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Asbestos in Siding and Other Building Materials

The most common type of asbestos siding used in home and building construction was known as transite. This is essentially ordinary portland cement to which asbestos fibers have been added. The presence of asbestos fiber created a type of cement siding that could be made into relatively thin sheets that retained tensile strength and remained durable while providing fire-resistance.

Originally, transite was a brand name, used for a proprietary product manufactured and marketed by the Johns-Manville Corporation. Eventually, the name became a generic term for the material, which was used not only for siding, but roofing, furnace flues, wallboard, drainage systems and water pipes, HVAC ducts and even walk-in coolers used in restaurants and supermarkets.

Until the 1980s, transite siding and other products could contain up to 50% asbestos fiber. The use of asbestos has been phased out since that time; transite manufacturers today use crystalline silica. This asbestos substitute is not much better, however; according to the International Agency for Research on Cancer (IARC), exposure to crystalline silica can also cause cancer as well as silicosis, a disease similar to asbestosis.

Siding Products Containing Asbestos

The following partial list of siding products were known to contain asbestos:

Product Name Start Year End Year
Boise Cascade Insulite Asbestos Siding Shingles
Celotex Careystone Roofing & Siding
Flintkote #60-w Waveline Siding
Flintkote #70-T Tapertax Siding
Flintkote #70-W Straight Edge Siding
Flintkote #70-X Stri-Color Siding
Flintkote Asbestos Cement Siding & Roofing
Flintkote Siding
GAF Ruberoid Aristo Insulating Siding
GAF Ruberoid Dura-Color Colonial Siding
Johns Manville Transite Siding 1906 1975
National Gypsum Chromashake Siding 1954 1968
National Gypsum Chromatex Siding 1954 1968
National Gypsum Classic “32” Siding 1954 1968
National Gypsum Classic Shake Siding 1954 1968
National Gypsum Deeptex Siding 1954 1968
National Gypsum Gold Bond Siding
National Gypsum Sussex “32” Siding 1954 1968
National Gypsum Woodgrain Siding 1954 1968

Hazards Associated with Siding Products

Asbestos-contaminated transite siding is still present in thousands of older structures throughout the U.S. If the material is intact, it presents little in the way of hazard to renovators and demolition crews. When broken, cut or sawed however, asbestos dust is released into the air (asbestos materials in this state are considered friable).

While it is possible to identify these asbestos-containing materials by sight in many cases, most state environmental regulations require that old buildings slated for renovation or demolition undergo a thorough inspection before work can begin. If the presence of transite siding is confirmed, it must be removed and disposed of by a licensed asbestos abatement contractor, mainly because many steps must be taken in order to protect the public, and the disposal of asbestos waste is subject to strict environmental regulations.



Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)

N/A. "Guide to Identifying Asbestos Transite Chimneys, Flues & Pipes in Buildings." Inspect-A-Pedia ( Retrieved 20 January 2011.

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