Why high-pressure washing is prohibited, what sealing a sound roof actually achieves, and how to tell when a roof is past the point where coating it makes sense.
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Asbestos cement roofing: what to do and what never to do
A corrugated asbestos cement roof is usually safe while it is left alone, and is made dangerous by exactly the three things people most want to do to it: walk on it, clean it and cut it.
The roof is fine until someone treats it like metal
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Corrugated asbestos cement roofing — the profile many Australians still call by its old trade name — is one of the most common bonded asbestos products left on houses, garages, sheds and carports. Weathered, it goes chalky and moss-grown and looks tired, and that appearance is what prompts most owners to act.
Three actions are the problem. High-pressure cleaning is the worst thing you can do to an asbestos cement roof: it strips the degraded surface and drives fibres into the air, the gutters and the soil around the house, and it is prohibited in every Australian jurisdiction. Cutting or drilling the sheets with power tools does the same thing at close range. And walking on it is a structural danger before it is a fibre one: weathered sheets are brittle and give way, which is why falls through roofs remain a leading cause of serious injury in this work.
What is generally permitted, and often sensible, is careful painting or sealing of a roof that is still sound, which binds the surface and buys years. The rules on how that is done — preparation, no abrasion, no pressure washing — are set by state regulators, and the honest answer for most roofs in poor condition is that sealing is a delay rather than a solution.
Replacement is Class B licensed work in practice for anything beyond a tiny area, because roofs are large, elevated, and impossible to keep below the homeowner threshold. It also has a second half that people forget: the insulation, dust and debris sitting in the roof space beneath the sheets, which is a separate question with a separate answer.
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Who is licensed to do it, what notification the job needs, what happens to the roof space underneath, and what a proper site looks like from the footpath.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NSW Government. Asbestos in NSW — the NSW Government asbestos portal
- WorkSafe Victoria. Asbestos — duties, licensing and safe removal