EPDM vs GRP: Which Flat Roof System Is Best for Your East London Home?

If you need a new flat roof on your East London property, the two premium options are EPDM rubber and GRP fibreglass. Both are vastly superior to traditional felt, but they have different strengths. Here is an honest comparison to help you choose the right system for your property.

EPDM Rubber — The Facts

What it is: EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber membrane laid in a single piece and bonded to the roof deck with adhesive. No heat, no flames, no joints.

Guarantee: 20 years (manufacturer). Typical lifespan: 30–40 years.

Cost: £60–80 per m² installed in East London.

Best for: Larger flat roof areas (garages, commercial roofs), roofs that need to accommodate building movement, budget-conscious installations where the priority is long lifespan at lower cost.

Pros: Flexible — stretches up to 300% without tearing. Unaffected by temperature extremes. Single-piece installation means no seams to fail. Lightweight — no additional structural load. Can be installed in any weather. Lower cost than GRP.

Cons: Not walkable for regular foot traffic. Can be punctured by sharp objects. Not as rigid — will not bridge gaps in the deck. Joins at upstands require careful detailing.

The Single Ply Roofing Association (SPRA) reports that correctly installed EPDM membranes have a proven track record of 40+ years in service without significant degradation, exceeding typical manufacturer warranty periods. Source: SPRA Technical Guide.

GRP Fibreglass — The Facts

What it is: GRP (Glass Reinforced Polyester) is a fibreglass mat saturated with catalysed resin that cures to form a rigid, seamless shell bonded to the deck.

Guarantee: 25 years (manufacturer). Typical lifespan: 30–50 years.

Cost: £75–95 per m² installed in East London.

Best for: Smaller areas (extensions, dormers, balconies), roofs that will be walked on, roofs with complex detailing, areas where a rigid surface is needed.

Pros: Seamless and rigid — stronger than the deck beneath it. Walkable. Excellent for complex details and upstands. Available in multiple colours. Can be given non-slip finish for balconies. 25-year guarantee is the longest of any flat roof system.

Cons: More expensive than EPDM. Temperature-sensitive during installation (above 5°C required). Rigid — can crack on very large areas with significant building movement. Requires skilled application — resin mixing and timing are critical.

Side-by-Side Comparison

Cost per m²: EPDM £60–80 vs GRP £75–95. Winner: EPDM.

Guarantee: EPDM 20 years vs GRP 25 years. Winner: GRP.

Walkability: EPDM limited vs GRP fully walkable. Winner: GRP.

Flexibility: EPDM excellent vs GRP rigid. Winner: EPDM.

Installation weather: EPDM any conditions vs GRP above 5°C. Winner: EPDM.

Complex detailing: EPDM good vs GRP excellent. Winner: GRP.

Our Recommendation for East London

For rear extensions and dormer tops: GRP. The rigid surface handles foot traffic during maintenance, the 25-year guarantee is reassuring for a home’s most visible flat roof, and the seamless finish handles complex junctions better.

For garages and outbuildings: EPDM. The lower cost makes more sense for secondary structures, the single-piece membrane is reliable, and the 20-year guarantee is more than sufficient.

For balconies and roof terraces: GRP with non-slip finish. The walkable, rigid surface is essential for these applications.

Not sure which system is right for your property? Call 0203 441 9626 for free, honest advice. We install both systems and will recommend whichever is genuinely best for your situation.