Flat Roof Replacement Cost in 2026: UK Prices for Felt, EPDM and GRP
Drawn from published 2026 UK cost data. Use the figures to read a quote, not as a quote.
A flat roof replacement cost in the UK comes down to three things: how big the roof is, which covering goes on it and what state the timber underneath is in. Pin those three down and a quote stops looking like a guess. The prices here come from ten UK cost guides published in 2026, including Costwise, FixMyRoof, BestBuilders and Expert Roofer. Where the guides disagree, you get both figures.
In 2026, most UK garage flat roofs cost £1,200–£2,500. A single-storey extension costs about £2,300–£4,000, or £4,250–£7,500 with a new deck and insulation. Felt is cheapest per square metre but wears out first. EPDM usually works out cheapest per year of use. GRP costs the most and takes foot traffic.
Flat Roof Replacement Cost per Square Metre in 2026
Flat roofers quote a fitted price per square metre, with the materials included. The rates below assume the old covering comes off and the new one goes onto a sound deck. Every guide puts the three coverings in the same order: felt first, EPDM in the middle and GRP at the top.
| Covering | Fitted price per m² (2026) | Typical lifespan | Best suited to |
|---|---|---|---|
| Torch-on felt | £40–£80 | 10–20 years | Garages and sheds on a tight budget |
| EPDM rubber | £70–£110 | 30–50 years | Garages and extensions nobody walks on |
| GRP fibreglass | £90–£130 | 25–30 years | Balconies, terraces and roofs with lots of upstands |
- Torch-on felt: £40–£60 per m² on FixMyRoof's figures, up to £60–£80 per m² on Costwise's.
- EPDM rubber: £70–£110 per m² in both Costwise and BestBuilders, with FixMyRoof lower at £50–£80.
- GRP fibreglass: £90–£130 per m² in both Costwise and Up Top Roofing. FixMyRoof puts a fully specified system, with trims, upstands and a topcoat, at £95–£120.
The spread comes from what each guide counts. Some price the membrane on a clean deck. Others fold in the strip-off, the trims and VAT. So a flat roof replacement cost quoted per square metre means little until you know what it covers.
Where you live moves the rate too. Costwise treats the Midlands as its UK average, at a typical £90 per m², and BestBuilders uses the Midlands as its baseline. London sits about 20% higher on the Costwise figures, and nearly all of that gap is labour.
Felt, EPDM or GRP: Which Covering Suits Your Roof
The price per square metre is only half the choice. Each covering behaves in its own way once it's down, and the right one depends on how you use the roof.
Felt goes down in layers, bonded with a gas torch. It's the budget option and still common on garages and sheds. Its weak spots are the laps between sheets and the upstands where the roof meets a wall. Blisters and splits tend to show up there first.
EPDM is a sheet of synthetic rubber glued to the deck. On most garages and small extensions it goes on in one piece, so there are almost no joins to fail. It stretches as the roof warms and cools. It will take the odd careful step, but it isn't made for regular walking.
GRP is resin laid over a glass-fibre mat and finished with a coloured topcoat. It sets into a hard skin with no joins, and you can walk on it, which is why it's the usual pick for balconies and roof terraces. It needs dry, mild weather to cure, and it can crack if the deck under it moves. With GRP, hiring a roofer who lays it every week matters more than with the other two.
Flat Roof Replacement Cost for a Garage, Extension or Larger Roof
Size sets the total. Small roofs cost more per square metre, because every job carries fixed costs for setting up, stripping and clearing away. FixMyRoof notes that many roofers have a minimum charge of £300–£500, which pushes up the rate on a porch or a bay.
| Roof | Typical price (2026) | What it covers |
|---|---|---|
| Single garage, about 15–20 m² | £1,200–£2,500 | New covering, strip-off and trims |
| Single-storey extension, about 25 m² | £2,300–£4,000 | New EPDM or GRP covering |
| Same extension, fully rebuilt | £4,250–£7,500 | New deck and warm-roof insulation as well |
| Larger roof, about 50 m² | £3,750–£6,000 | Covering only; £8,500–£15,000 fully rebuilt |
- Single garage (about 15–20 m²): most jobs cost £1,200–£2,500, per BestBuilders. For a 15 m² garage, Costwise gives £1,200–£1,800 in felt and £1,650–£2,700 in EPDM or GRP.
