Flat Roof Cost and Options UK: The Complete 2026 Guide

Flat roof cost in the UK is one of those figures that looks simple until you get three quotes and they are hundreds of pounds apart. The gap almost always comes down to the material and the specification, not the roofers being unreasonable. A felt roof and an EPDM rubber roof over the same garage are genuinely different jobs with different lifespans. This guide sets out what a flat roof costs in 2026 by material and by size, what pushes the price up, and how to compare quotes like for like before you commit. Always get at least three written quotes and check what each one actually includes.

What does a flat roof cost in the UK?

As a rough guide for a supplied-and-fitted flat roof in 2026, expect:

• Felt (built-up torch-on): around £40 to £70 per square metre.
• EPDM rubber: around £80 to £120 per square metre.
• GRP fibreglass: around £70 to £110 per square metre for a standard system.

Those are covering costs. On a real job you also pay for stripping the old roof, any new timber deck or insulation, edge trims and, on anything above single storey, scaffolding. That is why the per-square-metre figure and the final bill can look so different.

Typical flat roof costs by size

Putting the rates against common jobs gives a more useful picture:

• A typical garage (around 15m²): roughly £600 to £2,250 fitted, depending on material, with felt at the bottom and GRP at the top.
• A single-storey kitchen extension (around 20m²): roughly £1,000 to £1,800 in EPDM, or about £1,600 to £2,600 in GRP fibreglass.
• A larger extension or multiple roofs: scales up from there, and complexity (upstands, rooflights, parapet walls) adds cost.

For a like-for-like comparison with a pitched roof on the same building, see our guide to flat roof vs pitched roof cost.

The three main flat roof materials

Felt. The traditional and cheapest option, now usually torch-on built-up felt rather than the old cold-applied kind. It is fine on a budget or a garage, but has the shortest life of the three, typically 15 to 20 years.

EPDM rubber. A single-sheet rubber membrane that has become the go-to for domestic flat roofs. It is mid-priced, quick to fit on simple roofs, and long-lived: a well-installed EPDM roof commonly lasts 25 to 40 years. For most homeowners it is the best balance of cost and lifespan.

GRP fibreglass. A glass-reinforced plastic laid up wet and cured into a seamless, hard-wearing surface. It is the most expensive of the three and gives an excellent finish, especially where the roof is walked on or seen, but the topcoat may need renewing after 15 to 20 years to keep its UV protection. It is also weather-sensitive to install.

Our full EPDM vs GRP vs felt comparison weighs these up in detail.

The extra costs people forget

The covering is only part of a quote. Watch for these line items, and be suspicious of any quote that leaves them out:

• Stripping and disposal of the old roof: often £500 to £1,000 depending on size and what is up there.
• New deck and insulation. Building Regulations Part L expects a warm, well-insulated roof on habitable rooms, and a rotten deck must be replaced regardless.
• Scaffolding or edge protection on two-storey work: commonly £300 to £600 a week. A garage may only need a tower.
• Trims, flashings and rooflights. Lead or GRP upstands where the flat roof meets a wall, and any Velux-style lights, add labour and materials.

What changes the price most

Beyond material, the big drivers are size, access and complexity. A simple rectangular garage roof at ground level is cheap; a two-storey extension roof with parapet walls, multiple penetrations and awkward access costs far more per square metre. The condition of what is underneath matters too: a sound deck keeps the job simple, while widespread rot turns a re-cover into a rebuild. Region plays a part, with London and the South East higher than the rest of the UK.

How to compare flat roof quotes

Get three written quotes and make sure each states the material and system (not just “new flat roof”), whether it includes stripping and disposal, the insulation spec, and the guarantee. A longer manufacturer-backed guarantee on EPDM or GRP is worth more than a cheap felt job that needs redoing in 15 years. Check the roofer is experienced with the specific system, since EPDM and GRP are both installation-sensitive, and confirm whether the price includes VAT. For repairs rather than replacement, our roof repair cost guide covers patching a leak instead. Building Regulations for roof insulation are set out in the government’s Approved Document L, which is worth a look before you sign off a spec.

Frequently asked questions

How much does a flat roof cost in the UK? As a 2026 guide, felt runs about £40 to £70 per square metre, EPDM rubber about £80 to £120, and GRP fibreglass about £70 to £110, all supplied and fitted. A typical garage costs roughly £600 to £2,250 and a single-storey extension roof roughly £1,000 to £2,600 depending on material.

Which flat roof material is cheapest? Felt is the cheapest to install, but it has the shortest lifespan at around 15 to 20 years. EPDM rubber costs more up front but lasts far longer, so it is often cheaper over the life of the roof.

How long does a flat roof last? It depends on the material: felt around 15 to 20 years, GRP fibreglass around 20 to 30 years with topcoat renewal, and a well-installed EPDM rubber roof commonly 25 to 40 years.

Do you need scaffolding for a flat roof? For a two-storey roof or extension, usually yes, at roughly £300 to £600 a week, and it is a legitimate safety cost. A ground-level garage may only need a scaffold tower or edge protection, which is cheaper.

Is EPDM or GRP better for a flat roof? EPDM is usually the better value for a standard domestic flat roof thanks to its long life and quick installation. GRP gives a harder, seamless finish that suits roofs that are walked on or on show, but it costs more and needs its topcoat renewing over time.

Does a new flat roof need Building Regulations? Replacing more than a set proportion of a roof, or covering a habitable room, brings Building Regulations into play, particularly the insulation requirements in Approved Document L. A reputable roofer will factor this in and can arrange the necessary sign-off.