The short answer
Sometimes, yes. Overcladding means fixing new sheets over the old asbestos cement ones instead of taking them off. It can suit a roof in sound condition, but the old sheets stay fragile, the fixings must be planned so the material is not broken, and the extra weight needs checking. Removal is the cleaner option when the sheets are weathered or the frame is tired.
Leaving the old sheets in place sounds simple. Whether it is wise depends on their condition, the frame beneath them and what you plan for the garage later.
What overcladding actually involves
Overcladding leaves the existing asbestos cement sheets as a deck and lays a new weatherproof covering above them, usually profiled metal sheeting on new supports. The old roof is left whole instead of coming off. That avoids handling the material at the start, which is the point of the method and the reason owners ask about it. It also means the old sheets stay in service as part of the new roof, so their condition matters as much as the new covering does.
Is leaving the asbestos in place always lower risk?
Not automatically. The new roof has to be fixed to something, and fixing through or across fragile sheets means working on a surface that HSE describes as always fragile. Drilling, cutting and the weight of people and materials all disturb the old sheets. The method has to be planned so the sheets are not broken and nobody stands on them, with crawling boards or a platform spreading the load.
Where the existing roof is cracked, mossy and brittle with age, overcladding often means handling more of the material, not less, so the survey checks sheet condition before any method is priced. Our page on asbestos garage roof removal compares the other route.
What HSE says about asbestos cement
On HSE's page about non-licensed work, asbestos cement sits in the lower-risk group so long as the material is handled or removed carefully, without breaking it up. Cement that has weathered but is not otherwise badly damaged is included. Work that substantially damages the sheets lands in a different group, notifiable non-licensed work, where health records are kept for 40 years.
How do I know the roof is asbestos cement?
You usually cannot tell by looking. For a building built or refurbished before 2000, HSE's guidance is to assume asbestos is in it. Analysis of a small sample by a laboratory gives a firm answer, and a roofer can point you to one. Until the result comes back, treat the whole roof as asbestos.
All of this is general guidance for your reading, not legal advice on your roof. Whether overcladding is acceptable on your garage is a judgement made on site, with the method written down beforehand. If the survey shows that fixing the new roof would break sheets, you hear it from us at once, and the removal route is priced instead, with careful handling from first sheet to last.
Weight, structure and Building Regulations
A second roof sits on a frame built for one. Profiled metal is light, but it still adds load, plus battens or support rails, plus snow and wind. Approval under the Building Regulations is needed when a new covering raises the roof's covering weight by 15 per cent or more, and the Planning Portal tells owners to get a structural opinion first, from an engineer or a surveyor. Overcladding can reach that mark on a tired frame.
Does overcladding need building control?
Possibly, which is why the question goes to your building control body before work starts. Fire behaviour is the other trigger: a new covering that performs very differently in a fire from the existing one also needs approval. For Taunton addresses, Somerset Building Control on 0300 303 7790 will advise.
The purlins carrying the sheets matter as well. Steel or timber purlins that have rusted or rotted cannot take a second skin safely, and that cannot be judged from the drive. We check them from inside the garage and from a safe working platform, and send you photos of what is found. Our repair or replace guide covers the wider decision.
Overcladding or removal: how to choose
Overcladding can make sense where the old sheets are sound, the frame is strong, the garage will stay a garage and the asbestos will be dealt with at some later date. It keeps the roof intact now, but the asbestos is still there, and whoever removes or demolishes the garage later will have to deal with it.
When is removal the better choice?
When you want the question closed for good. New sheets over old ones leave a double roof with a trapped void, a fragile layer beneath the new covering and an asbestos question that returns whenever the garage is surveyed, converted or sold. A roof with the old sheets gone and a clean frame is simpler to insulate, ventilate and convert, and it makes a later buyer's questions easier to answer.
Whichever route suits, the waste rules apply. Anything that does come off is double-wrapped and labelled, then moves under a consignment note with a registered carrier, never into a skip. The garage and asbestos roofs page lists our work, and our answer on removing asbestos yourself explains why that job needs care. Book a survey and we compare both routes for your garage, show you photos of the sheets, and put one price in writing for whichever you pick.
More on covering asbestos roofs
Does overcladding make an asbestos roof safe?
It covers the old sheets, but they remain asbestos cement and remain fragile. The risk moves rather than vanishes: it returns whenever someone cuts, drills or removes the roof in future. Overcladding is a decision about leaving the material alone, not a way of making it harmless.
Will overcladding trap condensation?
It can. Two layers with a void between them create a surface where moist air condenses if the garage is warm and damp. Ventilation of the void and the build-up of the new roof have to be designed together, and an uninsulated, unheated garage carries less risk than a converted one.
The full picture: Garage and asbestos roof replacement in Taunton ยท More short answers