Flat Roof Repairs in Brighton & Hove: A Guide

For most Brighton and Hove flat roofs, high-performance torch-on felt is the best-value choice on dormers and rear extensions, EPDM rubber suits simple rectangular roofs where a single seamless sheet will cover the whole area, and GRP fibreglass is the right answer for balconies and walked-on surfaces. Almost all flat roof failures here are caused by poor detailing at the edges rather than by the covering material itself — which is why a targeted repair often outperforms a full replacement.

Nearly every Brighton terrace has a flat roof somewhere: a rear kitchen extension, a dormer loft conversion, a bay top, a porch or a garage. They are also the single most common source of leaks we are called to across Hove, Brighton and Portslade.

Why flat roofs fail in Brighton

Rarely the material — usually the detail. Failed upstands where the flat meets brickwork, undersized or gull-blocked outlets, ponding caused by inadequate falls, perished mortar fillets instead of proper cover flashing, and old mineral felt that has gone brittle after twenty Sussex summers of UV.

Coastal exposure adds its own contribution: wind uplift at the perimeter on exposed Hove and Portslade properties, and salt corrosion of any metal trim or fixing. Gull nesting material blocking a single outlet can turn a well-built flat roof into a paddling pool within one spring.

The three systems worth using

• Torch-on felt (high-performance SBS, two or three layer): proven, repairable, excellent value on dormers and extensions — 20 to 25 year life when detailed properly. Needs a competent installer and hot works safety.
• EPDM rubber: a single sheet with no field joints on most domestic sizes, very good on simple rectangles, 30+ year potential life. Less forgiving around complex upstands and penetrations.
• GRP fibreglass: seamless, hard-wearing and walkable, ideal for balconies and terraces, 25+ years. Requires genuinely dry weather and a sound deck to install correctly.

What to avoid: single-layer pour-and-roll felt, liquid coatings applied over a wet or failing substrate, and any system installed without upgrading the falls when ponding was the original problem.

Repair or replace?

If the deck is sound and the failure is confined to one detail — a split upstand, a failed outlet, a lifted perimeter — a targeted repair is honest and cost-effective, typically £250 to £700. If the deck feels soft underfoot, the covering is blistered across the field, or moisture has spread beneath an apparently intact surface, patching just buys you a winter. A full replacement on a typical Brighton rear extension of 15 to 20 square metres generally falls between £2,000 and £4,000 depending on the system, deck condition and access.

A drone survey plus a thermal moisture check tells you which situation you are in before you commit. Thermal imaging is particularly valuable here because saturated insulation beneath a sound-looking covering is invisible any other way.

Dormer loft conversions

Brighton's loft conversion boom left a lot of dormer roofs with rushed detailing around cheeks, abutments and the junction with the main pitch. These are very repairable — but only if the upstand heights and terminations are put right rather than simply re-covered. Recovering over a bad detail reproduces the leak in eighteen months.

Minimum upstand height should be 150mm above the finished surface, with a proper cover flashing chased into the brickwork rather than a mortar fillet. If your dormer does not have that, you now know why it leaks.

Falls, outlets and the boring things that matter

• A flat roof should never be flat — aim for a minimum 1:80 fall to the outlet
• Fit leaf and gull guards to every outlet, and clear them twice a year in Brighton
• Two outlets are better than one wherever the layout allows
• Check the perimeter trim after every storm on exposed coastal properties
• Never let a new covering sit on a wet deck — the moisture has to come out first