Is an Asbestos Garage Roof Dangerous?

Why intact sheets are a low risk

Most older garage roofs made of corrugated grey sheet are asbestos cement. The asbestos is bound into a hard cement matrix, so fibres do not drift off a sound sheet in the way they would from loose lagging or sprayed coatings. A roof that is whole, dry and untouched is generally managed by leaving it in place and checking it now and then. Nobody needs to panic, and nobody needs to rip it off tomorrow.

Not every garage roof of that age is asbestos, though, and you cannot tell by eye. Our page on how to tell whether your garage roof is asbestos covers the clues, and testing a garage roof for asbestos explains how a sample is taken and analysed. Until you know, it is sensible to treat grey fibre cement sheet from a pre-2000 garage as though it contains asbestos.

What turns a sheet into a hazard

Damage is what matters. Asbestos cement weathers over many years: the surface erodes, moss grows on it and the sheet gets brittle. A roof in that state sheds fine particles as it ages, and a cracked or holed sheet is worse. Disturbance by people is the bigger problem. These are the things that turn a quiet roof into a hazard:

• Pressure washing or scrubbing off moss, which grinds the surface and throws the debris around the garden.
• Drilling or screwing through sheets to hang a solar panel, aerial or light.
• Walking on the roof, since old sheets snap underfoot and drop you into the garage.
• Smashing the roof down in lumps to save time, then sweeping up the dust.
• Burning or disposing of broken pieces with ordinary rubbish.

The harm from asbestos comes from breathing the fibres, and it shows up many years later, which is why casual handling is a bad idea even when the job seems small. A damp sheet breaks more cleanly than a dry one, but wetting is no substitute for proper controls.

Signs the roof is getting worse

A quick look from the ground, with a camera and a zoom lens, tells you a lot. Heavy moss or lichen that has taken hold means the surface is eroding underneath. Sheets with chipped corners, cracked ridges or bolt holes that have pulled through are ageing. Pieces on the floor of the garage, on the car or along the base of the wall are a clear sign that material is coming off. Sagging in the middle of a sheet suggests a purlin (the timber or steel beam the sheets rest on) has moved or rotted, and a sheet that flexes is a sheet that may crack.

None of this means an emergency, but it does mean the roof is moving from low risk towards something you should plan for. A roof that is leaking is also telling you the sheets or their fixings have failed, and wet timber below may no longer hold the weight of a person. Photograph what you see each season so you can show the change, and avoid climbing up to look closer.

What to do if yours is damaged or you want it gone

If a sheet is cracked, holed or crumbling, keep people and pets away from the area beneath it, do not sweep or hose the debris, and get advice. Sealing is sometimes discussed, and sealing an asbestos roof is worth reading before you try it. If you plan to replace the roof, read whether you can remove it yourself first, because the rules on handling and disposal apply to householders too. HSE guidance on non-licensed asbestos work is at hse.gov.uk.

For a garage roof the usual choices are to leave it and monitor it, to overlay it with a new covering where the structure and the sheets suit that, or to take the sheets off carefully and fit a new roof. Our garage roof replacement service starts with a free survey. We photograph the roof so you can see its condition for yourself, tell you plainly whether it can stay, and give you a fixed written quote if it cannot.