting wood).
One other note. I normally try to position my boxes so I cut totally through two pieces of lath and partially through two others. (instead of completely cutting 3 pieces of lath off). This gives you something to attach your box to and minimizes the comprimised lath.
Hope this helps! It takes a little getting used to and may take a little longer to do but if your goal is to minimize damage to your old plaster walls it works.
Dan
P.S. I use old work boxes so the hole I cut is only as large as the box. No plaster to repair.
I use a rotozip tool and bit like pghdan advocated. I simultaneously hold a shop vac nozzle in my other hand, turn both machines on at once and run them together. Little noizy, but absolutely no dust. My shop vac has a paper liner inside it to keep dust from blowing out of the tank.
I set my depth on my zip tool to cut thru the plaster only. Then I either change bits ( to a wood cutting bit) and proceed with rotozip...but sometimes I just cut lath with small keyhole saw.
I don't worry about attaching boxes to lath...I use "old work" boxes in these instances...the type with the ears...they work similar to a toggle bolt...holds in place very nice.
Davo
i've had goog luck with a4.5" grinder with a masonary grinder works really well but makes lots of dust. i have had someone hold a wet/dry vac hose close and capture most of the dust.larry
hand me the chainsaw, i need to trim the casing just a hair.
I was going to also suggest the vac, if the cutting tool doesnt have a shroud, think of a way you can fashion one. Save a ton of clean up. I talked with a guy that worked for an environmental management firm, and they would commonly do this rather than closing off total rooms. Things as simple as some foam pipe insulation and a funnel can make a dry shroud, also working in shaving cream or other liquid foam product arrests the dust.
Another thought you may try to add, Im not sure if it would work, is to masking tape off the area to cut to try to keep excess breakage down.
-zen
Edited 1/16/2005 5:42 pm ET by zendo
4.5" grinder is an excellent idea. I have done it a number of times with a diamond blade in it.
The thinner kerf of the diamond blade---(-compared to an abrasive masonry blade ) cuts down on a lot of debris.
Spread a drop cloth under the work area---use a little thought in how you hold the grinder---and the cleanup will be minimal.
The debris from the grinder seems coarser and heavier than drywall dust---and doesn't seem to want to "float" as far as drywall dust
Stephen
Kinda low tech, but I've been successful cutting/scoring the plaster with a utility knife, and then the lath with a jigsaw with a fine blade.
plunge cut with a circular saw ...
first 4 times just thru the plaster ...
check the lath ...
then thru the lath ...
or ... do the lath with a small hand saw (I do the lath with a sawzaw ... don't recommend that to a first timer)
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA
"plunge cut with a circular saw ..."
Funny...
You can't be serious can you? He did say that he would like to minimize the damage.
Are you talking about a 7-1/4" saw?
If you doubted Jeff's ability with a circular saw, you don't know him.
He can cut the whole thing with four plunge cuts without a scratch to the surrounding plaster.
I am serious.
I use a 4 1/2" grinder with a very thin concrete wheel (DeWalt C46S-BF). You definitely will appreciate someone holding a vacuum to the grinder exhaust.
You'll probably score the lath. At that point, I use a an 1/8" drill bit to perforate the lath so it breaks without pulling away from the surrounding plaster. As insurance against future cracks you can smear some stiff mixed Durobond on the lath surrounding the hole.
The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.
- Fyodor Dostoyevski
Cutting outlets into 100 yr old plater/lath has essentially been my "night job" for the last month. I'm generally only working late at night and there are kids sleeping upstairs in the 2nd floor apt. So being quiet is a limiter on me. I've ended up having good success with the low tech combination of drill, utility knife, and a key hole saw.
First you need to be centered on the lath, and this is pretty important. So I figure out where I want the box and drill into the wall with a 1/2" bit. This bit quickly becomes too dull to even scratch wood so use an old bit if you have one. I run the bit up and down removing the plaster to find the top and bottom edge of the lath. From the center of the lath I trace my outlet box onto masking tape on the wall. With the utility knife I cut out the trace into the plaster. After a couple boxes the blade is impressively rounded off. I've developed quite a respect for the strength and WEIGHT of plaster. Then with a sharp 3/8" drill bit or so I drill near the edges of the lath. Then I put the keyhole saw between the lath and cut into the drilled hold and get it cleaned out to make the up and down cuts. Here I only cut on the outward pull, supporting the lath best I can with my other hand while struggling to not rip into a finger.
