EPDM vs GRP vs felt: which flat roof is best?

For most homes, EPDM rubber offers the best balance of long life (often 20–30+ years) and value, GRP fibreglass suits complex or walk-on roofs with its hard seamless finish, and felt is the lower-cost choice. The right pick depends on your roof — a free survey confirms it.

The three flat roof systems explained

If you are replacing a flat roof on an extension, garage, dormer or porch in Sunderland, you will usually be choosing between three coverings: EPDM rubber, GRP fibreglass, or felt. They do the same basic job — keep water out of a low-pitch roof — but they differ in how long they last, how they cope with our North East coastal weather, and what they cost to install.

• EPDM rubber — a single, flexible rubber membrane, usually laid in one piece with very few joints. Cold-applied, so no naked flame on the roof.
• GRP fibreglass — glass-reinforced plastic laid wet over a board deck and cured into one solid, seamless skin with a hard, walk-on finish.
• Felt — modern torch-on felt is built up in two or three bonded layers. A big step up from the old single-layer felt that gave the material its dated reputation.

EPDM vs GRP vs felt: how they compare

Lifespan and durability

All three can give you well over a decade of service when installed correctly on a sound, well-drained deck. EPDM tends to lead on longevity because a single rubber sheet has so few joints to fail, and the material stays flexible through hot summers and cold North East winters without cracking. GRP is extremely tough and resists foot traffic well, which makes it the go-to for balconies and roofs that get walked on, though it relies on a rigid, dry deck to avoid hairline cracking. Modern multi-layer felt is far better than its old reputation, but as a built-up system it generally has the shortest service life of the three.

Cost: what drives the price

Felt is usually the lowest upfront cost, EPDM sits in the middle, and GRP is often the highest because it is labour-intensive to lay and cure. But the covering itself is only part of the bill. The bigger cost drivers are the size and shape of the roof, the condition of the timber deck underneath (rotten boards must be replaced), access and scaffolding, and details like upstands, trims and outlets. For how flat roof prices fit alongside other work, see our roof cost guide. We never quote blind — every price follows a free inspection.

Which flat roof should you choose?

For a straightforward garage or extension roof where value and longevity matter most, EPDM is hard to beat. If the roof is complex in shape, will be walked on, or you want a hard, colour-matched finish for a balcony or dormer, GRP fibreglass is often the better fit. If budget is the priority or you are nearing the end of an existing felt roof’s life, a quality torch-on felt system is a sound, lower-cost option. There is no single “best” — the right answer depends on your roof, which is exactly what a survey is for. You can read more about our flat roof installation and repair service, and if you are weighing up patching versus a full re-cover, our repair or replace guide helps you decide.

What about repairs and leaks?

Whichever system you have, a flat roof that is leaking does not always need replacing — localised splits, failed upstands or blocked outlets can often be repaired. Our roof repair team can trace the real cause rather than just patching the symptom. If water is coming in right now, our 24/7 emergency roofers can make the roof safe the same day across Sunderland and the North East.

Get an honest recommendation

The best way to choose between EPDM, GRP and felt is to have your roof looked at in person. We will tell you which system genuinely suits your roof and budget, explain the trade-offs in plain English, and give you a fixed, no-obligation price. Call 07474 701968 (Mon–Sat 8am–6pm, plus 24/7 emergency) or request a free quote.