Corrugated asbestos cement sheet is the most widespread asbestos product still on British buildings: garages, sheds, farm buildings, workshops, lean-tos and industrial roofs. It is a hard, dense material with the fibres bound into cement, which is why work on it is normally non-licensed. It is also brittle and fragile, which is why the two dangers on the job are falling through it and breaking it.
What the sheeting is
Portland cement with asbestos fibre as reinforcement, pressed into corrugated or flat profiles. It weathers to a grey or green tinged surface, often with moss along the laps. Because the fibres are bound in cement it releases very little while it is intact, and a great deal when it is broken, cut, drilled or power washed.
Fragile roofs
Asbestos cement is a fragile material in the sense the construction industry means: it will not reliably carry a person, and falls through such roofs are a long standing cause of construction fatalities. Any quote for work on it has to name the access and edge protection, and a price that only works if somebody walks the sheets is a price for an unsafe job.
Coming down whole
Sheets are unscrewed and lowered rather than dropped or smashed. That is slower and it is the entire reason a compliant quote costs more than an incompetent one. Breaking sheets turns a controlled job into a contaminated site and turns a modest waste bill into a remediation.
Waste and cost
Cement sheet is dense, and disposal is usually charged by weight, so the waste line on a large roof can rival the labour. Ask for the disposal measure and route, and for a copy of the consignment note when the work is done. If the sheets are sound and the roof is not being altered, leaving them in place and managing them is a legitimate answer.
Questions people ask about asbestos roof sheets
Can asbestos cement sheets be pressure washed?
No. Power washing erodes the cement matrix and releases fibres, and it is one of the most common ways an intact roof becomes a contamination problem.
Can I overroof rather than remove?
Covering a sound asbestos cement roof is done, and it leaves the material in place and undisturbed. It has to be recorded, because the next person to open that roof needs to know what is under the new covering.
Is sheet removal licensable?
Work on asbestos cement is normally non-licensed work. It still has to be done competently, with the right access, the right waste route and the right paperwork.