Cutting into Plaster all for electrical box

[Bill Davis Jr]

Just purchased a 80 year old house. It is a Ranch style house with wood lathe and plaster. No chicken wire.

What is the best way to cut into the plaster and lathe to add additional electrical boxes? I have seen were you could use a grider and a diamond blade. I tried this and it seemed as if it was burning the lathe.

Is the Dremmel the only way to go?

Thanks,

Bill

[Colbyt]

Your grinder and a diamond blade are fine for cutting the plaster if you can live with the dust.

A dremel or rotozip with a wood cutting bit will do a better job on the lathe after the plaster is removed from the area you are about to cut. A jig saw works but will shake the lathe more and might create some problems if the lathe is loose or in those spots where there is only one nail holding the remaining board.

A low tech almost dustless way to cut the plaster is to mark the box outline and use an old smaller screwdriver to score the line and then chip out the plaster. Only the first 1/8" or so is the "hardcoat" the rest is pretty soft stuff.

Just another side note; if you are drilling up from a basement or crawl into the wall cavity use a wood bit for the first 2-2 1/4" and then switch to a masonry bit because there is almost always 1-3" of mortar drippings inside the wall cavity that will ruin a wood bit real fast.

Have fun. I recall those days.

Colbyt

[Phisherman]

I know you have wood lathe and plaster, but a drywall saw should work great, and produce a lot less mess than a power tool. These saws are inexpensive, but pick one that fits well in your hand. Be careful about hidden wires or pipes in the wall.

[Clark Griswold]

Put the outlet next to a stud and make your first cut farthest away from the stud. Obviously your last cut will be the one that butts with the stud. I drill out the four corners and use a jigsaw.

If you make your cuts the opposite way you run the risk of wrecking your wall as the lathe will shake in the wall. Mud and a large cover will fix it.

[Wayne Whitney]

I believe it is best to do this job in two steps, first the plaster and then the wood lathe. For the plaster, it sounds like the diamond blade and grinder would work well, assuming you can control the depth to avoid (most of) the wood lathe. I use a rotozip tool with a "ceramic tile" bit and set the depth appropriately.

For the wood lathe, do not use anything with a reciprocating action, as it will likely shake the adjoining lathe free of the plaster. I use a rotozip tool with a wood cutting bit.

Cheers, Wayne

[scott_z500]

It's OK to drill a hole then use a jigsaw with a fine tooth (metal cutting) blade on a low speed setting.

[Steve Manes]

If you want plaster dust in your corn flakes downstairs.

Clark Griswold's method is the same as mine. Drill all four corners and use a drywall saw, starting first with the horizontal cuts, then at the side furthest from the stud. If the box is centered between studs, saw a little one side then a little on the other side to minimize breaking the key between the lathe and the plaster. For the same reason, don't use a jig saw.

I've tried Dremels, I've tried Rotozips. Spiral bits don't work well on old plaster lathe.

Steve Manes Brooklyn, NY

[The Real Tom]

Have a shop vac (outside the window is the best) and suck up the dust as it's generated.

hth,

tom @

[nobody]

I drill all four corners with about a 1/2 inch bit. Score a line around the perimeter of the box with a utility knife. Then use a sawzall, with a 6" blade, fairly coarse. The key is high speed, but low pressure on the blade. Otherwise, the lath will be shaken loose. After opening up a hole, I can reach in and hold the next lath. Also, cut the side closest to the stud last, if possible. Different houses, with different plaster, will cut differently, of course, but this method works for me.

[Steve Manes]

Whatever works. My friend uses a Sawzall too but drives a few drywall screws into the lathe an either side of the cuts. That way they won't flap around. But it's so easy to do with a drywall saw that it's hardly worth the effort of lugging the Sawzall up from the shop.

Steve Manes Brooklyn, NY

[... ...]

Geez...... Why does everyone in here like taking the long road??? You only need to drill two holes at opposite diagonal corners and you can use a dry wall saw but be warned plaster will dull a dry wall saw quickly. We used to use key hole saws with replacable blades .

Bill