Flat roof materials UK: EPDM vs GRP vs felt vs PVC compared
Four main flat roof materials in the UK, with very different lifespans and costs. EPDM is the long-term winner; felt is the budget choice; GRP and PVC sit in between.
EPDM (ethylene propylene diene monomer)
A single rubber sheet, glued or mechanically fixed to insulation. The longest-lasting domestic flat-roof material — 40-50 years from quality manufacturers (Firestone RubberCover, Carlisle). One-piece installation means very few joints, so very few leak points.
Cost: £40-100/m² installed. The wide range reflects roof size (smaller roofs cost more per m²), insulation spec, and whether you go for a top brand or generic.
Best for: domestic extensions, garage roofs, dormers. The default choice for new flat roofs in 2026.
GRP (glass-reinforced plastic, fibreglass)
Laid as multiple layers of fibreglass mat saturated with polyester resin, building up a continuous waterproof skin. Once cured, GRP is rigid and walkable. No seams (it's continuous), but harder to repair if damaged.
Lifespan: 25-30 years. Cost: £60-120/m². More expensive than EPDM and shorter-lived, but rigid surface is good for balcony / terrace use where people walk on it.
Best for: balconies, walked-on terraces, dormers with tight detailing.
Bitumen felt (built-up felt roofing)
Multiple layers of bitumen-saturated felt, torched-on or self-adhesive. The traditional UK flat-roof material, used since the 1950s. Cheapest option but shortest lifespan.
Lifespan: 10-20 years (modern polyester-reinforced bitumen lasts longer than 1960s versions). Cost: £35-75/m².
Best for: budget jobs, small areas (sheds, porches, garages where 15-year lifespan is acceptable). See our felt roof guide for details.
Single-ply PVC / TPO
Large pre-formed sheets of PVC (polyvinyl chloride) or TPO (thermoplastic polyolefin), heat-welded at the seams. Common on commercial roofs. Growing in domestic use.
Lifespan: 25-30 years. Cost: £60-100/m². Looks more "industrial" than EPDM. Best installed by specialists (heat-welding seams correctly is harder than gluing EPDM).
Best for: large commercial or commercial-style domestic flat roofs.
Comparison table
| Material | Lifespan | Cost/m² | Best for |
|---|---|---|---|
| EPDM | 40-50 yrs | £40-100 | Domestic extensions, garages |
| GRP | 25-30 yrs | £60-120 | Balconies, terraces, walked-on |
| Felt | 10-20 yrs | £35-75 | Sheds, porches, budget |
| Single-ply PVC | 25-30 yrs | £60-100 | Large commercial-style |
| Liquid rubber (Acrypol etc.) | 10-15 yrs | £25-50 | Refurb over existing flat roof |
| Asphalt mastic | 30-50 yrs | £80-150 | Listed / heritage flat roofs |
- Best domestic flat roof
- EPDM (longest lifespan, lowest cost-per-year)
- Best for balconies
- GRP (walkable surface)
- Cheapest option
- Felt
- Best for heritage
- Asphalt mastic
How to choose
- How long will you stay? 15+ years: EPDM. 5-15 years: felt (the cheap upfront cost wins). Forever: asphalt mastic if the property is listed.
- Will anyone walk on it? Yes: GRP. No: EPDM.
- Is it visible? EPDM looks darker/matt-black. GRP can be coloured (popular grey, green). PVC looks plastic. Bitumen felt looks utilitarian.
- Budget tight? Felt for 15 years, then plan to redo. Don't get sold "liquid rubber" as a primary roof — it's a refurb product.
Insulation considerations
Building Regulations Part L requires modern flat roofs to be insulated to U-value 0.18 W/m²K or better (warm-roof construction with insulation above the deck). Add £40-60/m² for the insulation board layer. Older flat roofs ("cold roof" construction with insulation between joists) usually need an upgrade when re-covered.
Sources
- Checkatrade, Flat roof material cost guide, 2026
- NFRC, Flat Roof Installation Guide, 2025 edition
- Firestone RubberCover, Carlisle EPDM, Sika Sarnafil product data sheets
- Building Regulations Approved Document L (Conservation of fuel and power), 2024
Last reviewed: 2026-05-18