The short answer
After winter, check four things: gutters and outlets for blockages, laps and fixings for movement, rooflights for cracks and standing water on flat areas. Do it from the ground, from inside the building and from a safe platform, never by walking on the roof. Asbestos cement sheets and old rooflights are fragile. Photograph whatever you find and ask a roofer to survey it.
Wind, rain and frost find the weak points in a commercial roof over the cold months. A methodical check in spring shows where they are before the next storm.
Start with the gutters and outlets
Gutters and outlets carry a whole roof's rainfall, so a blockage there causes damage far from the source. Leaves, moss, silt and debris collect in autumn and sit through the winter, and frost then swells whatever water is left standing in a joint. A cheap clear-out in spring is often the difference between a dry ceiling and a stained one.
What do you look for?
Look for overflow staining on the wall below, green or black streaks, gutters that sag or have pulled off their brackets, and joints that drip. On a flat roof with an internal or box gutter, check the outlets and any overflow for blockage. Our page on box gutter leaks explains why a choked outlet leads to a leak inside the building.
Gutters are best cleared from a tower or platform with edge protection, not from a ladder leant against the eaves of a fragile roof. The fall in a gutter matters for drainage as well. Manufacturer guidance from Brett Martin for rainwater gutters is 1mm of fall for every 600mm. A gutter that holds water along its length may have moved or sagged, and a roofer can check the line with a level.
Laps, fixings and sheet movement
Profiled sheets are fixed with screws or bolts through the profile and they overlap at the laps. Wind and winter temperature swings work these joints loose over time.
How do you spot a failing lap?
From inside, look for drips at the overlaps, daylight through joints and rust trails down the underside. From the ground, look along the eaves and ridge for lifted edges, missing caps and sheets that no longer sit in line. Flashings at walls and ridge pieces are checked in the same way.
Somerset Building Control lists loose roof tiles among its dangerous structure examples, and states that the owner of a building which turns dangerous bears the bill for making it safe. Anything that looks ready to drop onto a path, a yard or a neighbour's land is the first priority. Photograph it, cordon off the ground below, and call us: the roof is made safe first, with the proper repair following once the cause is clear. Fixings that rattle or lap edges that lift in the wind are early warnings of the same trouble.
Rooflights and ponding
Rooflights let daylight in, and they age faster than the roof surrounding them. Cracking, yellowing, crazed surfaces and loose fixings all show up on a post-winter look.
Are rooflights safe to lean on?
No. Treat every rooflight as fragile, including ones that look solid. The sheets either side deserve the same respect, and on an AC roof HSE guidance leaves no doubt that fragility is the rule. Nobody should walk across a roof to examine a rooflight, so use a platform alongside, a camera on a pole or a view from inside the building.
Ponding is standing water on a flat or low-pitched area, and it shows as a ring or tide mark where water sat. BS 6229:2025 keeps a 1:80 minimum finished fall for roofs under flexible waterproof coverings, so water that stays put points to a fall problem, a sagging deck or a blocked outlet. Continuous ponding wears membranes faster, and a repair that leaves the pond in place often fails again. Photograph the water at its deepest and the tide mark once it has dried, so a roofer can compare the two and see how far the pond spreads.
Safe access, records and next steps
The quickest accidents happen to people checking a roof for themselves. Fragile roofs give way without warning, and winter leaves algae and frost on edges and ladders.
What is the safe way to look?
Use binoculars or a camera from the ground, a view from inside, and a platform or tower for close detail. If the building dates from before 2000, assume the sheets could be asbestos cement until a survey says different, and read our answer on asbestos cement roofs.
Write down what you find with the date, and photograph it. Where a gale did the harm, ring the insurer ahead of permanent repairs, as set out in our answer on business insurance and roof leaks, and keep the receipts for any stopgap work. The wider service is on our commercial roofing page. Our survey brings your photos and a findings summary together, with one total price in writing to follow. Start with a photo of the worst area and where it sits on the building.
More on spring roof checks
How soon after a storm should a unit's roof be checked?
As soon as it is safe to look from the ground and from inside. Check for water coming in, lifted sheets and anything hanging loose. Do not wait for the spring if a storm has passed. Photograph what you see, make the building safe, and have a roofer survey the roof before the next spell of bad weather.
Is moss on a commercial roof a problem?
Moss keeps water against the surface and can choke gutters and outlets as it dies back. On profiled metal and fibre cement it is mainly a drainage and slip problem. Never scrub or jet wash a roof that might be asbestos cement, because that can release fibres. Ask a roofer to survey it and advise first.
The full picture: Commercial roofing in Taunton ยท More short answers