On Apr 9, 12:14 pm, "BETAC-T" wrote:
I have an old house with wood lath and plaster walls, and I need to cut out
a lot holes in the walls for light switches, electrical outlet receptacles,
etc.

Here is what I am doing now, and here is what the problem is:

I am just cutting them out by hand, one-by-one, using hand-held wallboard
saws, etc. The problem is that it is hard to keep the underlying wood lath
from vibrating and causing a wider area of plaster to crack and break out.
I have tried making sure each hole is adjacent to one of the studs so at
least one side of the hole has wood lath that is nailed down to the adjacent
stud. And, I have tried being very careful, cutting out a little, reaching
in to hold the rest of the wood lath stable, and then carefully cutting the
wood lath. But it is still a mess, doesn't work very well, and takes a long
time for each hole.

I don't think using any kind of powered reciprocating saw or saws-all would
help and probably would only make the lath vibrate more and damage a wider
area of plaster than using the by-hand method.

The problem seems to be the reciprocating action of the saws, so I keep
thinking there ought to be some kind of small circular saw that could be
used and plunged into the wall to cut the lath without vibrating it back and
forth. But I don't have, and haven't seen, a circular-type saw that would
be small enough to do this.

I have thought about buying one of those drill bits that supposedly can saw
sideways to cut holes in walls (which I saw on TV), but I haven't found
anything like that in any stores and I have a hunch they don't work anyway
(which is probably why they are only on TV).

So what the heck do professional electricians do? I keep thinking they must
have a tool or know of a trick to make this easy, especially since they
don't want to damage their customers' walls when putting in new outlets,
etc.

Any ideas? Thanks.

I remember the first time I had a project that involved cutting into
the plaster walls. As I had a fairly large area to remove I thought a
circular saw was the way to go. I was really surprised when I touched
the saw to the plaster and it generated a rooster tail of sparks!
Didn't cut it very well either. That plaster is quite cement-like (at
least mine is). Since then I have used a sabre saw or a reciprocating
saw a few times, but as you say it is problematic in terms of
cracking, knocking the lath around, etc. It is also likely to break
off the "keys" that hold the plaster to the lath, leading to problems
later as the plaster gradually develops waves or bulges. Also, after
a few minutes the teeth on the saw blade are not just dull, they're
gone. You could try a rotozip. Bit life might be an issue if your
plaster is like mine.

When I need to cut the plaster now I use a a low-tech method: carbide
scribing tool (normally used for scoring cement board for tile
backing.) The scribing tool can be found in the tile section of a big-
box store for about $10. You just drag it along the line you want to
cut, a few passes will score all the way through the plaster. You
could probably then just pull out the piece of plaster you want to
remove and then cut the lath with a rotozip.

-- H