The short answer
Check your flat roof in autumn and again in spring, and after any storm. Clear leaves and silt from the surface, gutters and outlets, look for splits, blisters, lifted edges and loose trims, and make sure water is draining away. Small defects sealed early cost little, while the same defect left through a wet winter can soak the deck.
A simple routine for two checks a year
You do not need specialist kit. A ladder that is safely footed, a torch for the underside, a brush and a bucket cover most of it. If you cannot reach the roof edge safely, do not stretch for it. Looking from an upstairs window, from a ladder at the eaves, or with a camera on an extending pole is enough to spot the obvious.
Autumn is the first check, once the leaves have fallen. Spring is the second, when the winter has shown you what moved. Add a quick look after any named storm or heavy fall of snow.
Each time, walk through the same list: the surface, the edges, the outlets, the junctions with walls and the ceiling below. A small notebook or dated phone photographs let you compare year on year, and they are useful if a roof ever has to be inspected for an insurance claim.
Staying off the roof is the safer habit. Most coverings can be damaged by foot traffic, and even a low extension is high enough to hurt you in a fall.
Clearing the surface, gutters and outlets
Leaves, moss, silt and windblown seeds collect in the low spots of a flat roof. Left alone, they hold moisture against the covering, grow moss and block the outlet, so the water that should run off stands on the surface instead.
Clear the roof with a soft brush or a gloved hand. Avoid a wire brush, a scraper or a pressure washer, which can damage the membrane or the mineral finish on felt. MyBuilder's cleaning guide cautions against pressure washing delicate coverings, and the thin skin of a flat roof is no exception.
The outlet is the key point. That is the hole or gutter where the roof drains. A box gutter, a lined trough running along a parapet wall or down between two slopes, is easily choked, and an overflowing one often shows itself first as a stain on the ceiling inside. Open the gutter ends, lift out the debris and run a little water to check the flow.
If moss has taken hold on a covering, remove it gently by hand and ask us before using any chemical wash, since some products do not suit every material.
What to look for on the surface
When the roof is clear, look closely. Each covering shows its age differently.
- Felt: cracks and crazing, blisters that have burst, bare patches where the mineral finish has worn off, and laps that have opened.
- EPDM: creases that hold water, a lifting edge, and pinholes or tears near the corners where the sheet is under most stress.
- GRP: hairline cracks, usually along a deck joint or at an edge, and crazing of the top coat.
- Lead: cracked seams, lifted flashings and white powdery corrosion on the surface.
A blister is not always urgent. A small, sound one can be left under watch, while one that is open or growing needs attention. Anything that looks like a split is worth a closer look, because water travels under a membrane and can emerge a long way from the damage.
Take a photograph of anything you are unsure about and send it to us on WhatsApp. It saves a visit if the answer is plain.
Edges, trims and the junctions with walls
The surface is rarely where a flat roof gives up. The details at its edges do. Check the drip trim at the fall edge, the fascia beneath it, and any aluminium or uPVC edging for movement and gaps. A trim that has dropped away from the deck lets wind-driven rain behind the covering.
At a house wall the covering rises as an upstand against the masonry, and a flashing, in lead or another metal, laps over its top edge to shed water. Look for lifted lead, a gap in the pointing above it, or sealant that has cracked and shrunk. Lead flashings are normally dressed into a mortar joint and held with wedges, so loose pointing near them is worth fixing too.
Look at rooflights and vents in the same way. Each is a hole through the covering, and every hole is a place to check the seal. Many leaks that seem to come from the middle of a roof turn out to start at one of these details. Our page on why a flat roof leaks lists the usual entry points.
Inside the building and after bad weather
The ceiling underneath tells you what the roof cannot. Look for new stains, a tide mark that grows after rain, peeling paint, a musty smell or mould near the edges of the room. A stain that appears only after rain points to a leak, while one that appears in cold weather and dries out can point to condensation, which is moisture from the room condensing inside the roof build-up.
After heavy rain, look at the roof again once the rain stops. Water that is still standing a day or two later suggests a fall problem, and our guide to ponding sets out what is normal and what is not. After snow, let it melt away naturally rather than chipping it off, since scraping can cut the covering.
Gutters are worth checking after a storm for another reason. A bent bracket or dislodged downpipe can send water back across a trim.
When to call us and what to expect
A routine like this tells you early. If you find a split, a lifted flashing, a blocked outlet you cannot clear or damp inside, ask a roofer to look. Repair is our first thought where it will hold, and a small patch or reseal is often all a young roof needs. If faults keep coming back, the rules for choosing between repair or replace are set out on their own page.
Maintenance helps, but it does not stop a covering reaching the end of its life. Typical lives depend on the material, as covered in how long a flat roof lasts, and on exposure and workmanship. For the wider picture, the flat roofing service page covers how we work, and the usual first step is a free survey, with photographs.