Then I put a sharp blade into the utility knife and connect the saw cuts across the top and bottom of the box. This is cutting with the lath grain and goes pretty well. Score it several times getting all the way to the saw cuts and then just crack it out.
This works pretty well, a bit of elbow grease perhaps, but its very quiet and clean.
The top and bottom lath strips are still solid, but the middle one is pretty loose. I locate the box in the middle between studs. This way there is only 6" of the middle lath that is hanging somewhat loose.
eric
Lately I've done a lot of this in drywall but it might work in plaster. I use my fein saw with an old round blade (the one with a flat side). It cuts drywall well and because it cuts with a very short reciprocating action it makes very little dust that tends to fall straight down.
Smile. It could be worse. You could be me working for you.
Is that the multi master I think they call it?
The 2-step rotozip method pghdan described works well. Just one additional suggestion.
Tape a paper bag to the wall just below the hole you're cutting. Then most of the stuff you cut out will fall right into it.
After trying most of the ways described above, I've settled on scoring the plaster with a utility knife, followed by cutting the lath with a keyhole saw. It makes the least mess and in my dainty hands works best for me. Some of the plaster may chip away near the hole but this can easily be filled later with plaster repair compound.
Also, when I am done cutting the hole, I stabilize the cut lath as follows. I clear the plaster from the back of the lath inside the hole. Then I cut two small pieces of lath about 2" longer than the sides of the hole. I apply construction adhesive to the strips, then maneuver them into the hole, apply them to the back of the lath, and secure them with small clamps. This little frame provides a strong base for attaching new work boxes to the wall.
A drywall hammer.
EZ.
diamond blade..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
I have done what pghdan does with hotcake's modifications to reinforce the 2 pieces of cut lath. It works great, and if you use construction adhesive, it is thick enough to hold the reinforcing lath strips in place without the clamps. I also try and attatch the box right next to a stud so the lath is only cut on one side, and I can screw through the side of the box into the stud for a very secure outlet. One last thing, I use plastic work boxes and if they wind up a bit proud of the wall surface, I just sand it flush with a touch of an angle grinder.
I have tried the circular saw, the sawzall and jigsaw. Each has at one point grabbed a piece of lath and nocked a hole in the wall much bigger that I wanted. Skip these if you want minimal damage and plaster to patch, especially if the plaster is a bit loose ) isn't all lath plaster loose?).
yea from reading all the responsses your synthesis sounds right. I'm a bit afraid of any of the recipricatiing saws just vibrating too much. I"m temped to try one with a sheetrock knife but this is old hard plasterSomeone made a good point of using 1/8 inch instead of 1/4 bits to minimize dust.Course this means I'll proobably end up buyinig a new tool, sigh, Rotozip? Dremel Advantage, maybe a laminatee trimmer with 1/8" collet.I've seen the Freud ini a kit with a plunge base which might actually help
I used a rotozip, and do have one caution, however - inside those walls it is really dry and dusty. The rotozip bit can generate quite a bit of heat when it begins to dull (which it will do quickly). Be careful of sparks and embers from burning wood or from hitting a nail. I kept a squirt bottle at hand, shot a few squirts on the wood first, then shot some in the hole afterwards just to be sure. It helps keep some dust down a bit too.
You can pick up a rotozip on eBay cheap.
Also as the first post said, adjust each outlet opening height a bit so you only cut 2 laths all the way and 2 just partially; it will be a lot more secure. If you do not glue the little reinforcement piece in the back, the plaster may be intact now, but as soon as your son knocks against the wall next to the cut lath, you will see how flimsy old unsupported plaster is.
Good luck,
Portland
rotozip alos needs a blade change half way thru the job ...
the plaster bit can overheat thru the lath ....
I once ... at home .. was being lazy. Only had some drywall bits .. no plaster ...
so I zip thru the plaster ... not thinking ... start on the wood lath.
it's smoking ... think ... only a little to go ... don't care if I toast one zip bit ...
so I push on ... a little bit of saw dust falls into the wall ....
then ... a coupla good sized burning embers!
Luckily I was in the LR ... right at the kitchen door ... ran in and started dumping cups of water into the wall ... wife walks in ... looks confused ....
the whole time ... I'm thinking about my 100 year old studs and balloon framing with no fire blocking ...
