Roofers finishing a new EPDM rubber flat roof on a UK home extension

Flat roofing: EPDM, GRP and felt

New flat roofs for extensions, garages, dormers and balconies: which system suits your roof, what it costs in 2026, and up to three free quotes from vetted local roofers.

Quick answer: a new flat roof costs £80 to £150 per m² in 2026 depending on material. Felt is cheapest upfront, EPDM rubber usually cheapest per year of life, and GRP fibreglass the pick for walked-on or complex roofs. Vetted installers quote free through Expert Roofers.

Flat roofing covers every low-pitch roof on the average UK home: the extension, the garage, the dormer, the bay window and the balcony. Three systems dominate domestic work, and choosing between them matters more than most homeowners realise, because the right material on the wrong roof fails early no matter how well it is laid.

What flat roofing services cover

A flat roofing installer supplies and fits complete new coverings: single-sheet EPDM rubber membranes, wet-laid GRP fibreglass laminates and 3-layer torch-on felt systems, along with the trims, upstands, outlets and edge details that decide whether the roof actually stays watertight. New builds and extensions, re-covers of existing roofs, insulation upgrades and rooflight kerbs all sit within the service. If your existing flat roof has failed and needs stripping first, that job is covered on our flat roof replacement page, and localised faults on the flat roof repair page.

Which system suits which roof

Plain rectangle, rarely stepped on, tight budget: torch-on felt still does a job, laid as a proper 3-layer system.
Bigger, simpler roofs with few penetrations: EPDM rubber. It comes in large single sheets with no seams on most domestic sizes, flexes with the building and lasts 30 to 50 years.
Walked-on roofs, balconies, complex shapes and upstands: GRP fibreglass. It cures into a hard, seamless shell that takes foot traffic and tight detailing.
Roof terraces and green roofs: usually GRP or a reinforced membrane, engineered for the load; see green roofs.

Our flat roof material comparison puts all three side by side on cost, lifespan, looks and repairability if you want the full decision walkthrough.

How a new flat roof is installed

Survey and written spec. Deck condition, falls, insulation requirement and the material, all itemised in the quote.
Deck preparation. New boards on a new build; on a re-cover, rotten decking replaced at an agreed per-m² rate.
Insulation. On most wholesale re-covers, building regulations require the insulation to be brought up to current standards, usually as a warm roof build-up.
The covering. EPDM bonded in one sheet, GRP laid wet with matting and topcoat, or felt torched on in three layers.
Details and edges. Trims, upstands, outlets and flashings, which is where cheap jobs fail first.
Guarantee. A written product and workmanship guarantee, ideally insurance-backed.

What a new flat roof costs

Material	Supplied & fitted per m²	Lifespan
Felt (torch-on)	£80 – £110	10 – 20 years
EPDM rubber	£90 – £130	30 – 50 years
GRP fibreglass	£110 – £150	25 – 40 years

As whole jobs, a typical single garage runs £1,400 to £3,000 and a 25m² extension roof £2,300 to £4,000. The full flat roof cost guide covers job totals, insulation upgrades and the extras that change the bill.

Tip: judge materials on cost per year of life, not the day-one price. Felt is the cheapest to lay but the first to fail; EPDM costs a little more and can last two to three times as long, which is why it usually wins the value calculation on simple roofs.

Why use a vetted flat roofer

Flat roofs fail at the details: a poorly dressed upstand, a skimped layer, an outlet without a proper fall. Every installer in the Expert Roofers network is vetted for insurance, trading history and real customer feedback, and quotes must specify the full build-up in writing, so you can compare systems like for like before anything is signed.

Get real prices for your flat roof

Up to three itemised quotes from vetted local roofers, checked against the fair rates on this page. Free, no obligation.

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Flat roofing FAQs

Flat roofing questions, answered

Flat roof replacement costs £80 to £150 per square metre in 2026 depending on material: £80 to £110 for torch-on felt, £90 to £130 for EPDM rubber and £110 to £150 for GRP fibreglass, supplied and fitted. A typical single garage runs £1,400 to £3,000 and a 25 square metre extension roof £2,300 to £4,000. See the full flat roof cost guide.

Neither is better outright; they suit different roofs. EPDM rubber flexes with the building and comes in large single sheets, so it suits bigger, simpler roofs with few penetrations. GRP fibreglass sets as a hard, seamless shell, so it is harder wearing under foot traffic and handles complex shapes, upstands and details better. The flat roof comparison covers the trade-offs in full.

It depends on the material. Torch-on felt typically lasts 10 to 20 years, GRP fibreglass 25 to 40 years, and EPDM rubber 30 to 50 years. Installation quality matters as much as the material: a poorly detailed GRP roof can fail years before a well-laid felt one.

GRP fibreglass yes: it cures into a rigid laminate and is designed to take foot traffic, which is why it is the usual choice for balconies and roofs with regular access. EPDM rubber and felt tolerate occasional careful access only, so fit walkway pads over any route you will use often.

Usually yes when the covering is replaced wholesale rather than patched. Replacing more than a limited area counts as renovation of a thermal element, so the insulation may need to be brought up to current standards at the same time. A reputable roofer will handle the notification through a competent person scheme. See our building regulations guide.