On Feb 9, 11:58*pm, Larry Jaques
wrote:
On Sat, 9 Feb 2013 20:50:16 -0800 (PST), Greg Guarino









wrote:
On Feb 9, 11:04*pm, Larry Jaques
wrote:
On Sat, 9 Feb 2013 06:57:10 -0800 (PST), Greg Guarino

wrote:
OK. Was 16" "standard" before there was sheetrock? (and yes, I'm aware
that even if it was, I might not find that spacing) The house was
built in 1939, I think. My house has plaster walls as well, but over
"plasterboard"; like sheetrock, but with a grid of holes for the
plaster to grab onto. Their house is just plaster on lath.

My 1939 California bungalow in Vista was built using full 2" x 3"
rough sawn cedar and redwood studs on 24" centers. It also had knob
and tube wiring which looked like a busy Union Telegraph Center in the
attic. 1/4" ply topped the studs for the walls and ceilings, and the
floor was full 1" thick by 4" (or 5"?) wide pineywood.

In demos, I've seen plaster over chicken wire, plaster over lath, and
plaster over chicken wire over lath, but all had studs behind them.
I think most were built 24" OC and built before WWII. *Lath is spaced
to provide a place for the plaster to overflow behind it and lock it
to the wood. *I haven't seen your holey lath before.

It was apparently called "rock lath" or "button board". Here's a
photo:

http://starcraftcustombuilders.com/i...terWall/Perfor...

Whoa! *Dat ain't lath like I know it. *They're long, thin strips.
Interesting. 18x36" strips? *It's downright weird.

I found this:

"Gypsum or rock lath is a pre-manufactured plaster board, generally 16
inches by 48 inches in size, and 3/8 inch thick. Rock lath became
popular in the 1930s as a less expensive alternative to wood lath. It
is nailed directly to the wall studs and receives two coats of plaster
over it. The rock lath is called the first coat and replaces the wood
lath and the brown coat of the previous wet plaster system. The
second coat is a cement plaster about 1/4 inch to 3/8 inch thick. The
finish coat is then applied, which is comprised of hard finish
plaster, and is approximately 1/8 inch thick."

Here's a photo of what this kind of wall looks like from the inside:

http://inspectapedia.com/interiors/P...th014-DJFs.jpg

In my house the first coat of plaster is darker, more grey, than it
looks in that picture. But the "fingers" of plaster protruding through
are very much like what is shown.

I can tell you from experience that that first coat of "cement
plaster" is some pretty rough stuff. I used a regular sheetrock Roto-
Zip bit to cut out around an electrical box (why, you ask?). It worked
well for the first two inches then stopped dead, like I'd hit an
object behind the wall. I pulled the bit out of the wall and inspected
it. A 1/4" or so of the bit had been worn down to a 1/16" thickness,
exactly where it had been in contact with the grey "cement plaster".

The positives and negatives are pretty much like what you can read
online. The walls feel nice and solid, much moreso than sheetrock. But
yes, cracks can sometimes develop. I haven't had too much problem with
that, but here and there I've had to make a repair.

So here's the "why" about cutting around the electrical box. I had a
location with two 3-way switches, one above the other. They were of
the old "despard" type, which uses a plaster ring that is unsuitable
for any current switch. So I had to cut out a piece of wall large
enough to remove the whole double-gang plate. But the fun was only
beginning. It turned out that the existing box had screw thread
locations that are also no longer standard (they were inset from the
corners of the box about an inch). And get this, the box was NOT
located against a stud. It had an arm that went off to one side
several inches which was then affixed to the nearest stud. So
replacing the whole box would have required much more damage and much
more repair. If the builders weren't already dead I might have had to
kill them.

I ended up tapping threads into the corners of the *rear* panel of the
box and using long screws to hold the new plaster ring on. Followed by
an education in how to repair a hole in a plaster wall. Another "2
hour job" that took a weekend.