How Long Does a Flat Roof Last?

Most flat roofs on houses wear one of three coverings. Torch-on felt is built from bitumen-soaked sheets that are melted together with a gas torch. GRP stands for glass-reinforced plastic: liquid resin and glass fibre that set hard on the deck, which people often call fibreglass. EPDM is a synthetic rubber sheet, normally glued down. Each has its own published life.

What are the typical figures?

Less, in its flat roof cost page updated on 26 October 2026, gives felt 10 to 20 years and GRP 25 to 40 years. Its warning for felt is that workmanship decides the outcome, with poor jobs failing inside 10 years. For EPDM, GreenSpec states an expected service life of 20 to 30 years, but Less gives 30 to 50. The two sources disagree, so we show both.

Read each range as a spread of outcomes, not an average you are owed, and remember that the same covering can behave very differently on two roofs. A felt roof at the low end and an EPDM roof at the top end can be on the same street, built a year apart, simply because one was laid carefully and kept clear.

Lead and zinc are heavier, costlier materials, and they are used on flat roofs where the finish matters, such as bay roofs, dormer tops and some porches. Their lives are quoted in decades, not years.

What do the metal roofs achieve?

On lead flashing, MyJobQuote's wording is that it can last for over 80 years, which sets a floor rather than a limit. VM Zinc reports that the BRE Environmental Product Declaration for its zinc states 100 years. Both come from firms and guides with an interest in the material, so treat them as the published figure and not a guarantee for your roof.

The long lives depend on the detailing. Metal expands and contracts with temperature, so the joints, rolls and fixings have to allow movement or they fatigue. A well-laid lead roof can outlast the house around it, and a badly fixed one can split within a few years, which is why the person fixing it matters as much as the sheet. BS 6229, the code for flat roofs with flexible coverings, applies to membranes and not to lead, so metal roofs follow their own guidance.

Published ranges assume a roof that is laid to a proper fall and cleared when needed. Take away either and the numbers stop applying. A roof that has been ignored for a decade is not on the same curve as one that has been looked at every spring. Standing water ages every covering faster than rain that drains away, because it holds dirt, freezes in winter and gives weeds a foothold.

Which problems cost a roof the most years?

Ponding comes first, usually the result of falls that were too shallow or a deck that has dipped. Blocked outlets come next, then damage from foot traffic, ladders and dropped tools. Detailing at edges, upstands and penetrations is the other regular culprit, since the sheet is thinnest and most stressed there. Moisture trapped inside the build-up, from a leak or from condensation, damages the insulation and deck whatever the covering says.

Underneath all of those is upkeep. A look in spring and autumn, a clear outlet and a quick patch while a fault is small are the least costly ways to add years. Our answer on flat roof maintenance lists the checks.

A roof announces its age before it fails outright. The signs are visible from a ladder or an upstairs window: felt that has gone brittle, splits or open laps, blisters, rubber that has pulled away from a wall, GRP with hairline cracks, and a patchwork of earlier repairs.

Is it worth repairing an old flat roof?

The answer lies in how the roof is ageing. A single fault on a roof in the middle of its range is an easy case for a repair. A roof right at the edge of its range, with several faults and signs of damp underneath, is where a run of patches ends up costing more than it saves, because each one hides a larger problem underneath.

The price of a replacement depends on the area, access, the covering and the condition of the deck and insulation beneath. As a guide to scale, MyJobQuote gives a typical UK range of £1,500 to £6,000 for flat roof construction (MyJobQuote, Oct 2026).

Our post on when to repair or replace an ageing flat roof goes further, and the flat roofing page lists what we take on. If yours is getting on, arrange a survey and the pictures will show where it stands.