Flat Roof Systems Compared: EPDM vs GRP vs Felt
If you have a flat or low-pitched roof — extension, garage, dormer, balcony — you need to choose between three main systems. Each has real strengths and weaknesses.
EPDM Rubber
Single-ply synthetic rubber membrane. Seamless (no joints in the field), very flexible, 50+ year lifespan. The modern gold standard for most flat roofs.
Best for: Extensions, dormers, garage roofs, most residential flat roofs.
Lifespan: 50+ years. Manufacturer warranties of 20-25 years standard.
Cost: £75–£95 per m² installed.
GRP Fibreglass
Cold-applied liquid resin and mat, cures to a hard seamless surface. Walkable — ideal for balconies and roof terraces.
Best for: Walkable surfaces, balconies, terraces, complex shapes.
Lifespan: 25+ years. 25-year manufacturer warranties available.
Cost: £85–£110 per m² installed.
High-Performance Felt
Modern torch-on felt is a different beast to old felt. Three-layer systems with 20+ year lifespan at the lowest price point.
Best for: Garage roofs, outbuildings, dormers, budget-conscious installations.
Lifespan: 15-25 years depending on system.
Cost: £45–£70 per m² installed.
How to choose?
Go EPDM if: You want the longest-lasting, lowest-maintenance option and the roof isn’t walkable.
Go GRP if: You need a walkable surface (balcony, terrace) or have a complex shape.
Go felt if: Budget is the priority and it’s a garage or outbuilding.
We install all three and will always recommend what’s actually right for your situation — not what’s most profitable for us.