Three materials dominate flat roofing in the UK: felt, GRP fibreglass and EPDM rubber. Each has a place. The right choice depends on your budget, your timeline, and how long you want the roof to last without thinking about it again.
Felt
Felt is the traditional option, and it’s still the cheapest to install. Costs typically run around £40–£95 per m². That’s roughly £1,200–£3,500 for a 25–30m² extension or garage roof, according to Checkatrade’s 2026 flat roof cost guide.
Modern torch-on and pour-and-roll felt systems are a big improvement on older versions. Even so, felt has the shortest lifespan of the three, at around 15–20 years. It can also be prone to blistering and splitting in strong sun.
GRP fibreglass
GRP fibreglass forms a single, seamless, rigid surface once it cures. That makes it very good at resisting standing water and foot traffic. It costs more than felt — typically £80–£140 per m², or around £2,400–£4,200 for a garage or extension roof.
It’s applied in multiple layers with a curing time between them, so installation takes longer than felt or EPDM. That means it’s worth planning around the weather. In return, you get a genuinely tough, low-maintenance roof with a lifespan of 30–40 years.
EPDM rubber
EPDM is a single-sheet rubber membrane, usually installed with far fewer joints than felt. That’s one reason it’s become the most popular choice for new flat roofs. Costs sit around £80–£120 per m² (£1,800–£3,200 for a typical garage or extension). It can often be fitted quickly in stable weather.
Its standout feature is longevity: a well-installed EPDM roof can last 40–50 years. That makes it the best value option over the life of the roof, even though felt looks cheaper on day one.
Which should you choose?
If budget is the only concern and the roof is small, felt remains a reasonable choice, provided you plan for a shorter lifespan. For a roof you want to forget about for decades, EPDM offers the best balance of cost and durability. GRP, meanwhile, suits roofs that will see heavy foot traffic, such as a roof terrace.
Whichever you choose, remember that scaffolding hire adds roughly £300–£600 per week on a two-storey property. So it’s worth timing a re-roof alongside other scaffolded work where possible.
If you’re not sure a full replacement is needed yet, our guide to flat roof repair vs replacement explains how to judge whether a repair will do instead.
We fit all three systems across Twickenham and St Margarets, as well as here in Teddington. We’ll always recommend the material that suits your roof, not just the one that’s quickest for us to fit.
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