Sprayed coatings of asbestos contaminated vermiculite
Description
A coating colloquially known as popcorn, due to its popcorn appearance, which contained the mineral raw material vermiculite mixed with gypsum plaster. Exfoliated vermiculite ore has natural fire retardant qualities and is still used industrially. Asbestos was not intentionally included in the spray-on coating.
Vermiculite can be naturally contaminated with asbestos, coexisting in the sub-strata at its mined source. This was the case for a mine in Libby, Montana USA, which supplied a large amount globally in the 20th Century.
Just like the asbestos coatings, it was applied with industrial-sized sprayers as insulation on the underside of roofs and in multi-storey ceiling tween-spaces on underside of floors. Used to achieve building fire-rating and a barrier against condensation, on steel and reinforced concrete beams/columns.
Occasionally sprayed externally as a façade, such as in front porch areas. Sprayed onto residential ceilings, particularly within blocks of flats.
While these older coatings are a risk, not all vermiculite is contaminated and should be sampled and tested to confirm the presence of asbestos.
Brands/products
- Gypspray
- Zonolite
- Neuchatel Asphalte Co
- Monokote
- Acoustical Plastic
- Morgan – Uniplastic
- Morgan – Unikast
- Referenced as vermiculite coating
Years of production/use
1924-1990 (absestos risk)
Residential uses
Ceilings, external facades on houses
Industrial uses
Ceilings, underside of roofs and in multi-storey ceiling tween-spaces (above suspended ceiling panels) on underside of floors
Be aware
Overspray and splash back often occurred at the site from the equipment, requiring clean-up. In isolated spaces there is likely to be debris around the sprayed area.
A professional sampling plan for older vermiculite coatings is important because it needs to be sampled in multiple locations, as some areas may be contaminated and others not. Detection of asbestos may depend on the concentration of a potential contamination or whether different batches of spray were mixed before application. A professional approach will also assess whether the ceiling material is actually a sprayed asbestos coating, rather than a vermiculite base.
