The short answer
Not much, but it needs to be regular. A flat roof sheds water slowly, so the routine is short and sensible: keep the outlets and gutters clear, remove leaves and moss before they hold water, look over the edge trims and joints twice a year, and check again after a hard storm. Small jobs done early stop most of the repairs that would otherwise follow.
A flat roof forgives very little neglect, yet asks for very little time. A look in spring and another in autumn is a good rhythm.
Outlets, gutters and the debris that blocks them
Rain exits by an outlet, a gutter or a spout over the edge, and anything that narrows that route leaves the water standing on the surface. Leaves from a nearby tree, moss that drifts in from the neighbouring tiles and the grit that washes off a gravel layer are the usual culprits.
How often should the outlets be cleared?
Once the leaves are down in late autumn is the time that matters most, with a second look in spring. Lift out the debris by hand, wearing gloves, then pour a bucket of water down the outlet to see that it drains freely and does not back up. If you cannot reach the roof safely from a ladder, a roofer can do it.
Do not forget what lies downstream. A clear outlet feeding a choked downpipe still backs up. Brett Martin, a guttering manufacturer, suggests a fall of 1mm for every 600mm of gutter run, so a long run that has dipped in the middle keeps a puddle even when spotless, and the overflow lands on the wall below. The answer on why a flat roof outlet overflows follows the blockage step by step.
Trims, edges and joints worth a close look
The covering of a flat roof is usually the long-lived part. The weak points are the places where it stops: the drip trim at the edge, the joint against a wall, the collars round pipes and the seams between sheets or strips.
What does a roofer look for at the edges?
The metal or plastic trims that finish the roof edge can lift, crack or lose their sealant. Sections of membrane can pull away from an upstand, the short vertical return where the roof meets a wall. Lead flashings along a wall may have lifted. A bead of sealant that has hardened and split has stopped working.
Standing on a ladder, or leaning from an upper window, you can spot most of these without setting foot on the surface. Photograph anything that looks different from last time so that you can compare the two sets side by side. Our answer on flat roof trims and upstands goes through the details that most often open up.
Resist the urge to smear a tub of bitumen sealant over a joint. It rarely lasts, and it can hide the very cracks a roofer needs to see.
What to do after a storm
Wind lifts edges, and heavy rain exposes low spots, so a flat roof is worth a quick look after any serious blow. Start from inside, because a brown ring on the ceiling or a bubbled patch of paint is often the first sign that something has moved. Check the loft or room beneath before you go anywhere near the roof.
What should I check once the weather has passed?
Look for debris that has landed on the roof, for water that is still standing a day after the rain stopped, and for any trim, flashing or sheet that has shifted. A branch or a slate dropped from higher up can dent or puncture a membrane, so check the surface for cuts.
If anything is open and rain is forecast, a temporary cover or a quick patch is the sensible step before a permanent repair. Our order of work is to stop the water coming in, then plan the lasting fix once the roof is dry.
Keep dated photographs of any damage in case it needs to go to an insurer. Our answer on patch repairs on a flat roof explains when a patch will do and when it will not.
When upkeep stops being enough
Maintenance keeps a sound roof sound. It cannot rescue one that has reached the end of its covering's life, and it cannot cure a build that never drained properly in the first place.
How do I know when to stop patching?
Patches that keep needing to be redone, water that regularly pools for days, blisters or splits across the membrane and damp insulation under it all say the roof wants more than a clean. Published lives for flat coverings run from 10 to 20 years for torch-on felt (Less, Oct 2026) up to 25 to 40 years for GRP, a glass-fibre and resin finish, so a covering well inside its range may only need tending.
A short walk round the roof with a roofer is the clearest way to tell. We look at the whole roof, share pictures of any weak points, and separate what is repair from what is replacement, so the choice is yours to make with the evidence in front of you. The flat roofing page lists what we can take on, from a single repair to a full re-cover.
More on keeping a flat roof sound
Is it safe to walk on my flat roof to clean it?
Only if the roof is designed for it. Many membranes and decks are not made for foot traffic, and a slip or a puncture can cost more than the clean. Use a ladder to look, and a long brush from the edge where you can. If someone must go up, a roofer's access kit is the safer route.
Does a flat roof need re-coating or sealing regularly?
Not as a rule. Some coverings carry a manufacturer's own advice about topcoats or reflective finishes, so check what was fitted before applying anything. Adding a coating over a damp or flaking surface traps the problem. A survey identifies what you have, and whether it needs a treatment or just a tidy.
The full picture: Flat roofing in Taunton ยท More short answers