There are three flat roofing systems most homeowners will be quoted for. Here's how they really compare on cost, lifespan and reliability.
The three systems explained
When you ask for a flat roof quote, you'll usually be offered one of three systems: EPDM rubber, torch-on felt, or GRP fibreglass. Each has its place — and each has roofers who'll insist their preferred system is the only one worth fitting.
Below is the honest version, based on what we actually see fail (and last) on Oxfordshire properties.
EPDM is a synthetic rubber membrane, usually fitted as a single sheet for the whole roof. No seams across the field of the roof means no obvious failure points. Properly installed, it comfortably lasts 25–30 years and often more.
Pros: long lifespan, single-piece membrane, flexible (handles building movement), low maintenance. Cons: needs careful detail work at upstands and outlets, slightly more expensive than basic felt.
Modern reinforced bitumen membranes (often called 'torch-on felt') are a big step up from the old pour-and-roll felt of the 70s. A three-layer system can give 15–20 years of solid service.
Pros: well-understood, widely available, lower upfront cost. Cons: shorter lifespan than EPDM, multiple layers and seams, hot works on site, more prone to surface damage from foot traffic.
GRP (glass-reinforced polyester) is laid wet in resin and cures to a hard, seamless finish. It looks neat, takes foot traffic well and lasts 20–30 years.
Pros: hard-wearing, smart finish, good for balconies and walkways. Cons: rigid (can crack with significant building movement), needs dry conditions to install, more expensive than felt.
For most domestic flat roofs — extensions, garages, porches — we recommend EPDM rubber. It's reliable, has the longest practical lifespan, and is the lowest-fuss system to live with.
For balconies and roofs that get walked on regularly, GRP is often a better fit. For tight budgets or short-term ownership, a quality torch-on felt system is still a sensible option.
Why installation matters more than the material
We see more failed flat roofs caused by bad installation than by the wrong choice of material. Poor falls, badly detailed upstands, missing trims, undersized outlets — these are what cause leaks, regardless of whether the membrane is rubber, felt or GRP.
If you're getting flat roofing quotes, ask the roofer to walk you through the falls, the outlets and the edge details — not just the membrane.
We install all three systems across Witney, Oxford, Carterton and the wider Oxfordshire area. We'll recommend what suits your property, not what's easiest for us to fit. See our flat roofing service for more.
Is EPDM really better than felt?
For long-term value, yes — a single-ply EPDM roof typically outlasts a felt roof by 10+ years and has fewer failure points. Felt is still fine for budget-driven projects.
Can flat roofs be insulated?
Yes. Warm-deck construction with PIR insulation board under the membrane is now standard for new flat roofs and meets current Building Regs.
How much does a new flat roof cost?
As a rough guide, a small garage flat roof in EPDM is typically £1,500–£3,000, while a large extension can be £4,000–£8,000+ depending on size, insulation and access.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.