What does a commercial roof survey cover?

The survey starts with the surface that keeps the rain out. On a single-ply or felt roof, that means checking seams and laps for lifting or splits, looking for blisters and cracking, and noting any patches from earlier repairs. On a profiled metal roof, it means the sheet laps, the fixings, the cut edges and the condition of the coating or paint. On a pitched roof of tiles or slates, it means slipped, cracked and missing units, the ridge and the verges.

Walking the roof is only part of it. Standing water, tide marks and dirt trails show where the roof is not draining, and a surveyor reads them like a map. The same marks, photographed from several positions, tell the owner where the water is going and why a patch did not hold last winter.

If the roof is fragile, the survey is done from safe access with the right equipment, never by stepping on sheets that could give way, and the report flags those areas so later visitors know to avoid them.

More commercial roof problems begin at the drainage than in the middle of the roof. A surveyor traces where water leaves the surface: the outlets, the rainwater pipes, the box gutters, the parapet gutters and the downpipes at the bottom. Each is checked for blockage, damage, movement and the way the roof is laid to meet it.

Falls matter here, and a surveyor checks them with a level or by watching where water travels. BS 6229:2025 keeps a minimum finished fall of 1:80 for flat roofs, and water still lying on the surface days after rain suggests the fall is not being achieved, or that the structure has dipped. Our answer on ponding on commercial flat roofs explains what that means for the covering.

Overflows, scuppers and the capacity of gutters get a look too, because a roof that drains well on a dry day can still flood in a downpour if the outlets are undersized or silted up.

The details are where leaks hide. The survey follows every edge, every wall upstand and parapet, every flashing and every opening cut through the roof for pipes, flues, plant, cables and fans. Each junction is checked for sealant failure, lifted terminations, movement and any place where the covering has drawn back from the masonry.

Rooflights get their own inspection: the glazing or sheets, the kerbs, the seals and, on older buildings, the fragility of the panel. Failed rooflights are among the most dangerous items on an industrial roof because people step on them without knowing.

Edges and access routes are noted as well, including any edge protection, walkways and safe routes for plant engineers, since a survey that finds the roof also finds the hazards for the next person who has to go up. Our guide to fragile roof safety in the same section sets out the principles.

A survey from above is incomplete. Inside, the attention moves to the underside of the deck or sheets, the soffit of a warehouse roof, ceilings in offices and shops, and any insulation within reach. Stains, rust runs, daylight through laps, damp insulation and mould show where water has been getting in, and they often point to a leak that is nowhere near its source.

Condensation is checked too. Water dripping from a roof is not always a leak, and a building that sweats in cold weather needs a different fix. See our answer on warehouse roof condensation for how the two are told apart.

Where a leak cannot be traced by eye, the next step is a dedicated leak search, covered in our guide to commercial roof leak detection. Tell the surveyor where and when you have seen water, because dates and locations narrow the search a great deal, and mention any recent work on the roof or on plant fixed to it.

A survey is only useful if it is written down. You should get photographs of each defect with a note of where it is, a description of the roof's overall condition, and a clear recommendation, either mend it, hold it together for the time being or replace it, with reasons given. A good report names the cause, not only the symptom, so you know whether the same fault will return.

After that comes the price. The quote is written, with one total, and what moves it is the area, the access, the new covering and any damage found beneath the surface. If a roof needs a different answer in different areas, the report says so.

Keep the report. It supports a landlord's or lender's questions, helps with an insurance claim, and gives a record for the next survey to compare with. Our commercial roofing team surveys shops, units, halls and blocks across the area, and the first visit starts with your account of the problem.