How long does a flat roof last?

MyBuilder's 2026 flat roof cost guide puts flat roofs generally at between 15 and 30 years. That is a useful starting band, but it blends very different coverings together. The table below separates them. The figures come from different publishers using different methods, so read each row as a rough range rather than a measurement.

The spread inside a row is real. Less puts it plainly: felt laid well might reach 20 years, while a poor job could fail in under ten. The gap between the best and worst felt roof is bigger than the gap between an average felt roof and an average EPDM one, so who lays the roof and how matters as much as what goes on it.

On paper, lead sits at the top. Sheet lead on a flat roof is quoted at 50 to 100 years, but it is also the dearest option: MyBuilder's flat roof guide gives lead at £150 to £200 or more per m², against £70 to £100 for bitumen felt, £90 to £130 for EPDM and £95 to £150 for GRP. Lead also suits a small area such as a porch or bay better than a whole extension.

Among the coverings most householders actually compare, EPDM and GRP trade places depending on which source you read. The cost guides we looked at put GRP at 25 to 40 years and EPDM at 20 to 30 years or more, while one trade body quotes 50 years or more for a well kept EPDM roof. Felt generally sits lowest on the range, though it also has the lowest price per m².

If you are weighing two systems directly, our guide to choosing a flat roof material covers the trade-offs beyond lifespan, and a roofer should be able to explain how the figures apply to your own roof, not just to the product in general.

Ponding is the usual starting point. A flat roof is meant to fall gently towards an outlet: the code of practice behind BS 6229 recommends designing for a fall of 1:40, so the finished roof still achieves at least 1:80 after tolerances and deflection. Where the deck sags or the falls were never right, water sits on the membrane, and standing water ages every covering faster.

Poor detailing comes next. Upstands, edge trims, outlets and the joints around rooflights are where a membrane is most stressed or cut, so we look closely at whether those junctions were finished neatly. Trapped moisture is the other common cause. If the deck was damp when the covering went on, or warm moist air from the house condenses inside the build-up, blisters and soft spots follow.

Foot traffic and debris

Regular walking on a membrane never meant to be walked on, leaves blocking outlets and overhanging branches all add wear. None of them looks dramatic in a single season, but together they take years off a roof. A sheltered roof under a tree can quietly collect silt and moss in a corner, hold water against an upstand and age faster than the open stretch beside it.

A manufacturer's warranty on a flat roof system is a statement about the product, usually under defined conditions. It does not forecast how long your roof will last. One cost guide says manufacturer warranties of 20 to 25 years are standard for EPDM, yet the sources quote working lives well beyond that for a well kept roof, and a poorly laid one can fall short of its warranty period.

The same caution applies to our own paperwork. We give a 10-year workmanship guarantee in writing, and that covers how the roof was fitted, not the age the membrane may reach. Ask any roofer to separate the two, and be wary of anyone who quotes a warranty as though it were a service life.

When a roof reaches the end of its range, it rarely fails all at once. Small signs come first: a hairline split along a seam, a patch that stays damp after the rest has dried, a ceiling stain that comes back after being painted. Catching those early gives you time to plan a replacement on your own schedule, rather than reacting to a bucket under a drip in January.

Upkeep is cheap compared with replacement. Clear outlets and gutters of leaves and silt, keep moss and debris off the surface, and look the roof over after storms for lifted edges, split seams or cracking at upstands. Inside, check the ceiling beneath for new stains. Our page on the question of whether modern flat roofs leak explains where leaks tend to start, and the one on replacing a flat roof in winter covers timing if yours is nearing the end.

When a roof does need work, our survey records the deck, falls and covering in photographs, and the quote that comes after covers the whole job. Our flat roofing page sets out the systems and typical costs we work with.