GRP fibreglass and EPDM rubber are the two modern flat-roofing systems that have largely replaced traditional felt. Both will comfortably outlast a torch-on felt roof. The right choice depends on the size and shape of the roof, whether it will be walked on, and your budget.
EPDM rubber roofing
EPDM is a synthetic rubber membrane, usually laid as a single sheet and bonded to the deck with adhesive.
- Lifespan: 20-30 years in practice, often longer.
- Cost: lower material and labour cost than GRP.
- Installation: fast, and it can be fitted in cooler or slightly damp conditions.
- Strengths: stays flexible in cold weather, copes well with a deck that moves or expands, very few seams on a simple roof.
- Weak points: the bonded seams and upstands at parapets and pipes are where failures happen if the install is rushed. Not designed for regular foot traffic. Finish is black only.
Best for: garage roofs, larger simple flat roofs, extensions with a straightforward rectangular roof, and jobs that need to be watertight quickly.
GRP fibreglass roofing
GRP (glass-reinforced polyester) is laid wet – layers of resin and glass matting that cure into a single seamless hard shell with a coloured topcoat.
- Lifespan: 25-30+ years.
- Cost: higher – more materials, more skilled labour, longer on site.
- Installation: needs dry weather and temperatures above about 5°C; a poor install in the wrong conditions is the main cause of early problems.
- Strengths: completely seamless, hard-wearing, you can walk on it, and it takes a range of topcoat colours and anti-slip finishes.
- Weak points: more rigid than rubber, so a deck that flexes significantly can cause hairline cracking over time. Repairs need a specialist.
Best for: balconies, roof terraces, dormer tops, bay window roofs, porches, and any flat roof that is on show or gets foot traffic.
Quick comparison
- Cheapest: EPDM
- Best for foot traffic and appearance: GRP
- Best for large simple roofs: EPDM
- Best for complex detailing and upstands: GRP (seamless) or a skilled EPDM install
- Fastest to fit: EPDM
Whichever system you choose, the deck, insulation, falls (so water drains) and edge detailing matter more than the membrane brand. A good flat roof is a good build, not just a good product.
Arkivon Group fits both GRP and EPDM flat roofs across North West London, alongside slate, tile and leadwork. See our roofing services or book a free roof inspection and we will recommend the right system for your roof and give you a fixed price.
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