Can You Walk on a Flat Roof?

The deck matters more than the covering

What you feel underfoot is the membrane, but what holds you up is the deck beneath it. Most domestic flat roofs are boarded with plywood, OSB (oriented strand board, made from compressed wood strands) or older chipboard laid over timber joists. Sound boards on sound joists will bear a person. Soft or rotten boards will not, and you cannot see rot from above. A roof that feels springy, or that dips where you step, has a deck that needs attention before anyone walks on it again.

Roofs that have ponded for years are the worst. Water sitting on a surface softens the boards from the top and leaves them weak, so a roof that looks fine can fail under a heel. Our article on ponding on a flat roof explains how that happens.

How each covering copes with foot traffic

GRP is a hard fibreglass laminate and is the most resistant to being walked on. A good topcoat and a sound deck will take regular light traffic, and it is the one covering often specified for roofs used as balconies. EPDM rubber is tough but soft. It tolerates the occasional step, but grit under a shoe can grind into the surface and a dropped tool can cut it. Walking on a rubber roof in studded boots is a bad idea.

Torch-on felt is the most vulnerable. Old felt becomes brittle, and the mineral chippings that protect it are knocked off by footsteps, leaving bare bitumen exposed to sunlight. A single heel can crack a cap sheet that is past its best. Where we lay felt on a roof that will need regular access, we suggest walkway pads or a protected route. Our comparison of EPDM, GRP and felt sets out their other differences.

Fragile rooflights and edges

The greatest danger is not damage to the roof. It is injury to the person. Rooflights and some older sheeting can break under a person's weight, and a fall through one is a serious accident. A rooflight that looks solid can be brittle with age, and moss or leaf litter can hide it altogether. If your flat roof has any glazing in it, treat it as fragile and keep off.

Edges are the other hazard. A flat roof on an extension or a dormer has an unguarded drop on at least one side, and the surface is slippery when wet or mossy. If a roof needs to be accessed often, for a satellite dish or solar panel cleaning, say, it should have proper edge protection and a defined walkway rather than relying on luck.

What to carry, and what to leave

Your own weight is only part of the load. A bag of tools, a ladder lifted on to the roof, a bucket of water or a bag of moss scrapings all concentrate load on a small patch. Sharp edges are worse than weight. A screwdriver dropped point-down, a stone caught in a boot tread or a ladder foot dragged across the surface can cut a covering that would have shrugged off a footstep. A kneeling board or a sheet of ply laid flat spreads the load, and a pair of clean, soft-soled shoes does less harm than work boots.

Hot work is a separate matter. Never use a blowtorch, a heat gun or a barbecue on or near a flat roof, and keep cigarettes and candles well away from felt and rubber. Bitumen and resin both burn. If a roof needs a gas torch, as with laying new felt, that is a job for people who know how to do it safely.

Safer ways to look at your roof

You can learn a lot without stepping onto it. Look from an upstairs window, photograph any pools, cracks or lifted seams, and check the gutter and outlet from a ladder placed on firm ground rather than from the roof itself. A pole camera or a drone survey can show detail without anyone climbing up.

When a roof needs inspection or work, our free survey includes photos of your own roof, so you can see the condition without risking a fall. We say where it is safe to walk and where it is not, and the quote that follows is fixed and in writing. If you plan to use the roof regularly, turning it into a balcony is a different specification from a plain weather roof, and the main flat roofing page lists the systems we fit.