Question answered
Can you walk on a slate roof?
The short answer
You should not walk on a slate roof. Slates are thin and brittle, and a boot concentrates your weight on one small area, so a slate can crack without any sign from above. Wet or mossy slate is also slippery, and a fall from a roof can be very serious. Roofers use roof ladders, crawling boards or scaffold to spread the load and stay safe.
Slate looks solid from below, but each slate is a thin plate resting on a batten. Standing on one can break it, and slate is slippery, so the sensible answer is to stay off.
Why a boot breaks a slate
A slate covering is built to shed rain, not to carry people. Each slate rests on the batten at its head and on the course below, and the middle of the slate is largely unsupported. Rain and wind press evenly across it, which it takes comfortably. A heel presses on one point, and the slate can snap along the line between its supports.
The worst part is that the break is hidden. The cracked slate often stays in place, so nothing looks wrong. The first sign is a damp patch weeks later, when rain finds the break and runs down onto the underlay. Our page on cracked slate covers what happens next.
Older slates are more brittle than new ones, and thin or already weathered slates break more easily. A tradesman who strolls across the roof to look at a chimney can do more damage in a minute than a winter of storms.
Slippery, steep and exposed
Breakage is the lesser risk. Slate has a smooth, hard face, and a film of moisture, a coat of moss or a dusting of frost turns it into a very slippery surface. A steep pitch makes this worse, and few slate roofs are shallow. A slide from the slope can end at the gutter, which is no barrier, or at the ground.
Wind adds to the danger on a coastal roof, where gusts can unbalance a person standing high above the ground. Roofing is work at height, and the tools for it, such as edge protection and roof ladders, exist because the risk is real.
Homeowners are often tempted to pop up and clear a gutter or push back a slipped slate. We would rather you did not, and not only for the sake of the slates. A look from the lawn, using a phone camera zoomed in, tells you a good deal.
How roofers work on slate without breaking it
Roofers do not walk on the slates, they work off equipment that spreads the load. A roof ladder has a hook that bears on the ridge, and its length rests on the slope, so the person climbs the ladder and never steps on a slate. A crawling board spreads weight in the same way on a flatter slope.
For bigger jobs, scaffold gives a platform at the eaves, and often access along the slope. It protects the slates, the gutters and the people, and it lets the work be done properly, not rushed. Whether a job needs scaffold depends on the roof, the way in and the task, and where poles go on the footway or road, the scaffold contractor, not you, arranges the licence with the county council.
Even with a ladder, a roofer handles slates carefully, and lifts the course above before touching a broken one. Valleys and flashings need extra care, which is why our page on slate valleys notes where the weak points are.
What to do if you have to get onto the roof
If there is a reason to go up, such as a chimney sweep, an aerial engineer or a surveyor, ask them how they will do it and what they will use. A good tradesperson will tell you about a roof ladder or board. If they plan to walk the slope, ask them to stop and call a roofer instead.
Ask for a look at the roof afterwards. A short survey, with photographs, shows whether anything has cracked. The same slates also tell you something about age and condition, as our page on matching old slates explains when a repair is needed.
The best protection is to need access less often. The slate roofing hub explains how such a covering is kept in order. A slate roof that is kept clear, with gutters that run freely and moss controlled, needs fewer visits. Our guide to slate underlay and sarking explains the layer beneath, which sits underneath and catches water if a slate does crack.
Checking the damage from below
You can learn a lot without leaving the loft hatch. Look at the underside of the slope with a torch after rain, and note any dark patches on the underlay, wet batten ends or daylight. Check upstairs ceilings for stains, which often appear a short way from the source.
Take photographs from the ground at different times of day. Low sun along the roof shows slipped courses and uneven lines, which are harder to see in flat light. A slate that sits proud or crooked is a candidate for a closer look.
Our surveys are done from ladders and boards, with photographs of your roof taken as we go, and a written quote with one total arrives afterwards. Leaks and storm damage get priority, and a roof that is letting rain in is made safe before the lasting repair is planned.
Up or down: two further questions
Does a freshly laid slate roof take more weight?
New slate is no more able to carry a boot than old slate, though it may be less brittle. The roof still depends on the battens and the overlap, and a crack in new slate leaks just the same, so access gear is still used.
Can I clear moss from slate myself?
Doing it from the ground, with a long soft brush, is far safer than climbing up. Scraping or pressure washing can damage slates and push water under the laps, so we would leave cleaning to a roofer who can reach the roof safely.
Tell us about your roof
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