- Single-storey extension (about 25 m²): Expert Roofer puts EPDM at £2,300–£3,500 and GRP at £2,800–£4,000. Up Top Roofing gives £1,875–£3,000 for a standard replacement.
- The same extension, fully rebuilt: per Up Top Roofing, the bill is £4,250–£7,500 once the deck and insulation are renewed. BestBuilders prices a 35 m² EPDM roof with a warm-roof upgrade at £4,730–£6,130.
- Larger roof (about 50 m²): Up Top Roofing gives £3,750–£6,000 for a standard replacement. A full strip and rebuild costs £8,500–£15,000, it says. For EPDM on a 30–60 m² roof, Countrywide Insulation quotes £7,000–£14,000.
Countrywide's figures run higher than most across the board, because they include VAT, waste and edge details as standard. That's a useful warning. Two quotes for the same roof can sit thousands apart just because one of them lists more of the work.
The Deck, the Joists and the Falls
The covering sits on a deck of timber boards, usually OSB or plywood, laid over the joists. When a flat roof has leaked for a few winters, those boards soak up water and go soft. Nobody can tell how far the rot has spread until the old covering is off.
Costwise adds £20–£45 per m² for a new deck, and Expert Roofer adds £20–£35. BestBuilders puts new boards over sound joists at about £850 on a typical job. The figure rises to about £1,800, according to the same guide, once rot has reached the joists themselves.
Ask every roofer for a rate per square metre for new boards before work starts. That way a soft patch found on the first morning doesn't turn into an open-ended bill. It also lets you compare quotes that assume different things about the deck. Of all the lines on a quote, the deck is the one most likely to move a flat roof replacement cost after the job has begun.
The deck sets the falls as well. A flat roof should slope gently towards its outlet, and Roof Cost Calculator gives a minimum fall of 1:80. Water that sits on the roof for days after rain tells you the fall has gone. Tapered firrings or shaped insulation boards put it back, and they belong on the quote.
Insulation and Part L: the More-Than-Half Rule
Building Regulations Part L covers the insulation in a roof. If you renovate more than half of a roof, the roof has to meet current insulation standards. Costwise, BestBuilders and Up Top Roofing all put that line at 50% of the roof. Some guides print a lower figure, but it comes from a separate test for the whole outside of a house, not for a roof on its own.
In practice, a full replacement almost always crosses the line. Most roofers now quote a warm roof, where rigid insulation boards sit above the deck and under the new covering. That keeps the timber warm and dry. It also stops the condensation that rots older cold-built roofs from below.
Expert Roofer adds £40–£60 per m² for the warm-roof upgrade, and Countrywide Insulation adds £25–£45. If one quote for an extension roof comes in well below the rest, check whether the roofer left the insulation out.
A roofer registered with a competent person scheme, such as NFRC CompetentRoofer, can self-certify the work. If yours isn't registered, building control needs telling before the job starts. This is general information, not advice, so ask which route each price assumes.
Scaffold, Skips, VAT and Other Extras
A ground-floor garage roof can usually be reached from a ladder or a tower. A first-floor roof or a dormer needs more. FixMyRoof puts domestic scaffold at £300–£800, and BestBuilders adds about £450 for a tower or £900 for a full scaffold. Costwise prices it by area instead, at £15–£35 per m².
Stripping an old roof makes a lot of waste, and it has to leave the site in a skip or a van. Check that disposal is in the price. A quote can look cheaper just because that line is missing.
Look for the edge trims and drip edges too, plus the upstands and outlets. On a garage they're small items. On an extension roof with a rooflight and two walls to seal against, they take real time and money. Together, these small lines explain much of the gap in flat roof replacement cost between two roofers.
VAT at 20% applies to most flat roof work on a lived-in home, according to FixMyRoof. Ask whether each price you get includes it, because some guides and some quotes leave it off.
Repair or Replace a Flat Roof
Not every leak means a new roof. If the damage sits in one spot, such as a split at an upstand or a lifted seam, and the boards under it are firm, a repair makes sense. Countrywide Insulation backs repair when the roof is well inside its expected lifespan and the fix costs under 20% of a new roof. FixMyRoof's rough cut-off is 50%, and past that point it says replace.
