Flat roof replacement cost in 2026: felt, EPDM and GRP compared
Fitted 2026 prices per m² for felt, EPDM and GRP flat roofs, what a garage or extension roof costs, the extras a quote can leave out, and the rules in each UK nation.
Replacing a flat roof costs £800 to £6,500 in 2026 for the covering alone, from a porch to a large extension. A typical 25 m² extension roof runs £3,400 to £5,700 once insulation, scaffolding and sign-off are added, and most of the gap between quotes is what they include. We give prices per m² for felt, EPDM and GRP, the extras, how long each lasts, and the rules in each UK nation.
Flat roof replacement cost by roof
These are 2026 fitted prices for the covering: stripping the old roof, laying the new membrane and fitting the trims. They assume the timber deck underneath is sound. Insulation, scaffolding, a skip and any building control fee come on top.
| Roof | Typical area | Covering replaced |
|---|---|---|
| Porch or bay window | 5 – 8 m² | £800 – £1,500 |
| Single garage | 15 m² | £900 – £2,400 |
| Rear extension | 20 – 25 m² | £1,400 – £3,800 |
| Large extension | 35 – 45 m² | £2,200 – £6,500 |
The spread inside each row is the material. Felt sits at the bottom, EPDM in the middle and GRP at the top, and labour makes up 40 to 60% of the price whichever you choose.
A flat roof is priced on its own, separately from the main roof. If the house roof needs work too, replacing a pitched roof runs £4,000 to £20,000 on most houses, and doing both while one scaffold is up saves hiring it twice.
Flat roof cost per m² by material
Four coverings go on almost every UK flat roof. The table gives the fitted price per m² and what that comes to on three common roof sizes.
| Covering | Per m² | 15 m² garage | 25 m² extension | 40 m² extension | Lifespan |
|---|---|---|---|---|---|
| Felt (torch-on) | £40 – £70 | £900 – £1,300 | £1,400 – £2,000 | £2,200 – £3,200 | 15 – 20 years |
| EPDM rubber | £50 – £90 | £1,200 – £1,600 | £1,800 – £2,600 | £2,800 – £4,200 | 30 – 50 years |
| Single-ply PVC | £60 – £100 | Not priced | £2,000 – £2,800 | £3,000 – £4,400 | 25 – 35 years |
| GRP fibreglass | £80 – £130 | £1,800 – £2,400 | £2,800 – £3,800 | £4,200 – £6,000 | 20 – 40 years |
Small roofs cost more per m² than the rate suggests. The strip, the trims and the first day's labour are much the same on 15 m² as on 25 m², so a garage roof in felt lands at £900 rather than the £600 a straight £40 rate would give.
Felt and torch-on
Modern felt is a bitumen membrane laid in two or three layers and bonded with a torch. It is the cheapest covering at £40 to £70 per m² and lasts 15 to 20 years, with a good torch-on system reaching 25. It makes most sense on a garage or outbuilding where a shorter life is acceptable.
EPDM rubber
EPDM is a single sheet of synthetic rubber, either fully bonded to the deck or mechanically fixed. It costs £50 to £90 per m² and lasts 30 to 50 years. On a sound, dry deck it can sometimes go straight over the old felt, which saves stripping it.
GRP fibreglass
GRP is glass-reinforced plastic: layers of resin over a glass mat, finished with a coloured topcoat and often an anti-slip surface. At £80 to £130 per m² it is the dearest of the four, and it lasts 20 to 40 years.
Single-ply PVC
PVC membrane sits between EPDM and GRP on price, at £60 to £100 per m², and lasts 25 to 35 years. A 25 m² extension in PVC costs £2,000 to £2,800.
Felt, EPDM or GRP: price against lifespan
The cheapest covering is not the cheapest roof. On a 25 m² extension, felt costs £1,400 to £2,000 and lasts 15 to 20 years, so over 30 years it gets laid at least twice: £2,800 to £4,000 at today's prices. EPDM costs £1,800 to £2,600 once and lasts 30 to 50 years.
GRP costs more than EPDM up front. It earns that back on a roof that doubles as a balcony or terrace, where people walk on it, because it is laid as one continuous surface and takes an anti-slip finish.
Guarantees follow the same order. Material warranties run about 15 years on felt, 25 on GRP and 20 to 30 on EPDM, and a roofer's workmanship guarantee runs 10 to 25 years. Ask for both in writing, each with its length in years.
What a full flat roof replacement includes
Two quotes for the same extension roof can sit thousands of pounds apart without either being wrong. One prices the covering. The other prices the whole job: the strip, new deck boards where the old ones have rotted, insulation to current building regulations, the membrane with its trims and flashings, the upstands and outlets, the waste, and the sign-off.
