Asbestos overlay
Can an asbestos garage roof be overlaid instead of removed?
An overlay leaves the old sheets under a new covering. Whether that is sound for your garage is a survey question, and part of it is a weight question.
The short answer
Sometimes, where a survey finds the old sheets and the structure under them sound enough to carry a second covering. It is never a rule of thumb. The asbestos stays on the building, the roof carries both coverings, and the Planning Portal's 15 per cent weight trigger and Approved Document A's more than 15% loading test both apply. Removal is the other route, and the choice is made roof by roof.
4 min read · Part of Garage roofs
What an overlay is and is not
An overlay fixes a new covering above the existing roof, with the old sheets left up. The asbestos is covered, not removed. HSE's words are "If the building was built or refurbished before 2000, assume that there is asbestos in it", and that assumption stays with the building afterwards, so a later repair, a new opening or demolition still has to deal with the material under the new roof.
Under HSE's A14 guidance, AC roofs are always fragile. A fixing scheme that needs people on the old sheets, or a framework built from above, has to account for that, and the survey has to show that the fixings can go in without breaking the sheets. Our page on how to tell if a garage roof contains asbestos covers how the material is confirmed before any plan is made.
An overlay is a different job from a repair, and from replacement. It sits between them, it suits some roofs and not others, and it never turns an asbestos roof into an ordinary one.
What the survey looks at
The old sheets, the frame beneath and the building around them each decide the answer.
- The sheets: are they whole, or split along the edges, lifting or flaking?
- The frame: can the purlins and rafters carry both coverings?
- The weight: how heavy is the new covering when added to the old?
- The fixings: can they be made without breaking the sheets?
- The eaves and gutters: will the new roof drain to a sound outlet?
On weight, the Planning Portal says approval is needed if a covering adds 15 per cent or more to the roof covering's weight, and its advice is to involve an engineer or surveyor for the structure first. Approved Document A calls it a significant change in roof loading when the loading upon the roof is increased by more than 15%. An overlay adds a covering and removes none, so the frame carries the full weight of the new layer on top of the old one, and that is the figure to test.
Building control can say which route applies to your address, and the answer is better asked for before the quote than after it. Photos of the sheets, the frame and the eaves go into the survey notes, so the decision can be checked later by anyone who reads them.
Overlay and removal compared
Neither route is a fix for every garage. The differences are plain.
| Point | Overlay | Removal |
|---|---|---|
| Asbestos | Stays on the building | Leaves with the waste |
| Weight on frame | Both coverings | New covering only |
| Waste route | None now | Lockable skip, consignment note |
| Later roof work | Asbestos still there | Asbestos gone |
The table shows why an overlay is tempting: no waste to move today and no stripping. It also shows what is put off, which is a roof that is still fragile and still asbestos at the next job.
MyJobQuote's average for asbestos removal on a UK roof is around £2,750, and its garage roof replacement range for 2026 is £750 to £3,500. Those third-party averages explain why an overlay is worth weighing. They do not decide it. If the survey finds the frame sound and the sheets whole, an overlay may be a fair option for a garage with a short future. For a garage you plan to keep for many years, the asbestos stays a question for every later job and every later owner. Our page on the disposal route in Kent explains what removal involves.
How the survey ends
We survey the garage, confirm the material of the roof and tell you plainly which route fits: overlay, removal or leaving it alone for now. Where an overlay is sound, that is the verdict, and where it is not we give the reason, with photos of what we found.
If the sheets are damaged or the frame is weak, an overlay would only cover a problem. In HSE's list, notifiable non-licensed work includes asbestos cement sheeting that fire or flood has broken up, so the plan changes, and the notes from the survey record which case applies.
One written total price follows, and the total should name VAT and scaffold as in or out. Ask for the survey notes in writing too: they say which sheets were checked, what the frame looked like and what the fixings plan is. Put it beside the garage roof replacement cost guide before you decide, and ask what each route leaves behind as well as what it costs on the day. The garage roofs hub covers every option on one page.
More questions
Does an overlay get rid of the asbestos risk?
No. The sheets stay in place under the new covering, so any later work on the roof or the building still deals with them. HSE's rule, "If the building was built or refurbished before 2000, assume that there is asbestos in it", carries on applying, and the sheets stay fragile.
Does an overlay need building regulations approval?
It can. The Planning Portal gives approval triggers for re-roofing, including a covering 15 per cent or more heavier, and Dover District Council lists roof coverings even like for like. Building control can say which route applies to your address. Ask before the quote is accepted, not after the work has started.
Tell us what's wrong with the roof.
You'll get one written total price.