Is GRP fibreglass better than EPDM?
Neither material is universally better. GRP forms a rigid seamless surface, while EPDM is flexible and suits many large uncomplicated areas. Roof movement, deck construction, detailing, appearance and installer experience should determine which system is more appropriate.
EPDM vs GRP vs Torch-On Felt: The Flat-Roof Comparison
Three systems cover almost every domestic flat roof: single-ply EPDM rubber, GRP fibreglass, and torch-on felt. The right pick depends on the deck, the detailing and how long the roof is expected to last.
EPDM rubber is a large sheet vulcanised on site with heat-welded or taped seams. Well-installed EPDM commonly performs for 25+ years, handles building movement, and detail work is straightforward.
GRP (glass-reinforced plastic) is laid up wet as a seamless membrane. Excellent walk-on strength and rooflight kerb detailing, but sensitive to deck movement and cold-day installation — GRP that cracks tends to crack repeatedly.
Torch-on felt is the traditional multi-layer bituminous system. Cost-effective and reliable when correctly installed; expect 15–20 years depending on grade. Watch for weld failure at laps as it ages.
For a new extension roof we usually recommend EPDM or GRP — the small extra cost buys another 5–10 years and better detail work. For a straight replacement over a sound deck, budget can steer the choice.
Whichever system, the failure point is almost always the detail: upstands, drips, penetrations and rooflight kerbs. Ask any quoting roofer to explain those details before you sign.