Common in homes built in the 20th century is black mastic used as tile or linoleum adhesive. When you remove that floor covering to make way for new flooring, you may encounter it and wonder if it is safe to remove.
One wrinkle in this question: black mastic often contains asbestos. Asbestos has been proven to cause a life threatening condition called mesothelioma.
How can you know if your floor's adhesive contains asbestos?
If so, what is the best way to remove it?
What Is Black Mastic?
Mastic is the name for a type of flooring adhesive. Organic based, derived from a tree, mastic was cheap enough to use in large quantities for flooring. Asphaltic cutback adhesive was a similar flooring product that looks the same and also contains asbestos.
It is commonly thought that asbestos was added to the compound to deter fires. While this would have a residual effect, its main purpose was to make the product more durable. Asbestos is a highly fibrous material, and these fibers interlock to help form a solid material.
What Does it Look Like?
You will only see black asbestos mastic after a floor covering has been removed.
It will lay flat against the subfloor--no ridges, bumps, or gaps of any significance--with faint embedded swirls from its initial application.
No asbestos fibers will be visible to the bare eye.
If you were to vigorously sand it (not recommended), it would become thick and tar-like from the heat.
Does My Floor Have Asbestos-Based Floor Adhesive?
Containing between 15% and 85% asbestos, these adhesives were manufactured mostly in the first half of the 20th century.
However, some companies produced asbestos adhesives as late as the period between 1976 and 1984.
So, if your house was built or remodeled around 1984 or before, there is a chance that your mastic adhesive may contain asbestos.
Companies and Brands
The Peterson Firm LLP, a Washington DC law firm that deals with mesothelioma cases, notes that the following companies manufactured adhesives containing asbestos:
- 3M (Minnesota Mining and Manufacturing Company)
- American Biltrite
- Amtico Floors
- A.P. Green Industries
- Armstrong World Industries
- Asbestos Corporation, Ltd.
- Celotex Corporation
- Crown Cork and Seal
- Congoleum Corporation
- GAF Corporation
- Garlock Packing Company
- Johns Manville
- Mobile Oil Corporation
- National Gypsum Company
Prominent brands of asbestos-laced floor adhesive made by these companies are listed below. In some cases, you may find old cans of adhesive left behind by previous owners in basements or workshops.
- Armstrong S-89 Adhesive
- Armstrong S-90 Adhesive
- Atlas Stove & Furnace Cement
- Carey Fibrous Adhesive
- Empire Ace Fibrous Adhesives
- J-M Fibrous Adhesive Cement
- Crown Coat Cement
- Gold Bond Laminating Adhesive
Is It Safe?
Yes and no. Yes if left alone and encapsulated. No if abraded so that its fibers are released.
Unless the floor is removed, you will have no safety concerns. The only state in which asbestos is truly safe is when it is not exposed to activity that may abrade it--such as sanding it or even walking on it over time.
Unless the floor covering is valuable and worthy of restoration, the most efficient and safe thing to do is cover it with underlayment and install the floor covering on the underlayment.
In fact, some floor coverings--ceramic and porcelain tile, laminate, hardwood--can be installed directly on top of the tile--no underlayment required.
The worst activity would be to attempt to grind it off with a drum sander or to try manually scraping it off.
Because mastic and asphaltic cutback adhesive are so thick, gummy, and difficult to remove, there is practically way to remove it safely.
Other Areas That May Contain Asbestos
As for other parts of your house that might contain asbestos, you may want to check to see if your attic insulation contains asbestos.
Pipes are often wrapped in asbestos. You should have to worry about exposed pipes under sinks, though. Exposed pipes in crawlspaces and basements should be your main concern.