If your flat roof needs replacing, our flat roofing service covers all the material options below, and you'll likely be quoted for two or three different choices. EPDM (rubber), GRP (fibreglass), and traditional felt are all widely used on residential flat roofs in the UK, and each has genuine advantages and trade-offs. This guide explains what each system involves, how they compare on durability and cost, and when each option is the better choice.
Traditional Felt (Torch-On)
Torch-on felt — layers of bitumen-modified felt bonded to the deck with a propane torch — is the most established flat roofing system in the UK. A three-layer torch-on system laid on a properly prepared deck will typically perform for 15 to 25 years, though quality of installation varies considerably. The primary limitations are its susceptibility to UV degradation over time, the fact that it becomes brittle in cold weather, and the requirement for torch access which rules it out where fire risk around the deck or surrounding structure is a concern.
EPDM (Rubber Roofing)
EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber membrane that has become increasingly popular on domestic flat roofs over the past 15 years. It is installed as a single sheet bonded directly to the deck, which eliminates the lap joints that are a common point of failure in felt systems. EPDM is extremely flexible and remains so across a wide temperature range — it does not become brittle in cold winters or lose its form in summer heat. It is also UV-stable and genuinely long-lived: a correctly installed EPDM system is rated to last 50 years or more.
- ✓No open flame required during installation — significantly reduces fire risk.
- ✓Single-piece installation means no laps in the middle of the roof slope.
- ✓Very lightweight — typically less than 1.5kg/m².
- ✓Can be installed over an existing deck without full strip-off in some situations.
- ✓More flexible over uneven decks than GRP.
GRP (Fibreglass)
GRP (Glass Reinforced Polyester) is a cold-applied system where fibreglass matting is laminated with resin and finished with a pigmented topcoat. Once cured, it forms a rigid, fully seamless surface. GRP is extremely hard-wearing, resistant to foot traffic, and is particularly well-suited to flat roofs that are regularly accessed, have complex detailing, or need to integrate with upstands, gutters, and penetrations in a very clean finish. It is also excellent for flat roofs that run directly into parapet walls or need lead-free detailing at abutments.
- ✓Fully seamless — no laps, no joints, no potential failure points.
- ✓Very hard surface — highly resistant to foot traffic and minor impact.
- ✓Excellent detailing capability around rooflights, outlets, and upstands.
- ✓Available in a range of colours as standard.
- ✓Requires a rigid, fully stable deck — not suitable over a deck that has any flex.
Which System Should You Choose?
For most domestic flat roofs — rear extensions, bay window returns, garage roofs — EPDM and GRP are both significantly better long-term investments than felt replacement. Between the two, GRP tends to suit roofs with complex detailing or where a hard, trafficable surface is required. EPDM tends to suit simpler roof shapes, situations where the deck has a degree of flex, and where budget is a consideration.
We will always specify the system that is best suited to your specific roof rather than the one that is easiest for us to install. We provide written quotations for each option where appropriate so you can see the full cost comparison before deciding.