The short answer
- A typical 18 m² garage roof costs £1,500–£2,600 in torch-on felt, £1,600–£2,800 in EPDM and £1,800–£3,250 in GRP.
- A 20 m² extension roof with a new deck and warm-roof insulation costs £2,800–£4,900 in EPDM.
- Patch repairs typically cost £150–£500.
- All prices include VAT at 20%, at West Midlands rates; the table below shows other regions.
How much do flat roofing systems cost per square metre?
Between £60–£105 and £90–£145 per m² for the membrane, laid on a sound deck, including stripping one existing layer.
| System | Per m² | Typical life | Guarantees |
|---|---|---|---|
| Torch-on felt (reinforced bitumen membrane) | £60–£105 per m² | 15–25 years | 10–20 year material guarantees on specified systems |
| EPDM rubber membrane | £65–£115 per m² | 25–50 years | 20-year material warranties are common |
| GRP fibreglass | £75–£140 per m² | 20–40 years | 20–25 year material warranties on specified systems |
| Cold liquid-applied membrane | £90–£140 per m² | 10–25+ years by product | 10, 15 or 20-year guarantees by named system |
| Single-ply membrane (PVC, TPO or FPO) | £90–£145 per m² | 25–35+ years | 20–25 year guarantees on specified systems |
| Mastic asphalt | £85–£150 per m² | 30–60 years | 15-year material, up to 25-year system guarantees |
What do typical flat roof jobs cost?
Whole-job guide prices with trims, waste and the extras listed.
| Job | Guide price inc VAT |
|---|---|
| Single garage (18 m²), torch-on felt | £1,500–£2,600 |
| Single garage (18 m²), EPDM rubber | £1,600–£2,800 |
| Single garage (18 m²), GRP fibreglass | £1,800–£3,250 |
| Extension (20 m²), EPDM, new deck + insulation | £2,800–£4,900 |
| Extension (20 m²), GRP, new deck + insulation | £3,000–£5,400 |
| Extension (20 m²), felt, new deck + insulation | £2,700–£4,700 |
| Dormer (8 m²), GRP, scaffold | £1,400–£2,650 |
| Porch or bay (4 m²), EPDM | £750–£1,250 |
| Balcony (12 m²), liquid-applied, scaffold | £1,900–£3,250 |
| Extension (20 m²), EPDM with sedum green roof | £4,400–£8,100 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,000–£5,250 |
| Commercial roof (100 m²), single-ply + insulation | £13,250–£21,800 |
| Block of flats (150 m²), felt + insulation + scaffold | £15,550–£27,200 |
| Mastic asphalt roof (30 m²), scaffold | £3,450–£6,250 |
| Single garage (18 m²), liquid-applied | £2,050–£3,250 |
| Single garage (18 m²), single-ply | £2,050–£3,350 |
What do the extras cost?
| Extra | Guide price |
|---|---|
| New OSB3 or plywood deck | £20–£35 per m² |
| Warm-roof insulation (PIR, vapour control layer) | £35–£60 per m² |
| Sedum green roof build-up | £80–£160 per m² |
| New edge and drip trims | £12–£22 per metre |
| Strip-out waste, skip and disposal | £250–£400 |
| Scaffold for a two-storey or dormer roof | £450–£950 |
| Rooflight upstand rebuilt and dressed (each) | £180–£350 |
| New outlet or gutter run | £120–£280 |
| Minimum charge for a full re-roof | £750–£1,250 |
How much do flat roof repairs cost?
| Job | Guide price inc VAT |
|---|---|
| Localised patch repair | £150–£500 |
| Upstand or flashing repair | £250–£650 |
| Outlet or drainage repair | £120–£350 |
| Emergency temporary weatherproofing visit | £180–£450 |
| Condition survey and leak investigation | £150–£300 |
How much more does a flat roof cost in London or less in the north?
We adjust the West Midlands baseline by region. The last column shows the 18 m² EPDM garage example.
| Region | Adjustment | EPDM garage roof |
|---|---|---|
| London | +20% | £1,900–£3,350 |
| South East | +10% | £1,750–£3,100 |
| East of England | +5% | £1,700–£2,950 |
| South West | +3% | £1,650–£2,900 |
| West Midlands | +0% | £1,600–£2,800 |
| East Midlands | -2% | £1,550–£2,750 |
| North West | -5% | £1,500–£2,650 |
| Yorkshire and the Humber | -5% | £1,500–£2,650 |
| North East | -7% | £1,500–£2,600 |
| Wales | -8% | £1,450–£2,600 |
| Scotland | -5% | £1,500–£2,650 |
| Northern Ireland | -12% | £1,400–£2,450 |
What's included in these guide prices?
Stripping one layer of the old covering, the new system with its trims, waste removal and VAT. New decking, insulation, scaffold, rooflight upstands and outlets are included only where listed. Not included: structural repairs to joists, asbestos testing or removal by a licensed specialist, building control fees where they apply, and making good inside.
Why is my quote different from the guide price?
Because the survey finds what a guide can't: a wet or rotten deck, poor falls, awkward access, extra upstands, or an existing roof that can't be overlaid. Your written quote lists each item so you can see where the price comes from. Read the full cost guide or work out your own guide price.
Sources: our own rates, checked against published 2026 UK cost guides (JobPrices, BestBuilders, MyJobQuote, LESS, RCB Group, Permaroof). Last checked 2026-11-09.
Questions about flat roof prices
How much does a new flat roof cost?
As a guide, re-covering an 18 m² single garage roof costs around £1,500–£2,600 in torch-on felt or £1,600–£2,800 in EPDM, including VAT. A 20 m² extension roof with a new deck and warm-roof insulation is around £2,800–£4,900 in EPDM. These are guide prices, and the fixed price comes after the free survey.
How much does a flat roof repair cost?
A localised patch repair is typically £150–£500, and an upstand, flashing or abutment repair £250–£650. An emergency temporary-weatherproofing visit is around £180–£450, and the fixed price for any permanent repair is confirmed once the roof has been inspected.
Is the survey and quote free?
Yes, for replacement and new roofs the survey and fixed written quote are free, with no obligation to go ahead. A condition survey with a written report, or a leak investigation, is a paid service, guide £150–£300.
What affects the price of a flat roof?
Roof size, the system chosen and the condition of the deck make the biggest difference. Insulation, access and scaffold, upstands, rooflights and outlets, height, waste disposal and region also affect the price. Small roofs cost more per square metre because set-up costs are spread over less area, and the minimum charge for a full re-roof is £750–£1,250.
Do your prices include VAT?
Yes, the guide prices on this site include VAT at 20%. Flat roof repair and replacement is standard-rated, and insulation fitted as part of a roof replacement is usually not split out at a lower rate, so we don't promise any VAT relief.