A roofing contractor's fully managed price looks like this. It includes VAT, waste removal, edge detailing and building control sign-off, and it assumes a sound deck.
| Covering | Up to 15 m² | 15 – 30 m² | 30 – 60 m² |
|---|---|---|---|
| Three-layer felt | £2,000 – £3,000 | £3,000 – £5,500 | £5,500 – £9,500 |
| Torch-on felt | £2,200 – £3,500 | £3,500 – £6,500 | £6,500 – £11,000 |
| EPDM rubber | £2,500 – £4,500 | £4,000 – £8,000 | £7,000 – £14,000 |
| GRP fibreglass | £3,000 – £5,000 | £5,000 – £9,500 | £9,500 – £17,000 |
Built up line by line, a 25 m² rear extension in EPDM lands inside that band.
Extra costs to budget for
These are the lines that turn a covering price into a final bill. Some turn up on most jobs, and some only once the old roof is off.
| Extra | Typical cost | When it applies |
|---|---|---|
| Rotten deck boards | £25 – £60 per m² | Found when the old covering is stripped |
| Insulation upgrade | £800 – £1,500 | Renovating the roof to building regulations |
| Scaffolding or edge protection | £300 – £600 per week | Higher roofs and dormers |
| Skip hire, 8-yard | £200 – £400 | Taking the old roof away |
| Joist repairs | £50 – £100 each | Rot or sagging in the frame |
| Beam replacement | £300 – £800 each | Structural damage |
| Fascia or soffit | £15 – £30 per metre | Rotten edge timber |
| Lead flashings | £60 – £120 per metre | Where the roof meets a wall |
| Guttering repairs | £300 – £800 | Damaged or sagging gutters |
| New rooflight | £400 – £800 | Adding one while the roof is open |
| Internal ceiling repairs | £200 – £600 | Water damage below the roof |
| Structural engineer's report | £300 – £600 | A heavier or lighter covering than before |
| Parking permit | £50 – £200 | Streets with controlled parking |
The deck is the budget risk. Nobody can see its condition until the covering is off, so a quote with no rate per m² for rotten boards can grow on the first morning.
Height adds cost as well. The flat top of a dormer sits at loft level, so scaffolding goes on the quote at £300 to £600 a week for as long as the job runs.
A change of covering can reach the structure. A covering that is much heavier or lighter than the old one may need the roof strengthened or modified, so get a structural engineer or surveyor to check before work starts.
Flat roof replacement cost in London
Flat roof prices in London run 10 to 30% above the rest of the UK, and central London sits at the top of that band. Parking permits add £50 to £200 on streets with controlled parking, and tight rear access adds labour.
Outside London, use the UK ranges above as the benchmark. A quote well above them should say in writing what the extra money covers.
How long a flat roof replacement takes
| Job | Typical time on site |
|---|---|
| Single garage, 15 – 20 m² | 1 – 2 days |
| Extension in EPDM or felt, 15 – 30 m² | 1 – 3 days |
| Extension in GRP | 2 – 3 days |
| Large extension, 40 – 60 m² | 3 – 5 days |
Weather decides the calendar. GRP needs warm, dry weather, and a winter GRP job often cannot go ahead at all. EPDM and torch-on felt can be laid through more of the year, though rain slows any flat roof.
A full replacement runs in this order:
- The old covering is stripped and taken away, and the deck boards are checked.
- Rotten boards are replaced, along with any joist or fascia repairs.
- Insulation goes down where the job calls for it, usually as rigid PIR board.
- The new covering is laid, with its trims, flashings, upstands and outlets.
- The work is signed off, by the roofer's scheme or by building control, and the guarantees are handed over.
In a full renovation budget, the flat roof belongs near the front of the queue. Roofing comes before the final finishes, so the ceiling below is not decorated twice.
Building regulations for a new flat roof in England
In England, replacing roof coverings on flat and pitched roofs is on the government's list of work that needs building regulations approval. Some repairs to a flat roof do not need an application.
The insulation rule is what moves the price. Replacing the waterproof membrane on a flat roof counts as renovating it, and where the work covers more than 50% of the roof, the whole roof has to be brought up to the insulation standard, as far as that is technically, functionally and economically feasible.
There are two ways to get the work signed off. A roofer registered with a competent person scheme can self-certify it, and the certificate should arrive within 8 weeks of completion. Otherwise it goes to the council's building control, and on a building notice work can start 2 days after the notice goes in.
If you are converting the garage underneath at the same time, the roof stops covering an unheated space and has to meet the insulation standard for a heated room.
The standard tightens next year. The 2026 edition of Approved Document L, which takes effect in England on 24 March 2027, sets the improved U-value for a renovated roof at 0.16 W/m²K.
