Need some help here. I’m rewiring a house that has plaster that is pretty weak. I wanted to use blue old work boxes and am finding that the screws which hold the flip up tabs that sandwich against the back of the wall are not long enough such that it puts the ears not back far enough to get behind the lath. The plaster is already pretty crumbly (moreso than usual for plaster). Cutting the holes alone is problematic, it’s keeps fracturing more. I then wanted to “bust” out some of the lath behind the plaster hoping to decrease the thickness that way so the old work boxes will work. For obvious reasons that exacerbated the problem.
When I busted out some of the lath the tabs would indeed grap like they’re supposed to, but even ever so lighlty tightening the tabs caused the front plaster ear on the box to pull thru the plaster. Now I have boxes that fall thru into the wall with no means of support now that the hole is oversized. I got one box to hold, but as I started doing the wiring connections, the stress from moving the wire inside the box and pushing the wires into the box caused the box to blow into the wall. Now the box won’t fit anymore for the same reason….broken plaster making the hole oversized. .
Help….!!!!!! Suggestions? What to do? I got 8 oversized holes now that won’t hold a box, that’s 8 hole patches I need to do. I have 10 more boxes to cut into the wall. What other techniques will work and save me a bunch more patching??
Replies
Willie, Im a carpenter not an electrician but I just had this conversation with one of my electricians. He uses the metal replacement boxes with old work metal straps that fold into the box. The staps are T shaped and hook in behind the lath at any depth. I don't know the exact name but I am sure you can find them. hope this helps
oooo, my mistake, those straps are called madison hangers, or battleships
I think what snapper is referring to is called a gemdandy ¯.....
Edited 1/3/2006 7:36 am by maddog3
actually the gem dandy¯ is still made by Garvin and is a CB-8, ..used cases of them in Chicago's bungalows, back in the 70s..always a bitch, tile on top of wire, on top of wood lath, AND fire blocking above the box or right where the box had to be .....
Your problem is the plaster, not the boxes.
There are deep boxes of the deign you are attempting to install.
Rotozip is the best way to cut through. I would likely try to fasten a piece of wood behind the plaster (screws through plaster and lathe) to one side of the opening and screw the box to it.
Tough nut that crumbly plaster. You may have to cut large holse and patch in.
Eric
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It's Never Too Late To Become What You Might Have Been
I've done over a hundred boxes through old plaster in my 1886 house, and tried ALL of the choices. Here is my exhaustively researched solution.
1) find a stud - locate box against either side. Use a blue plastic NEW WORK box with all the nail retaining clips cut off flush, leaving a clean rectangle. Drill two 3/16 holes in one side about 1" back from the front edge
2) find the lath locations
3) locate the box up and down so that the top and bottom BOTH fall within a lath strip
4) Cut an accurate hole through the plaster with a utility knife. NO known blade will cut both plaster and wood lathe - much plaster has enough sand in it to instantly dull anything, even TiN coated bits and blades.
5) Cut the lathe with a jigsaw. First cut the whole strips on the side AWAY from the stud. Next, cut these strips by the stud (the reverse order will vobrate and break the plaster). Next, notch the top and bottom lathe strips for the top and bottom clearance of the box.
6) slide the wires thru the BACK (not bottom) of the box
7) screw the box to the studs with 1-1/4" drywall screws, flush with the surface of the plaster
8) wire normally - the box will not move
THIS IS THE SOLUTION - don't listen to anyone else - really!
Forrest
Here's my technique, which is a slight variation of McDesign's approach -- only here, you don't need a stud. 1) Use an "old work" metal box (the kind with the back corners cut off at a 45 degree angle, where the wires enter the box), with madison clip others have described. 2) Use the box to draw an outline on the plaster. 3) break away enough plaster to find one full lath.4) Now redraw the outline of the box, so the box is positioned over the full lath, and half of the lath above and below. 5) Cut the whole lath . I like to use a sharp keyhole saw, since the vibration of a jig saw will too often either break the keys, or break away plaster you do not want to remove.6) Use the saw to cut (vertically) what you will need to remove from the top and bottom partial lath. 7) use a utility knife to score between the vertical cuts, then gently break off the pieces with a pliers (I use a lineman's pliers)8) Install the box, tighten the madison clip, then screw the ears into the lath with #4 pan head screws (1/2" long). Drill a pilot hole, so you don't split the lath. Slow, but effective. Actually, not so slow when you get the hang of it.********************************************************
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> 4) Cut an accurate hole through the plaster with a utility knife.
I find that a diamond blade hand grout saw works great for making precise cuts in plaster, ideal for small jobs like electric boxes.
Has anybody tried using a consolidant to firm up crumbly plaster? Given access to the back side, I've been able to stabilize it somewhat by squirting yellow glue between the lath. That helps a lot where the keys are broken, but not if the actual plaster is weak.
-- J.S.
I've used plaster washers beside the box to make sure the plaster keeps it's key. They sell them at lee valley and some hardware stores.
trick for cutting the hole in plaster/lath - as previously posted - mark the box, remove the plaster to expose the lath, cut the lath about 3/4 on one side, then cut the other side completely and break off the partial cut side - partial cut keeps the lath "fairly" stable so more of the plaster keys don't break off - partial lath removal as previously posted
The bendable straps mentioned work well.
Another angle might be to locate the boxes next to a stud, screwing through the side of most any box into the stud. Firm box, not relying on weak plaster to hold into position.
A great place for Information, Comraderie, and a sucker punch.
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Quittin' Time
I was thinking MAdison clips myself but then again if you plug a heavy duty plug in and pull it out it might pull the whole box out if the walls are that thin.
You have to find a stud to go up against and use a plastic box and screws.Thats the most solid choice IMO.
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let's review the problem.
OK.
Longer Screws!
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa