Can you walk on a flat roof?

There are two kinds of flat roof. One is a waterproof lid over a room or a garage, designed so that rain runs off it and nothing more. The other is a terrace or balcony, with a covering made to take foot traffic, usually with a protective finish, paving, decking or a firm surface laid over it. The first can be walked on briefly for inspection or clearing a gutter. The second is meant for regular use.

You can tell them apart from the way the roof is finished. A roof with a surface of slabs on supports, timber decking, or a thick textured topcoat was built for use. A roof with bare felt, a thin single-ply sheet or a glossy GRP finish was not. Pale scuffs on a dark surface, or a worn strip running across it, show where people have already been walking. If you are unsure, assume the second and ask a roofer before you step out of a window onto it. The answer affects your safety and the life of the covering, and it is worth settling before the first step.

Felt is soft in warm weather and can be scuffed, dented or torn by a heel or a dragged ladder foot. EPDM, a synthetic rubber sheet, is flexible and tolerates light traffic, but it can be cut by a sharp stone or tool. GRP is hard-wearing but can crack if the deck moves or if something heavy drops, as our answer on why GRP roofs crack explains.

Under the covering sit insulation and boards. On a warm roof, where the insulation is under the waterproof layer, repeated walking in one line can compress the insulation and leave a dip where water will stand. Standing water is a problem in its own right, and we cover it in standing water on a flat roof. A worn path across a roof is usually the first sign that someone has been using it as a shortcut.

Some flat or low roofs are fragile. Rooflights, glass or plastic domes, polycarbonate sheets and old fibre cement sheets can all break under weight, and the fall through them is serious. A rooflight set into a flat roof can be hidden by moss or a layer of dirt, so look for it before you go anywhere near the middle of the roof.

If there is any chance the roof is asbestos cement, which buildings from before 2000 can have, do not walk on it or break it. HSE guidance lists asbestos cement sheeting as always fragile, and the work to deal with it has rules of its own. Our page on flat roofing gives the wider picture, and when a roof looks fragile we assess it from a secure vantage point and photograph what is visible.

A ladder needs to be tied or footed and to reach well past the edge so you can step onto the roof without stretching. Wear shoes with a soft, clean sole and keep off the roof in wet, frost or wind, when the surface is slippery and a gust is risky. Never carry a heavy load up, and never go up alone, since nobody would know if you were hurt. Tell someone at home where you are, and come down if the weather turns while you are up there.

Keep clear of the edge. Many flat roofs have no guard rail, and the drop can be a storey or more. If the job is only clearing leaves from an outlet, a long-handled tool from a ladder may do the job without ever setting foot on the roof. If it needs more than that, the safer answer is a roofer who has the right equipment and does this every week.

If you want to use a flat roof as a terrace, or need to reach plant, an aerial or solar equipment, say so at the start. A roof that must take traffic should be designed for it from the beginning, with a suitable covering, protected walkways and a safe edge. Tell us who will use it and what will stand on it, whether people, planters or storage, because the deck and the structure have to be sized for the load. Adding a terrace afterwards means checking the structure, the falls and the covering, and it may bring Building Regulations and planning questions that we would explain before any work.

For maintenance access alone, walkway boards or tiles laid on a protective layer take the wear off the covering. Whichever covering the roof has, our page on flat roof lifespan shows how long it typically lasts when it is looked after, and the cost of a protected path is small beside a replacement covering.