---
title: "EPDM vs GRP vs Felt: Best Flat Roof?"
description: "EPDM rubber, GRP fibreglass, single-ply and felt flat roof materials compared on cost, lifespan and where each works best."
author: "Find Trusted Roofers"
published_at: 2026-07-05
canonical: "https://findtrustedroofers.co.uk/advice/flat-roof-materials"
tags: ["flat roof materials","epdm","grp fibreglass"]
---Flat roof materials have improved dramatically since the felt-only days. The choice between them is now genuinely worth thinking through, rather than defaulting to whatever's cheapest.

## The main flat roof materials

Four materials cover the vast majority of UK flat roofs. **EPDM rubber** is a single flexible synthetic rubber sheet. **GRP fibreglass** is a rigid, seamless laminate. **Single-ply membrane** uses larger welded synthetic sheets, common on bigger roofs. **Felt** is layered bituminous sheets, covered in detail in our [roofing felt guide](/advice/roofing-felt).

## EPDM rubber — pros & cons

EPDM is fitted as one continuous rubber sheet with minimal seams. This makes it fast to install and highly resistant to UK weather cycling, since the material expands and contracts through temperature swings without splitting. It's excellent on garages, extensions and dormers. Its main weak point isn't the material itself — properly cured EPDM is very durable. The real risk is installation quality: a poorly bonded seam or adhesive edge detail is where most EPDM failures start. Sharp objects or repeated foot traffic in one spot can also puncture it.

## GRP fibreglass — pros & cons

GRP is laid wet and cures into a rigid, fully bonded, seamless surface. This makes it a strong choice for balconies and walk-on roofs, where EPDM's flexibility is less of an advantage. Because it's rigid rather than flexible, GRP can crack if the timber deck beneath it moves. Deck stability matters more here than with EPDM. It also costs a little more, and application quality — correct resin mix, suitable weather during installation — has a big effect on how long it lasts.

## Single-ply — pros & cons

Single-ply membrane sits between EPDM and traditional felt in typical use. The sheets are larger than EPDM and welded, rather than glued, at the joints. It suits bigger flat roof areas well, including some commercial and larger domestic applications. Single-ply offers strong durability and a good cost-to-lifespan ratio, although it's specified less often than EPDM on small domestic jobs like a single garage.

## Felt — pros & cons

Modern high-performance torch-on felt is a legitimate, budget-friendly option for small, low-traffic roofs like sheds. See our [roofing felt](/advice/roofing-felt) guide for how it's laid and what to expect. It's the cheapest option and the shortest-lived. The old three-layer nailed felt that gave flat roofs their poor reputation is largely obsolete now, since modern torch-on and self-adhesive felts perform considerably better.

## Which lasts longest / costs least

As a rough ranking, felt is cheapest and shortest-lived at 10–20 years depending on grade. Single-ply sits in the middle on both cost and lifespan, at 20–25+ years. EPDM and GRP cost more upfront but last longest, at 25–30+ years, when properly installed. See our [roofing costs guide](/prices) for actual UK price ranges by roof size. The honest advice from most roofers: for anything bigger than a shed, EPDM or GRP pays for itself over the roof's lifetime versus repeated felt replacements.

Find Trusted Roofers connects UK homeowners with flat-roofing specialists who install EPDM, GRP and single-ply properly, since not every installer treats every material the same way. Tell us about your roof and we'll match you with a roofer covering your postcode.