Fibrous cement sheets are more durable than drywall and easier to work with than concrete, and they have numerous applications in construction. Today, the fibers in cement sheets are usually made of cellulose, a substance found in plants, but for the first eight decades after fibrous cement sheets were invented, they were primarily made with asbestos.
Asbestos is a naturally occurring mineral that can be fluffed into a wooly consistency and mixed into building materials such as cement. Adding asbestos makes cement more durable, weatherproof and heat resistant, and because asbestos cement sheets are fireproof, builders initially considered them a much safer material than wood. Unfortunately, it is now well known that adding asbestos to cement also makes it highly toxic.
“Asbestos cement sheet” was once synonymous with “fibrous cement sheet,” and it has also been generically called “AC sheet” and “fibro.”
U.S. companies stopped manufacturing these types of asbestos products in the 1980s, but they are still popular building materials in developing nations such as India and China.
Common types of asbestos cement sheets include:
Corrugated asbestos sheets
Fibrous cement created an easy and affordable alternative to corrugated metal panels, which offer little insulation and inevitably rust over time. Corrugated asbestos sheets were used in the roofing and siding of all types of buildings, especially in factories and farms.
Because fibrous cement is much more water resistant than drywall, flat sheets of asbestos cement found their way into the interiors of homes and businesses as walls and underlayment for flooring.
Also called asbestos cement sheathing, “asbestos lumber” was not made out of wood at all. Instead, it was marketed as a superior alternative to wood. It was fireproof and electrically nonconductive, yet still soft enough to be worked like natural lumber. Asbestos lumber was used as a base for roofing and siding materials such as shingles and false brick facing.
In 1899, Austrian-born industrialist Ludwig Hatschek invented the process for creating asbestos cement, and eight years later Keasby & Mattison (K&M) became one of the first companies to produce corrugated asbestos sheets under Hatschek’s U.S. patent.
Workers pressed a mixture of cement, water and chrysotile asbestos between metallic plates with heavy pressure to squeeze out excess water and create a corrugated pattern, which appears as a series of parallel ridges that add strength to the cement sheets. K&M named its brand of corrugated sheets after the town of Ambler, Pennsylvania, where its factory was located.
The company promoted Ambler roofing and siding’s “comparative lightness, ease of application, weather and fireproof qualities, pleasing appearance and permanence,” and early clients included the Draper Company in Massachusetts, the Shenango Furnace Company in Pennsylvania and the Bell Asbestos Mines in Canada. When a fire broke out in one of the Bell mills, the asbestos siding and roofing reportedly contained the blaze, backing up K&M’s claims.
Over the following decades, several more companies began manufacturing corrugated sheets and sheathing made from asbestos cement. In the 1950s, the National Gypsum Company added corrugated asbestos roofing to its Gold Bond line of products, cementing the building material’s popularity with home builders, farmers and factory owners alike.
By the 1980s, the rising tide of personal injury lawsuits over diseases such as asbestosis and mesothelioma compelled manufacturers to finally phase out the production of asbestos cement products in the United States. However, despite the grim reputation of asbestos in developed nations, a quick online search will reveal asbestos cement sheets are still widely available for sale in other parts of the world.
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Careycel Insulated Sheathing
Careystone Corrugated Asbestos Cement
Careystone Flat Asbestos Cement
|Keasby & Mattison Company||
Ambler Asbestos Corrugated Sheathing
Ambler Corrugated Roofing and Siding
Century Asbestos Corrugated Roofing
|GAF Corporation||Panelstone Asbestos Cement Sheeting|
|National Gypsum Company||Gold Bond Corrugated Roofing|
|Johns Manville||Transite Corrugated Roofing and Siding|
Other companies that manufactured asbestos cement sheets include:
- Asbestone Corporation
- Asbestos Shingle Slate & Sheathing Co.
- Atlas Asbestos Company
- CertainTeed Corporation
- Durabla Manufacturing Company
- Flintkote Company
- Garlock, Inc.
- James Hardie Industries
- Philip Carey Manufacturing Corporation
- U.S. Gypsum
Asbestos cement sheets may pose a health hazard during installation, demolition, renovation or cleaning. These products were known to contain 10 to 40 percent asbestos, and when they are pressure washed, sanded, sawed, drilled, removed or otherwise disturbed, asbestos fibers may be released into the air to be inhaled by unsuspecting workers and residents. Time and weathering can also weaken these sheets, exposing the asbestos fibers imbedded in the cement to the elements.
High levels of toxic dust were often present in the factories and plants where these products were manufactured. As a result, former factory workers are at extremely high risk of developing an asbestos-related disease.
People at risk of exposure from asbestos sheets include:
- Construction workers
- Demolition crews
- Factory workers who manufactured the products
- Military personnel
- Do-it-yourself renovators
Many former tradesmen and factory workers have sued manufacturing companies over occupational asbestos exposure.
For example, former electrician Earl Gifford sued the National Gypsum Company in 1983 after he developed mesothelioma. From 1948 to 1952, Gifford had worked alongside carpenters using Gold Bond cement flatsheet while converting Army barracks into apartment and dormitory buildings. A Texas magistrate awarded him $80,000.
By 2001, these awards had gone from thousands to millions of dollars, as illustrated by Guadalupe Laguna’s lawsuit against his former employer, Johns Manville. From 1968 to 1981, Laguna had been a machine operator and pipe inspector at a factory in Stockton, California, that produced asbestos cement products. As compensation for the debilitating asbestosis he eventually developed, a San Francisco jury awarded him $2.3 million.
Many companies have had to set up special trust funds for victims of asbestos exposure to avoid being overwhelmed by the volume of lawsuits. For instance, a series of corporate mergers and sales left Armstrong World Industries responsible for all the asbestos exposure caused by Keasby & Mattison, and today claimants can seek compensation from the Armstrong World Industries Asbestos Trust, which has paid out hundreds of millions of dollars in claims since 2006.
Abating the Product
The U.S. Environmental Protection Agency (EPA) considers asbestos corrugated sheet to be a Category II, nonfriable material. The material should be abated prior to demolition or renovation. If the material is not damaged, it may be removed by driving the nails through the sheet or cutting off the nail or screw heads. Damaged asbestos sheets, however, are subject to much stricter regulations.
Each piece of corrugated sheet or sheathing should be removed whole and kept wet to prevent asbestos dust from getting into the air, and all materials should be disposed of according to the laws of each state. As a general rule, the EPA recommends all asbestos-containing materials be abated by licensed professionals.
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EPA. (2011). Demolition practices under the asbestos NESHAP.
Retrieved from: http://www2.epa.gov/aboutepa/about-epa-region-4-southeast
Gifford v. National Gypsum Company. (1985).
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Johns Manville. Corporation. (1948). Johns-Manville corrugated and flat transite.
Retrieved from: http://archive.org/details/Johns-manvilleCorrugatedAndFlatTransite
McCullough, J. & Tweedale, G. (2008). Defending the indefensible. New York: Oxford University Press.
Meany, O. (1915). Corrugated Sheet Asbestos Concrete.
Missouri Department of Natural Resources. (2009). Management of nonfriable asbestos containing materials.
Retrieved from: http://www.dnr.mo.gov/pubs/pub2156.pdf
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Retrieved from: http://www.nhmrc.gov.au/your-health/asbestos-related-diseases
- U.S. Bureau of Mines. (1905). Mineral resources of the United States. Washington D.C.: Government Printing Office.
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Last Modified October 1, 2018