Asbestos in Roofing Materials

A crew working on a high school in the Maritimes had to stop work and call in asbestos specialists when ACM (asbestos containing materials) were found on the roof.

Now, this may seem far away from the GTA and asbestos in the roofing tiles of an old institutional building wouldn’t come as any surprise. But – the ACM wasn’t in the roofing tiles themselves. It was in the tar that had been used to install and also subsequently patch the roof over the years. In the case of the Halifax high school, tar particles fell into the library and other rooms after work done on the roof. The tar was found to contain 5 percent asbestos, which was common in formulations before the 1980’s.

ACM in Sealant & Caulking
Asbestos was added to roofing tar, caulking and other sealants because of its fire retardant properties, most often in the 5 to 10 percent range. Although new formulations don’t contain the material, as anyone who’s owned an older home knows, many homeowners don’t remove the old material when adding the new when it comes to roofing. Many roofs have layers of older shingles and other materials underneath newer layers.

  • If you’re installing a new roof, who knows what you might encounter?

ACM is considered friable – or inhalable and therefore dangerous – if it contains more than one percent asbestos and it can easily be crumbled or pulverised by the human hand.

Asbestos itself is nearly indestructible. However, in ACM, it’s the other materials which most often deteriorate over time, leaving friable asbestos. Any ACM may in fact become friable under the right conditions. Something you may not even think about – such as kids bouncing a ball off the roof – can leave dust that is suspended in the air for some time afterwards and leave you or your loved ones exposed.

Any ACM should be removed if:

  • You plan on making renovations or remodeling in the foreseeable future
  • There is any damage at all – encapsulation is not a safe option.

Here is where you may find ACM in those odd places you don’t expect:

  • Roofing tar is typically used on flat roofs and often to fix leaks. It consists of coal tar in a formulation with petroleum byproducts and as its name suggests, is a very dark brown or black. Coal tar itself is a byproduct of the petroleum making process, refined for use in roofing tar.
  • Coal tar roof cement is used for roof repairs in a formula thickened with fibres that can seal or bond with the existing surface. Pre-1980’s roof cement most often contained asbestos, along with solvents and other materials. If the cement is still pliable, it should not pose an immediate danger however if it has dried out and/or is cracked, it becomes friable. Use caution and do not scrape it.
  • Clay based materials such as plumbing putty, window putty and caulking also often contain asbestos in older formulations. This material is friable and should be protected from water damage – better yet, removed. Avoid scraping dried out material.

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