Fragile asbestos roofs
Can you stand on an asbestos garage roof?
The short answer
No. HSE guidance on asbestos cement describes these roofs as always fragile, so a sheet can give way and drop you onto the floor below. A cracked sheet also puts dust into the air. Keep off the roof, keep ladders from resting on the sheets, and let a roofer inspect from the edge and from inside the garage.
Why old garage sheets fail underfoot, what a crack does to the material, and the safer ways to check a roof that worries you.
Why a sound-looking sheet still gives way
An old fibre cement sheet spans from one purlin to the next, which is a timber or steel rail running across the roof. A person's weight lands mid-span, where the sheet is weakest. Years of weather leave the material brittle, so a sheet that seems sound when seen from the drive can give way at the first footstep.
HSE's guidance A14 is blunt on the point: asbestos cement roofs are always fragile. Its page on fragile surfaces puts fibre cement sheeting and rooflights in one group. Moss and lichen make things worse, because a mossy sheet hides hairline cracks and turns slippery when damp. Nobody can judge the strength of a roof by looking down at it, however sound it appears from an upstairs window.
The danger is a fall through onto whatever stands below, usually a car, a workbench or a concrete floor. Garage roofs are low, yet a drop through one still hurts, and the broken pieces come down with you.
Rooflights and patched sections
Plenty of garages have one or two translucent sheets set into the roof to let light in. HSE lists rooflights among fragile surfaces, and in a garage they are often the oldest and most brittle part of the roof. Moss can hide them completely, so they are easy to step on by mistake.
Patched areas deserve the same caution. A garage that has had a felt repair, a bitumen strip or a replacement sheet may carry a mix of materials now, and each one takes weight differently. If you cannot tell what is under your feet, assume none of it will hold you.
The same goes for a lean-to or a porch roof made of the same stuff. Our page on how to tell if a garage roof is asbestos explains how to work out what you have before anyone climbs near it, and how to avoid disturbing it while you look. It also helps to know the age of the garage and of any extension.
What a crack does to the asbestos
There is a second reason to stay off, apart from the fall. Asbestos cement that has weathered but is not otherwise badly damaged sits, in HSE's terms, inside the non-licensed category if the handling is careful. Stand on it, crack it, or let a ladder crush an edge, and you begin turning it into something worse.
Once material breaks up and fills the air with dust, the work moves into the notifiable category, with a notice to the regulator before it continues. That changes the cost, the method and the paperwork, and it is avoidable if the roof is left alone until someone has planned the job.
Your own health comes into it as well. Per HSE, a building that dates from before 2000 should be treated as if it contains asbestos, so a garage of that age is worth treating with respect before any test result arrives.
How a roofer inspects one without standing on it
We look at these roofs without putting weight on them. The usual approach is to inspect from the ground, from a ladder at the edge, and from inside the garage, where daylight showing through cracks, lines of staining and rusted bolts tell us a lot. Photographs are taken at each stage so each conclusion can be checked against what we saw.
If work does have to go onto the roof, it is planned first, so that weight is spread and supported and nobody relies on the sheets alone. That planning is part of the price of an asbestos roof job, and it is a good question to put to any firm you are comparing.
After the survey you receive the photographs and a plain repair-or-replace verdict. What we recommend is the least work that will put the fault right, and the price is set out in writing as one total, with its coverage stated in plain words.
What to do if you are worried about the roof
Start from the inside. Look up at the sheets on a bright day. Light through a crack, a sagging sheet, or water marks around a line of bolts all tell you something. If the gutter is overflowing, a ladder at the edge is a better place to look from than the roof itself, but keep the ladder off the sheets.
If you think the roof is leaking, read our page on a leaking garage roof first. A drip is often condensation, not a break, and nobody needs to go onto the roof to deal with that.
When you are ready to talk to someone, send us photographs taken from the ground. Where water is coming in, we make the roof safe before we talk through the options, including cost and consent questions. The garage roof replacement page gives the wider picture of what a full re-roof involves.
Related questions
Staying off asbestos sheets
Is it safe to clear moss from an asbestos sheet roof myself?
It is better left. The roof is fragile, so you risk falling through, and scraping or brushing a weathered sheet disturbs the very surface you want to leave alone. Ask a roofer to inspect the garage first and to say whether the moss needs attention at all.
Can a ladder lean against asbestos sheets?
Avoid it. A ladder pressing on the edge of a brittle sheet can crack it, and a cracked sheet is harder to lift off whole. Rest the ladder against a sound wall or fascia instead, or use a free-standing ladder with a helper at the foot.