Most flat roof failures are detailing failures, not material failures. Upstands, outlets and junctions are where water gets in, so the right question is rarely just which material, but which material with which detailing, laid on what deck.
EPDM rubber
A single sheet membrane, usually laid in one piece on a domestic extension so there are no seams across the field of the roof. It stays flexible in cold weather, tolerates movement well and typically lasts 30 to 50 years. It suits extensions, garages, dormers and porches, and it is the system we specify most often on domestic work.
GRP fibreglass
A resin and matting system laid wet and cured in place, producing a hard seamless finish that takes foot traffic well. It suits balconies and roofs that will be walked on. It is less tolerant of structural movement than rubber, so the deck has to be right, and it needs dry conditions to lay properly.
Built up felt
Modern torch on felt is a considerable improvement on the material that gave flat roofs their reputation. Laid in layers with proper laps and upstands it performs well and remains cost effective on larger commercial areas. Expect a shorter service life than rubber on a domestic roof.
What matters more than the material
- Falls: water must run to the outlet, and a roof laid dead flat will pond
- Upstands: a minimum of 150mm at abutments, properly terminated
- Outlets sized for the area they drain, not simply reused because they were there before
- A sound deck, replaced where it is soft rather than covered over
- Ventilation on a cold deck construction, or condensation will do the job of a leak
Flat roof leaking or ponding? We will inspect the deck and the detailing, not just the surface. Call 01296 325155 or request a survey.