Jeff Buck Construction
Artistry in Carpentry
Pgh, PA
I'm curious about screwing the box into a nearby stud.....I did this with some boxes because the surrounding DW was crumbling (Memo to self: never rely on DW to hold a box). However there wasn't enough room to run the screw sideways so I had to toenail them in (2" #8 deck screws). At some point the box started tilting inwards on the side next to the stud. I ended up with a good solid box but with one side inside the wall by about 1/8" and the other outside the wall by a similar amount. Hard to attach a face plate to it. What did I do wrong? I don't see how I could get even a 1-1/4" screw in sideways in a 1-gang or even 2-gang box, even though I have a right-angle attachment for my drill.
That is why I used the plastic boxes. they twist a bit when you put the screws at an angle, but I position them so they wind up with the high side just above the wall surface. After the outlet box is in, I fill in any space around it with setting joint compound or plaster. Then when dry I just touch the high parts with a sanding disc on my angle grinder and knock it down flush with the wall surface. This will all be hidden by the outlet cover, but it is still important to give you a solid surface, keep the plastic box from twisting and seal drafts. I use the edges of the wall face to pull the outlets flush with the wall, not the box. The outlet cover also helps. This works beautifully, and the outlets are rock solid, flush and straight. It looks like original equipment when you are done and you never have to worry about them wiggling loose later.
I have done a lot of these...
Portland
I can't use plastic because my old house has BX cables and needs metal boxes for grounding. I suppose I can try sanding down the side of the box, should be quite a fireworks display....
That could be quite a show! I did try doing this with a few metal boxes when I was figuring out a system. I used something like a small finishing nail taped to the edge of the metal box to act as a shim so the box pulled down square. This sort of worked, but not as consistently as my plastic box method. Good luck.
i started reading this stream to get insight on buying a rotozip instead of a jigsaw.
sounds like the rotozip bits are brittle and expensive. think i'll go with the jigsaw.
as to the electrical boxes in lath and plaster discussion, i have had good success with a series of 1/8" drill holes at 9 spots (corners and middles) of the elec box edges. gives the plaster something to crack to. then cut out the lath with a japanese keyhole saw like this:
http://www.leevalley.com/wood/page.aspx?c=1&p=32931&cat=1,42884
try to line the box up with a stud (or strapping on exterior walls), look for nails in baseboard below to find the studs/strapping.
I have also had excellent success holding the whole works together after the box is installed by blasting in some low-expanding foam. it seals the whole, insulates (if an exterior wall), somewhat 'glues' everything together, and you can always trim back the foam after it sets up. it also gives a sturdy backing to plaster up to if the plaster hole gets bigger than you want it to.
i love old houses
"I'm curious about screwing the box into a nearby stud.....I did this with some boxes because the surrounding DW was crumbling (Memo to self: never rely on DW to hold a box). However there wasn't enough room to run the screw sideways so I had to toenail them in (2" #8 deck screws). At some point the box started tilting inwards on the side next to the stud."
Most plastic boxes are tapered, so they will tip if you screw them to a stud. The flange on Bake-o-lite boxes can sometime be ground to get a flat side, or you can use metal. Unless it is a double box or larger though, it's not easy to use a stud.
I work with mostly very fragile plaster, so I have adopted a gentle method.
First, drill a few 1/8 pilot holes in the center of the proposed cutout to figure out where the lathe is. Ideally, you would completely cut one lathe, and partially cut the ones above and below. This gives your box better support. Once you find the edges of the 'center' lathe, adjust cutout area accordingly, and trace box onto wall.
Use utility knife to score cutout line until you get down to the wood, then gently chisel out plaster. Place drywall screw in center of center lathe. Pull on drywall screw to support lathe while drilling large pilot hole at one edge of center lathe.
With the teeth set to cut on pull stroke, use hacksaw blade (in holder handle) to gently cut lathe. I find hacksaw blade is the perfect tool because the teeth are finer than jab saws.
Once center lathe is cut, you can brace the edge lathes with your hand or a clamp while cutting those. Once hole is of proper size, you can soak all the raw edges with white glue to consolidate the plaster and prevent the hole from 'growing'. If the lathe came a bit loose in the process, inject white glue between plaster and lathe, and use quickclamps or spring clamps to secure while glue drys.
Once in place, I generally caulk around the box for additional support and airsealing.
any hints or suggestions on what kind of holesaw or like for providing 2" holes for 1 1/2" adapter on cellulose insulation blower
power by 1/2" drill motor
I do it a lot like you do. But to cut the plaster, I use a diamond blade hand grout saw. It cuts quicker and easier than a utility knife, and doesn't get dull, making it useless for other purposes.
I glue the plaster to the existing lath like you do, and also glue in vertical side reinforcing strips of lath in the same step.
-- J.S.