Flat roofs in EPDM, GRP and felt

The system has to suit the deck

EPDM rubber, GRP fibreglass and built-up or single-ply felt each have strengths. EPDM is often a good, flexible covering on a well-prepared deck. GRP can give a hard, joint-light finish on regular shapes, provided the weather and the substrate play along during install. Modern felt systems still have a place, especially on simpler garage and outbuilding roofs, but an old, brittle mineral felt that is already splitting is rarely worth another patch. The deck, falls, insulation and abutments decide more than a brand name does.

Falls, outlets and ponding

A “flat” roof still needs a fall to an outlet or a drip. Standing water is one of the most common reasons a covering ages early. If the deck has sagged or the outlet is poorly placed, simply sticking a new membrane over the same puddle will not fix it. We look at drainage as part of the survey, including internal outlets, hoppers and the way an extension roof meets the main house wall.

Edges, abutments and rooflights

Most flat-roof leaks start at the details: a thin upstand against a wall, a poorly dressed kerb around a rooflight, a trim that has come away in the wind, or a junction with a pitched roof above. Those details are written into the quote. If a conservatory, garage or dormer cheek needs work as well as the main deck, that is scoped rather than assumed.

Repair or replace

A local puncture or a failed trim on an otherwise sound, relatively recent covering can often be repaired. A felt roof that is cracked across the bays, or a covering that has already been overlaid more than once, is usually a replacement conversation. We would rather say which it is than sell a short overlay that traps problems underneath.