The signs point the other way when the trouble is spread out. Watch for water still sitting on the roof 48 hours after rain, blistering across 20–30% of the surface, boards that feel soft underfoot and ceiling stains that come back after a patch. Several leaks in different places usually mean the whole system has failed. A patch over wet insulation only buys a few months.
A repair on a sound roof costs a fraction of the flat roof replacement cost, so get the deck checked before you agree to either. Don't climb onto the roof yourself to check. Look from an upstairs window or the garden, and look at the ceiling underneath.
How Long a Flat Roof Lasts in the UK
Lifespans vary more between guides than prices do, but the order stays the same.
- Felt: 10–15 years for basic felt, per FixMyRoof and Up Top Roofing. Better torch-on systems reach 15–20 years.
- EPDM: 30–50 years in BestBuilders, Expert Roofer and Countrywide Insulation. FixMyRoof is more cautious at 25–50.
- GRP: 25–30 years in Costwise and BestBuilders, with Expert Roofer allowing up to 40.
All of these figures assume a sound deck and a proper fall. FixMyRoof works the price out per year of use. Felt comes to about £4 per m² per year, against about £2–£2.50 for EPDM. That's why EPDM, though it costs more to lay, often turns out the cheaper roof over time.
Verdict: Judging a Flat Roof Replacement Cost in 2026
Start with the size of the roof. For a garage in 2026, most UK homeowners will see £1,200–£2,500. For the covering on an extension, expect £2,300–£4,000. A full rebuild with a new deck and warm-roof insulation lifts an extension to £4,250–£7,500.
Then pick the covering for the way you use the roof. EPDM is the safe choice for most garages and extensions. GRP earns its higher price where you'll walk on the roof. Felt makes sense only when the budget is tight and the building won't be kept long.
Last, test every quote on two points: the rate for new boards if the deck is soft, and whether the insulation meets Part L. The flat roof replacement cost worth trusting is the one with both answers in writing.
Getting a Quote in Telford
Across Telford's estates, flat roofs sit over garages, link blocks, single-storey extensions and porches. They tend to be the roofs that show wear first: a blister beside an upstand, water that stays put after rain, or a damp patch on the garage ceiling.
Tell us what the roof is doing, roughly how big it is and what covering it has now, and your enquiry goes to a local roofing firm that does flat work. We don't do the work, and we don't inspect or check the firm, so put the questions in this guide to them before you agree a price. See flat roofing for what the job involves and how to choose a roofer for the checks worth making.
Common Questions
How much does it cost to replace a flat roof in the UK?
In 2026, most UK flat roof replacements cost between £1,200 and £7,500. A garage roof usually costs £1,200–£2,500. For the covering alone, a single-storey extension costs about £2,300–£4,000. With a new deck and insulation, it's £4,250–£7,500. EPDM and GRP cost more than felt per square metre but last far longer.
How much does a flat garage roof cost to replace?
In 2026, replacing the roof on a single garage of about 15–20 m² costs £1,200–£2,500. Felt sits at the bottom of that band. EPDM and GRP sit higher. On Costwise's figures they cost about £1,650–£2,700. If the boards under the old covering have rotted, add £20–£45 per m² for a new deck on top.
Should I choose EPDM or GRP for my flat roof?
EPDM suits a roof you won't walk on, such as a garage or a small extension. It goes on as one sheet and most guides quote it at 30–50 years. GRP suits a balcony, a terrace or a roof with lots of upstands, because it sets hard. GRP costs more, at £90–£130 per m², and needs dry weather.
How long does a flat roof replacement take?
A garage or small extension roof in EPDM usually takes one to two days. GRP takes two to three days, because the resin needs time to cure. Larger roofs can run to four or five days. Rotten boards found under the old covering add time, and wet weather slows every type of flat roof work.
Will replacing a flat roof need building control sign-off?
Usually, yes. Renovating more than half of a roof brings in Part L, so the insulation has to meet current standards. A roofer in a competent person scheme, such as NFRC CompetentRoofer, can self-certify the work. If not, building control needs telling before work starts. This is general information, not advice, so check with your roofer.
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