Last reviewed: 2026
Modern torch-on felt is cost-effective and repairable, GRP fibreglass gives a seamless rigid finish well suited to complex detailing, and EPDM rubber is a single flexible sheet that copes well with movement. The deck condition and the roof's shape usually decide between them.
Torch-on felt
Multi-layer torch-applied systems are the traditional choice and remain a good one. They are economical, straightforward to repair locally, and tolerant of imperfect decks. Expect a shorter design life than GRP or EPDM, and expect the detailing at upstands and outlets to be what determines how it performs.
GRP fibreglass
GRP is laid wet and cures into one seamless rigid layer with no joints to fail. It suits roofs with rooflights, upstands, kerbs and awkward junctions, and it takes foot traffic well. It needs a sound, dry, correctly boarded deck and dry weather to install, so it is more weather-dependent than the alternatives.
EPDM rubber
EPDM is a single sheet of synthetic rubber, usually installed in one piece on domestic-sized roofs. It stays flexible in cold weather, accommodates deck movement and installs without heat. Its performance depends on the bond and on well-formed corners and trims.
What actually decides it
The deck comes first. If it is wet, soft or poorly falling, no covering will last — that has to be corrected regardless of system. After that it is shape and use: complex detailing leans towards GRP, larger simple rectangles suit EPDM, and tight budgets with straightforward geometry are well served by felt.
Whichever is chosen, insulation, falls to the outlet and upstand heights matter more than the brand on the datasheet.