truth about asbestos in plaster.
plaster made before 1981 contains
use of asbestos dates back for
centuries,United States Gypsum, the largest
manufacturer of plaster, did not use asbestos
in it's materials until the 1920's.
The before 1981
rule may refer to lead paint, but not
asbestos in plaster.
most hazardous use of asbestos in plaster was
the use of asbestos fibers in acoustic plaster
that was used widely in the 1950's.
The main use of
acoustic plaster was in churches and
plaster was a lightweight, soft plaster for
ceilings that was mainly used for noise
reduction in areas where people converged, for
example church narthexes and hallways in
Acoustic plaster is easily identified by a
rough random texture. Usually an acoustic
plaster ceiling under 9 feet high has holes
poked in it from kids jumping up and hitting
the ceiling. This plaster was put on metal
lath, usually suspended, and didn't receive
any finish coat. It was intentionally very
|Sound attenuation is
used to soften noise and echos
in offices, for example, and areas
where people congregate such as church
narthexes, hallways in schools, etc.
This is the reason for acoustic tile,
and lightweight and soft acoustic
|Sound proof is the
other extreme. It is used to reflect
sound. This is preferred in concert
halls, church sanctuaries,
auditoriums, recording studios, etc.
Acoustic plaster should not
be confused with spray acoustic finishes, like
you see on motel ceilings, for example. These
finishes are a drying type material like
drywall compound with plastic or perlite
aggregate. The truth is, these materials are
referred to as acoustic, but have no sound
attenuating properties at all. (Another
myth). Spray on acoustic textures,
sometimes called popcorn, are probably called
acoustic due to the similarity in appearance
to acoustic plaster.
The main use of asbestos in
USG's product line was pipe insulation, boiler
jackets, early acoustic tiles for ceilings,
and roofing materials.
USG also manufactured
cement shingles, fireproof plaster (for column
and metal deck fireproofing) and acoustic
plaster. It is unclear how much, if any,
asbestos was used in conventional
The largest use of
asbestos fibers in plaster was for
fireproofing, that is for fireproofing metal
in commercial builds, and for acoustic
Before the 1920's, most
basecoat plaster in residential use was lime
and sand, and not gypsum plaster. It is
doubtful that a horse and wagon plasterer
would go out of his way to find manufactured
asbestos fibers to put in lime plaster.
The reinforcing fibers in
lime and sand basecoat plaster was animal
hair. Another myth is that this animal
hair is horse hair. Even though plaster
sometimes contained hair from horses and even
humans, most of this hair was from cows and
pigs, or animals shaved for leather making.
Farmers usually saved up their hair from
butchered animals and traded it at the farmers
market, where it was sold for plastering use.
Why do I refer to basecoat plaster and not the
finish coat plaster ?
finish coat for plaster was made usually from
lime and gauging plaster,
or lime and moulding plaster. Fibers in the
finish coat would show, so weren't used in the
Acoustic plaster was just the basecoat left
with no finish coat.