The short answer
If the roof is sound and dry, leaving it alone is often reasonable. If it has small cracks, repair may work. If it’s leaking, badly weathered or breaking up, removal is usually the better long-term answer. Whatever you choose, don’t jet-wash it, don’t sand it, and don’t walk on it.
Leave it and monitor
HSE’s advice to homeowners is that materials in good condition, unlikely to be damaged, can be left and checked from time to time (HSE’s asbestos FAQs). For a garage or shed roof that keeps the rain out, that may be all you need. Look for new cracks, slipped sheets, leaks and heavy erosion once or twice a year, from the ground or a ladder that isn’t resting on the sheets.
Repairing damaged sheets
HSE has a task sheet (A13) for trained workers repairing damaged asbestos cement, for example sealing small cracks or holes. It’s non-licensed work, but still needs a risk assessment, training and controls. Repair suits small, local damage. It won’t fix a roof that is brittle all over or failing at every fixing.
Painting or coating
Painting can seal a weathered surface and slow erosion. HSE task sheet A16 covers painting asbestos cement and says:
- wipe dusty surfaces with a damp rag first
- “never prepare surfaces by sanding or rubbing down”
- apply paint “preferably by low-pressure spraying”, or gently by brush or roller without working one area hard
Painting is a form of encapsulation. It changes how the roof looks, but the asbestos is still there and the paint needs maintaining. See encapsulation or removal.
Cleaning moss and lichen
This is where people most often get it wrong. HSE task sheet A12 covers cleaning weathered cement roofing and says “only in exceptional circumstances is high-pressure jetting appropriate”, and then only by a specialist contractor. Its method for trained workers keeps the surface wet, removes growth by gentle scraping and uses a low-pressure sprayer for biocide.
A pressure washer or wire brush strips the surface and spreads fibres and slurry over the garden, gutters and neighbouring property. If the roof is very mossy, it may be a sign it is near the end of its life anyway.
Overcladding
Overcladding means fixing a new roof covering over the old sheets, leaving the asbestos in place underneath. It avoids removal and disposal costs, but:
- the structure has to carry the extra weight
- fixing through the old sheets disturbs them, so it needs the same care as other non-licensed work
- the asbestos is still there for anyone who demolishes or alters the building later, so keep a record and tell future owners
It’s more common on larger industrial roofs than small garages.
Removing and replacing
Careful removal of cement sheets is normally non-licensed work. It deals with the problem once, and the new roof can be whatever suits you. Costs are covered in our garage roof removal cost guide, including why the new roof should be quoted separately. We remove asbestos roofs. Ask any contractor whether they also fit the new roof, or whether you’ll need a roofer for that part.
The fragile roof risk
Whichever option you choose, the biggest immediate danger may be the fall rather than the asbestos. HSE’s task sheets say cement roofs “are always fragile and cannot bear weight” and tell workers to take precautions to avoid falls. Never stand or kneel directly on the sheets, and don’t rely on the purlins. Professionals use platforms, staging or work from below or from the side.
How to decide
| Roof condition | Usual option |
|---|---|
| Sound, dry, mossy but not eroded | Leave and monitor |
| One or two small cracks or holes | Repair by trained workers |
| Weathered surface, no leaks, long life wanted | Paint or coat by HSE method, or remove |
| Leaking, brittle, broken or storm-damaged | Remove and replace |
| Fire-damaged or collapsed | Removal, likely notifiable non-licensed work |
Quick answers
Can I jet-wash an asbestos roof?
No. HSE says high-pressure jetting is appropriate only in exceptional circumstances, by a specialist contractor.
Does painting make it safe?
It can seal the surface and slow weathering, but the asbestos remains and the coating needs looking after.
Can you inspect my roof?
Yes. We can look at the roof, take a sample if needed and quote for removal. Ask us for a quote.
This guide is general information, not legal advice. For the law itself, see the Control of Asbestos Regulations 2012 and HSE’s asbestos pages. Not sure what you’re dealing with? Ask us.