Asbestos Roofing Slate

Asbestos roofing slates are flat, rectangular roofing tiles manufactured from asbestos cement — a compressed mixture of Portland cement and chrysotile asbestos fibres. Developed in the early 20th century as a mass-produced alternative to expensive natural slate, these artificial slates became one of the most widely used roofing materials in the world between the 1920s and the late 1990s.

The asbestos content in roofing slates typically ranges from 10 to 15 per cent by weight, providing the cement matrix with tensile reinforcement and flexibility that prevented cracking under normal roof loads and thermal cycling. The slates were produced in various sizes, thicknesses, and colours — from natural grey through to red, green, and blue — and could be textured to imitate the appearance of natural stone slate.

Asbestos roofing slates are found on millions of buildings worldwide. In the United Kingdom, they are particularly common on 1930s to 1960s semi-detached houses, bungalows, council housing, schools, and churches. In the United States, they were marketed as "asbestos shingles" and installed on residential properties throughout the northeast and mid-Atlantic regions. In Australia, they are found on both residential and commercial buildings from the mid-century era.

Like other asbestos cement products, roofing slates are non-friable when intact. The fibres are bound in a hard cement matrix and the risk of fibre release in normal service is low. However, roofing slates can be broken during maintenance work, re-roofing, or by storm damage. Walking on asbestos cement slates can crack them, and removing them by prying can snap the material. Any breakage generates dust containing asbestos fibres.

If your property has asbestos roofing slates, they can be safely managed in place provided they are in good condition. When replacement is needed, a contractor experienced in asbestos cement removal should carry out the work, carefully removing each slate whole and lowering it to ground level without breaking. Modern fibre-cement slates, concrete tiles, or natural slate are suitable replacements.