Asbestos Cement Downpipe

Asbestos cement downpipes are cylindrical pipes, typically 65 mm to 100 mm in diameter, manufactured from a mixture of Portland cement and chrysotile asbestos fibres. They were produced to carry rainwater from roof gutters down to ground-level drains and were a standard component of the rainwater goods system on buildings constructed from the 1930s through to the late 1990s.

The asbestos content in downpipes typically ranges from 10 to 15 per cent, with chrysotile being the predominant fibre type. The addition of asbestos gave the pipes greater tensile strength, resistance to frost damage, and durability compared to plain cement. These properties made asbestos cement downpipes popular in climates prone to freeze-thaw cycles.

Asbestos cement downpipes are found on residential properties, schools, hospitals, commercial buildings, and industrial units throughout the United Kingdom, Australia, New Zealand, South Africa, and parts of Europe. They are particularly common on post-war council housing estates and 1960s-era system-built properties.

While intact and undisturbed, asbestos cement downpipes present a low risk because the fibres are bound within the cement matrix. However, the pipes are exposed to the elements and over decades can become weathered, cracked, or damaged by impact. Weathered sections develop a chalky surface where asbestos fibres begin to be exposed. Physical damage, such as from ladder strikes, lawnmowers, or accidental impacts, can fracture the brittle material and release fibre-laden dust.

If you suspect your building has asbestos cement downpipes, avoid disturbing them. A professional asbestos survey can confirm the material type through sampling. When replacement is needed — for example during renovation or because of damage — a licensed asbestos removal contractor should carry out the work. Replacement is straightforward using modern PVC or cast-iron effect downpipes, which offer superior longevity without health risk.