Are Asbestos Cement Roofs Safe to Walk On?

Asbestos cement, usually shortened to AC, is cement reinforced with asbestos fibre and pressed into corrugated sheets. Farm sheds, factory units, lock-up garages and the back ranges of older shops all carry it. Paint, moss and years of weather make it hard to recognise by eye.

Is a fragile roof the same as a damaged one?

No, and that is the point people miss. A fragile roof is one that cannot be trusted to carry a person, whether or not it leaks. The sheets are brittle and they span wide gaps between the purlins, the horizontal beams underneath that carry the roof. A single step between two supports can snap a sheet clean through.

HSE also tells owners to assume that anything built or refurbished before 2000 contains asbestos. For a shed or unit of that age, that is the safe working position until a survey says something different. Treat the roof as fragile and as AC from the first moment anyone talks about going up there.

Most of what a roofer needs to see can be seen without touching a sheet. Begin at ground level with the building's edges, then work inwards.

What can you check from below?

Stand inside on a dry day and look up at the underside. Daylight through a sheet, rust-coloured drip marks on the purlins and damp patches on stored goods all point to a failed lap or a cracked sheet. Outside, look along the eaves for sheets that have slipped, bolts that have pulled through and gutters hanging low.

How does a roofer get up there safely?

Edge protection goes in first: guard rails along the eaves and the gable ends, which are the sloping end walls of the building, so nobody can walk off the side. Then boards or staging span across several supports, so body weight lands on the structure and never on a sheet. A platform lifted alongside the roof, or a tower at the eaves, shows every lap without anyone standing on it. If you manage the building, keep staff and other trades off the roof until that set-up exists, and tell them why.

Owners sometimes reason that a sheet which has sat in the weather for decades must have settled into something solid, or even toughened with age. HSE's wording leaves no room for that idea. Moss and lichen can hide hairline cracks, and a sheet that has only ever carried rain has never been tested with a person.

Why does HSE call weathered sheets non-licensed work?

That is a separate question about removal. HSE classes work on asbestos cement as non-licensed when the sheets are handled and taken off carefully without being broken up, and it says this takes in AC that has aged in the weather without being badly damaged. The sentence sorts the removal into a category. It says nothing about strength, and it does not make an old sheet safe to stand on.

HSE puts work that substantially damages or breaks up the sheets into a more demanding category, notifiable non-licensed work, and its example is dropping an AC roof. Broken sheets also shed dust and debris, which gives a second reason to keep boots off them and to avoid hurried repairs.

When a sheet has cracked or a lap has opened, the options are a careful local repair, overcladding with new sheets laid over the old, or stripping the lot. Which suits you turns on how sound the sheets and purlins are, what the building holds and whether anyone works beneath the roof, which is why the survey looks at all three together.

How do we approach an AC roof?

The survey comes first, taken from safe positions, and the photos in our findings show your own roof with the problem areas marked. When the sheets turn out to be AC, we flag it before any price is discussed, because the access, the method and the waste route all follow from it. One total price, in writing, comes once the survey is done.

Further reading: asbestos surveys before roof work, asbestos roof sheet disposal and fibre cement roof sheets for replacement options. The wider picture is on our commercial roofing page. To start, send the building's address, its approximate age and a few photos taken from the ground.