Testing for Asbestos
Kevin O’Connor finds a plaster expert to alleviate a homeowner’s asbestos worries
The interior walls of our house, built in 1924, are covered in plaster and lath. We’d like to rip out a non-load-bearing wall, but are concerned that there might be asbestos in the plaster. Should we have it tested first?
—Kelsey McClure, Bloomington, IL
Rory Brennan, the owner of Preservation Plastering in Brattleboro, VT, is an expert on all things plaster, and has helped out a number of times on This Old House TV. Here’s what he had to say about your concern.
“It’s not likely that your old plaster contains asbestos. Plaster is by its nature highly fire resistant, and I suspect that contractors would have been reluctant to pay more for an ingredient offering a minimal benefit in residential construction. The United States Gypsum Company did begin selling a bagged plaster-asbestos mix in 1920, but it was targeted for commercial construction, where fire codes were—and still are--—much stricter. Other manufacturers jumped on the asbestos bandwagon after World War II, and continued adding it to plaster (and to drywall and joint compound) until as late as 1976, when it was banned from use in building products.
“During that time, this mix remained primarily a commercial product, so your original 1924 plaster probably is safe. However, it is possible that the wall was repaired at some later time with an unsafe product. You might even be able to see evidence of those repairs. All of which goes to say that the safest approach would be to send plaster samples to a lab for testing before demolishing your wall.
“If the test shows that there’s no asbestos, you can proceed with the work without taking special precautions. But if your plaster does have it, do the right thing and hire an abatement contractor to handle the demolition and properly dispose of the waste. There’s no reason to risk your health or that of your family by ignoring this nasty carcinogen.”
Shown: The United States Gypsum Company was the first to start adding asbestos to plaster as a way to improve its fire resistance and workability, long before asbestos was recognized as a health hazard.