History of Asbestos Cement Roofing

Asbestos cement (also called fibro, AC sheet or by trade names such as Eternit) is a composite of cement reinforced with asbestos fibres, pressed into thin sheets. In the 20th century it was one of the world's most widely used roofing materials, made into corrugated sheets, flat slates and shingles. Its decline followed recognition that asbestos fibres cause fatal diseases.

Invention

The Austrian industrialist Ludwig Hatschek patented the production process in 1900 (some sources give 1901). He mixed roughly 90% cement and 10% asbestos fibre with water and ran it through a machine adapted from cardboard making to form thin, strong sheets. In 1903 he named the product Eternit, from the Latin aeternus, "eternal". Rather than build most factories himself, Hatschek sold licences, and by 1910 Eternit factories existed in many countries.

Spread

Asbestos cement was cheap, light, fire-resistant and watertight. Products included corrugated roofing sheets (such as the "Super Six" profile), flat sheets, pipes and moulded items, and slates and shingles imitating natural slate. It was used extensively for quick military buildings in the Second World War and became a common affordable cladding afterwards. Australia and New Zealand were among the heaviest users; there James Hardie was the main maker until the mid-1980s. On roofs it was particularly common on industrial, farm and garage buildings.

Health and bans

By the 1970s, exposure to asbestos was widely linked to asbestosis and mesothelioma. Weathering, cutting and drilling release fibres, and roof sheets are especially exposed to erosion. From the 1970s asbestos use became progressively restricted in many countries, and cellulose and other fibres were developed as replacements in the 1980s. Asbestos-containing fibro has since been banned in several countries, including Australia, though asbestos is still used in building materials in some others.

Legacy

Many asbestos cement roofs remain in place. Because cutting, drilling and weathering release fibres, disturbing old sheets carries health risks, and removal is regulated in many countries. Modern fibre cement uses the same Hatschek process with non-asbestos fibres, and the Eternit trademark survives with the Belgian group Etex.

National bans

Bans came at different times. Great Britain banned white (chrysotile) asbestos in 1999, Australia banned the import and use of all asbestos from 31 December 2003, and Canada prohibited most asbestos products from 30 December 2018. In the United States, the Environmental Protection Agency finalised a ban on the ongoing uses of chrysotile asbestos in March 2024. The Australian ban did not cover materials already in place, and in many countries existing asbestos-cement roofs may stay until they are removed under regulated conditions.