Asbestos in Flashing and Other Building Materials
Flashing is any piece of material used for water resistance in roofing or joints where perpendicular surfaces come together in building construction (for example, a house with gables protruding from a pitched roof). While most types of flashing is made from galvanized sheet steel, aluminum, copper or other form of metal, hidden flashing may be made from any number of materials, such as fabric or plastic sheet.
By weaving asbestos into fabric the flashing material became chemically inert (it would not interact with adjoining materials and potentially cause discoloration), more durable and fire resistant. In the early and mid-20th century, asbestos flashing became quite common because the asbestos was inexpensive and the fireproofing qualities were highly valued to guard against the risks of fire.
The most common type of asbestos used in construction materials like asbestos flashing was chrysotile. Although "new" uses of chrysotile (white asbestos) have been banned in the U.S., a thriving chrysotile mining and processing operation exists just north of the border in Thetford, Quebec. In addition, asbestos building products made in China, India and Mexico continue to enter the U.S.
Flashing Products Containing Asbestos
The following partial list of flashing products were known to contain asbestos:
|Product Name||Start Year||End Year|
|Celotex Everlastic Flashing Cement|
|Certainteed Asbestos Base Flashing||1968||1976|
|GAF Asbestos Combination Flashing|
|H.B. Fuller Flashing Compound 95-10||1960|
Hazards Associated with Flashing Products
As with many asbestos-based construction materials, new and intact asbestos flashing posed a certain degree of health hazard to the people who manufactured it (since they worked with the raw asbestos fibers, which are highly toxic) as well as to those who installed it if it needed to be cut during the installation process. Once the flashing was installed, had nails driven into it, was exposed to the weather, and began the normal process of wear and tear, the material also began to degrade. Those performing building repairs, roofing work or demolition work on older buildings, were likely to come into close contact with damaged asbestos. When asbestos is damaged individual asbestos fibers can come loose from their surrounding material. Airborne asbestos is easily inhaled, and once inhaled, can cause asbestosis, lung cancer, and malignant mesothelioma.Sources
Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)
Ching, Francis D. K. and Cassandra Adams. Building Construction Illustrated (3rd edition). (New York: John Wiley & Sons Inc., 2001)