What a new flat roof costs in Brighton in 2026 — GRP fibreglass, EPDM rubber and felt compared on price and coastal lifespan, with honest guidance on which membrane suits your property. Free survey across Brighton and East Sussex.
A flat roof in Brighton typically costs £70–£90 per square metre for GRP fibreglass, £55–£75 for EPDM rubber, and less for felt. A standard 25m² extension runs £1,400–£2,250 in GRP. GRP lasts longest in Brighton's coastal conditions, making it the best value over time.
A single seamless membrane with no joints to fail. GRP costs £70–£90 per m² installed and lasts 30–40 years in Brighton's coastal conditions. It's our default recommendation for the city's exposed, south-facing extensions.
A rubber membrane laid in sheets with bonded laps. EPDM costs £55–£75 per m² and suits sheltered inland positions. In coastal Brighton, the lap joints are the weak point, giving 20–25 years versus GRP's 30–40.
Traditional built-up felt is the cheapest option but has the shortest life — 8–12 years in Brighton's coastal UV and salt. We rarely recommend it for replacement where longevity matters, though it still appears on new-build and budget work.
Whatever the membrane, a sound deck matters more than the covering. We strip to the deck, address any rot or saturation, and detail all upstands, outlets and trims correctly — the details are where flat roofs actually fail.
Brighton and Hove have an enormous stock of Victorian and Edwardian properties with rear kitchen extensions — Poets Corner, Hanover, the Hove Avenues, Preston Park. The vast majority of these extensions have flat roofs, and most were built or last covered in the 1960s–80s. That means thousands of flat roofs across the city are now 40–60 years old and at or past the end of their life. The scale of this market is why flat roofing is one of our most-requested services.
Brighton's grid layout means many rear extensions face close to due south — maximum UV and thermal cycling. A dark felt surface on a south-facing Poets Corner extension can reach 75–85°C in summer sun against cool Channel air, and that daily cycling is what fatigues felt and EPDM lap joints. GRP's seamless rigid membrane handles this cycling better, which is why we specify it for exposed Brighton positions despite the higher upfront cost.
Within a kilometre of the seafront — much of central Brighton, Kemp Town and Hove — salt air shortens every membrane's life. This is where GRP's advantage is greatest: no lap joints means no adhesive for salt and thermal movement to attack. Sheltered inland positions in Haywards Heath or inland Burgess Hill can justify EPDM, but the closer to the sea, the stronger the case for GRP.
A typical 25m² rear kitchen extension on Shakespeare Street in Poets Corner, Hove, with failed 1970s felt. Stripping to the deck, replacing a section of saturated OSB, and installing a new GRP membrane with all upstands and a new outlet costs £1,600–£2,400 in 2026. The same roof in EPDM would be £1,375–£1,875 — cheaper now, but likely needing replacement 10–15 years sooner in this south-facing coastal position.
One factor that affects flat roof cost in Brighton is insulation. When you replace more than half of a flat roof, Building Regulations generally require the thermal performance to be upgraded to current standards — a “warm roof” build-up with insulation above the deck. On Brighton's older extensions, originally built with little or no insulation, this adds cost but transforms the comfort and energy performance of the room below, which matters on the south-facing rooms that overheat and the north-facing ones that run cold. We factor the regulations into every flat-roof quote, because a replacement that ignores them isn't compliant, and a warm-roof upgrade on a habitable Brighton extension is usually money well spent. We explain the build-up options and their cost implications at survey so you can make an informed choice rather than discovering the requirement mid-job.
| GRP fibreglass (supply & fit) | £70 – £90 / m² |
| EPDM rubber (supply & fit) | £55 – £75 / m² |
| Torch-on felt (supply & fit) | £45 – £65 / m² |
| Standard 25m² extension, GRP | £1,400 – £2,250 |
| Standard 25m² extension, EPDM | £1,200 – £1,875 |
| Garage roof, GRP | £900 – £1,600 |
| Deck repair (per section) | £150 – £400 |
| New outlet / detailing | £80 – £200 |
Indicative Brighton pricing. Every quote follows a free survey. Prices include VAT where applicable.
Key fact: The Single Ply Roofing Association identifies lap-joint adhesive failure as the principal long-term weakness of sheet membrane flat roofs — a vulnerability that seamless GRP avoids entirely, and one accelerated by the thermal cycling of Brighton's Channel-facing position.
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“Replaced the old felt on our kitchen extension with GRP. They stripped it back, found rotten decking we didn't know about, showed us, and sorted it. Seamless finish and a proper guarantee.”
“GRP flat roof on the rear extension. Explained clearly why GRP over EPDM for our south-facing roof. Tidy work, fair price, and no lap joints to worry about.”
“Our garage flat roof was leaking for years. GRP membrane, done in a day, spotless. Cheaper than I feared and the 30-year outlook makes the felt we kept patching look like false economy.”
A flat roof in Brighton costs £70–£90 per m² for GRP fibreglass, £55–£75 for EPDM rubber and £45–£65 for felt in 2026. A standard 25m² extension runs £1,400–£2,250 in GRP. Deck repairs and detailing can add to the total.
GRP is better for most Brighton properties. Its seamless single membrane has no lap joints to fail in coastal salt air and thermal cycling, lasting 30–40 years. EPDM is cheaper and fine for sheltered inland positions, but its lap joints are the weak point in exposed, south-facing coastal locations.
In Brighton's coastal conditions, GRP fibreglass lasts 30–40 years, EPDM rubber 20–25 years, and felt just 8–12 years. Salt air, coastal UV and thermal cycling from the Channel shorten every membrane's life compared to inland, which is why seamless GRP is the most durable local choice.
Brighton and Hove have vast Victorian and Edwardian stock with rear kitchen extensions, almost all flat-roofed. Most were built or last covered in the 1960s–80s, so thousands are now 40–60 years old and at end of life — which is why flat roof replacement is one of the most common jobs across the city.
Small, isolated damage on an otherwise sound membrane can be repaired. But once felt is widely cracked, blistered or the deck beneath is saturated, replacement is the sensible spend. We assess the deck and membrane at survey and give honest advice rather than patching a roof that's past saving.
Only where needed. We strip to the deck and inspect it — on Brighton's older extensions we often find sections of saturated or rotten OSB, particularly where felt has been leaking for years. We document and quote any deck repair before proceeding, never hiding it in the total.
Replacing a flat roof like-for-like is normally permitted development. Changing a flat roof to pitched, or altering the roofline, usually needs planning permission. Listed buildings and some conservation areas have additional constraints. We advise on this during the free survey.
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