zek wrote:
On May 28, 3:55 pm, "RogerT" wrote:
zek wrote:
my house has walls that are very thick and heavy.

I assume that you probably won't write back but .....,

What are the walls made of? Is it an old house? Are the walls made of
plaster over wooden lath? Are they made of some other type of masonry
product?

Some kind of double layer material maybe plaster. The inner layer is
very gritty like sand.

I was cutting cement and cinder block with a dry diamond blade. I know
all about dust.

Greg

Thanks. Sounds like they are plaster walls -- a thinner layer of white
finish plaster over top of a thicker layer of gray or light brown
sandy/gritty "rough coat" plaster.

Under that, attached to the rough coat plaster, should be either wood laths
or maybe a metal lath/mesh.

If it is wood lath underneath, the saw blades will last longer but it's a
real pain using a sawzall because the wood laths vibrate back and forth and
break up the plaster pretty far around the outlet hole you are trying to
create. If it is wood lath, my guess is that the plaster is destroying the
demo blades because they are mostly made to cut wood.

If you happen to have metal lath under the plaster, the metal will kill the
sawzall blades faster.

I have found that cutting outlet holes in lath and plaster walls is a real
challenge. If there is wood lath underneath, sometimes you can use the
angle grinder that someone suggested, or even one of those vibrating Dremel
tools, to cut just the plaster and break it out down to the wood lath. Then
use a small saw (even a hand saw for cutting drywall) to carefully cut off
the wood laths while holding each lath so it doesn't vibrate back and forth
while you cut it.