Planning permission
Replacing a flat roof like for like rarely needs planning permission, because it counts as repair and maintenance. A listed building needs listed building consent for any significant works, and a conservation area or an Article 4 direction can add restrictions, so check with the council first if the house is in one.
Flat roof rules in Scotland, Wales and Northern Ireland
The prices above apply across the UK. The approval rules do not:
- Wales has its own building regulations. Welsh Government guidance says most re-roofing needs approval, that some flat roof repairs do not, and that re-covering a roof should include improving its insulation. It recommends a roofer registered with a competent person scheme for flat roof coverings.
- Scotland uses building warrants. Under Scotland's building standards, replacing an external covering with material of the same general type needs no warrant, but the work must still meet the standards and be no worse than what was there. Whether EPDM replacing felt counts as the same general type is for the council's building standards team to confirm before work starts.
- Northern Ireland has separate building regulations, run by district council building control. Northern Ireland's energy guidance treats replacing a flat roof's waterproof membrane as renovating it, while a partial patch repair is not. Ask the council before a full replacement.
Repair or replace a flat roof
A leaking flat roof is usually a repair when the damage is in one place, the roof is inside its working life and the repair costs less than 20% of a new roof. Working life here means under 15 years for felt or torch-on and under 25 for EPDM or GRP.
Past that point, each patch buys less time. A roof with several patches is failing across its whole surface, and another patch treats one symptom of it.
Home insurance pays for storm, fire or accidental damage, not for a roof that has worn out. If a storm did the damage, photograph it and tell the insurer before any work starts, because most policies want more than one quote.
Common questions
How much does it cost to replace a flat roof?
A flat roof costs £800 to £6,500 to replace in 2026 for the covering alone, from a porch to a large extension. A single garage runs £900 to £2,400 and a 20 to 25 m² rear extension £1,400 to £3,800. A full job with insulation, scaffolding and building control costs about £3,400 to £5,700 on a 25 m² extension in EPDM.
How much does a flat roof cost per m²?
A new flat roof costs £40 to £70 per m² in felt, £50 to £90 in EPDM rubber, £60 to £100 in PVC and £80 to £130 in GRP fibreglass, fitted, in 2026. Those rates cover the strip, the new covering and the trims. Insulation adds £25 to £45 per m² and rotten deck boards £25 to £60 per m².
How often do flat roofs need replacing?
A flat roof needs replacing every 15 to 20 years in felt, 20 to 40 years in GRP and 30 to 50 years in EPDM rubber. Age alone is not the trigger. Pooling water 48 hours after rain, blisters, splits and leaks in more than one place are the signs a roof has reached its end.
Is EPDM cheaper than GRP?
EPDM is cheaper than GRP, at £50 to £90 per m² fitted against £80 to £130. On a 25 m² extension that is £1,800 to £2,600 for EPDM and £2,800 to £3,800 for GRP. EPDM also lasts longer, 30 to 50 years against 20 to 40, while GRP is the usual pick for a roof that doubles as a balcony.
How much does a garage flat roof replacement cost?
Replacing a single garage's flat roof costs £900 to £2,400 in 2026 for a roof of about 15 m². Felt costs £900 to £1,300, EPDM £1,200 to £1,600 and GRP £1,800 to £2,400. It usually takes 1 to 2 days, and rotten deck boards found under the old covering add £25 to £60 per m².
Can you claim for a new flat roof on your house insurance?
A claim covers a roof damaged by storm, fire or an accident, not one that has worn out with age. Wear and tear, lack of maintenance and problems that were already there are excluded. If a storm caused the damage, photograph it and tell the insurer before any work starts.
Can I replace a flat roof myself?
You can replace your own flat roof, but in England the work still needs building regulations approval. A homeowner cannot self-certify, so the job goes to the council's building control, for example on a building notice lodged at least 2 days before work starts. Renovating more than half the roof also means insulating the whole of it.
What time of year is best to replace a flat roof?
Late spring to early autumn is the easiest time to replace a flat roof, because GRP needs warm, dry weather and rain slows every covering. A winter GRP job often cannot go ahead at all. EPDM and torch-on felt can be laid through more of the year, so a winter replacement is usually one of those.
Do I need building regulations approval to replace a flat roof?
Replacing a flat roof covering needs building regulations approval in England, though some repairs do not. A roofer in a competent person scheme can self-certify the work, and otherwise it goes to the council's building control. Where more than 50% of the roof is renovated, the whole roof has to be insulated to the current standard as far as is feasible.
How long does it take to replace a flat roof?
A flat roof replacement takes 1 to 2 days on a single garage and 1 to 3 days on a typical extension in EPDM or felt. GRP takes 2 to 3 days, and a large 40 to 60 m² extension roof takes 3 to 5 days. Rain adds days to any of them.