old plaster wall with no lath!!

[design house mtl]

while taking down an old plaster wall, i was surprised to find no lath beneath the plaster, but some kind of tar paper/plaster substrate. its roughly 1/4" in thickness and has about 4 layers of what seems to be tar paper with plaster between the layers.

has anyone come across this method and would there be asbestos in it?

the house is in montreal and was built around 1900.

thanks for the help!!

[homebild]

while taking down an old plaster wall, i was surprised to find no lath beneath the plaster, but some kind of tar paper/plaster substrate. its roughly 1/4" in thickness and has about 4 layers of what seems to be tar paper with plaster between the layers.

has anyone come across this method and would there be asbestos in it?

the house is in montreal and was built around 1900.

thanks for the help!!

Wood lath was the original backing for plaster in homes, but by the early 1900s, 'rock lath' type products began to appear.

These were typically 1/4" thick sheets that resembled today's Hardibacker boards or concrete backers used under ceramic tile.

These 'rock laths' were originally composed of cement based fillers and used extensively until they were replaced in the 50s with gypsum based 'rock lath' plaster backerboards.

To my knowledge these early 'rock lath' boards did not use asbestos.

Some did still use horse hair, however.

I've seen a good bit of the stuff when I worked in New England some years ago.

[Don_P]

If so I've heard one caution if you hit horse hair. It sometimes came from the tannery and apparently had arsenic and heavy metals in it. Pretty much if you don't know what you're in, assume it was better living through bad chemistry. 50 years of household chemicals saturating something is bound to be bad for a body.

I ran across a neat story some time ago in a book by David Lyle on masonry heaters. Back in old England at some point there was a decree that standardized the size of a brick. Another law later said that a fireplace back had to be at least 2 bricks wide. This resulted in 16" being a common firewood length. Peasants would often build the shell of their house and move in, finishing it off as time and money permitted. The easiest place to get lath was nice straight chunks of firewood and it was something to do on long winter nights. So we started spacing framing on 16" centers to accomodate the firewood lath. I've had an English engineer poo poo that, but it does sound plausible... and its a neat story.