newroofquote.uk

Flat roofs

Flat roof replacement cost calculator

Estimate the cost of replacing a flat roof — on an extension, dormer, garage or a flat-roofed home. Flat-roof pricing depends mostly on the system you choose and the area covered. Use the calculator for an instant indicative range, then get a fixed quote from a local roofer.

Flat roof replacement cost calculator

Scoped to flat roofs. Pricing depends mainly on the system and the area covered.

Figures are indicative UK ranges, last reviewed June 2026. A fixed price needs a free roof survey.

Bedrooms — a proxy for roof size

Flat-roof systems compared

  • EPDM rubber (around £75–£110/m²). The current mid-range standard. Single-sheet rubber membrane, typically lasting 25–35 years. The best all-round value for most flat roofs.
  • GRP fibreglass (around £85–£120/m²). A seamless fibreglass layer, well-suited to smaller areas like porches and extensions. Lifespan around 20–25 years.
  • Felt / torch-on (around £40–£65/m²). Cheapest upfront but shortest-lived at roughly 10–20 years. Often a false economy on a roof you intend to keep.
Building Regulations note: current Building Regulations usually require insulation upgrades ("warm deck" construction) when a flat roof is fully replaced, which adds a little per square metre. Your roofer will advise what's needed for your roof.

Flat roofs are common on extensions, dormers and garages. Because these are usually smaller sections than a whole pitched roof, the calculator biases the area down when you pick a flat roof on a house — a survey confirms the exact size.

This is an indicative estimate based on typical UK pricing. A fixed price needs a free roof survey from a local roofer.