Key points
- Re-covering a sound deck costs £60–£105 per m² in torch-on felt, £65–£115 per m² in EPDM and £75–£140 per m² in GRP, including VAT.
- A new deck, insulation, scaffold and rooflight upstands are priced as extras and often move the total more than the choice of membrane.
- Repairs start at £150–£500 for a localised patch, but repeated leaks on an ageing roof usually point to replacement.
- Compare quotes line by line, checking scope, build-up, deck allowance, building regulations and written guarantees.
How much does a flat roof cost per square metre?
Re-covering a sound deck costs £60–£105 per m² in torch-on felt, £65–£115 per m² in EPDM rubber and £75–£140 per m² in GRP fibreglass, including VAT and the strip-off of one existing layer. Liquid-applied, single-ply and mastic asphalt sit higher.
| System | Guide rate (inc VAT) | Typical service life |
|---|---|---|
| Torch-on felt | £60–£105 per m² | 15–25 years |
| EPDM rubber | £65–£115 per m² | 25–50 years |
| GRP fibreglass | £75–£140 per m² | 20–40 years |
| Liquid-applied | £90–£140 per m² | 10–25+ years, by product |
| Single-ply | £90–£145 per m² | 25–35+ years |
| Mastic asphalt | £85–£150 per m² | 30–60 years |
These rates cover the membrane and the labour to lay it. A new deck, insulation, scaffold, edge trims and waste disposal are priced separately. Small roofs cost more per square metre than large ones, because set-up, travel and detailing take much the same time on a 6 m² porch as on a 25 m² extension. For that reason a full re-roof carries a minimum charge of £750–£1,250. Service lives assume good specification and maintenance; see how long a flat roof lasts.
What does a typical flat roof job cost from start to finish?
Most complete domestic jobs fall between £750–£1,250 for a small porch and £3,000–£5,400 for an insulated extension roof in GRP. The examples below include strip-off, waste, trims and the extras listed, with VAT.
| Job | Assumptions | Guide price |
|---|---|---|
| Single garage, torch-on felt | 18 m², sound deck | £1,500–£2,600 |
| Single garage, EPDM | 18 m², sound deck | £1,600–£2,800 |
| Single garage, GRP | 18 m², sound deck | £1,800–£3,250 |
| Single garage, liquid-applied | 18 m², sound deck | £2,050–£3,250 |
| Single garage, single-ply | 18 m², sound deck | £2,050–£3,350 |
| Extension roof, torch-on felt | 20 m², new deck, warm-roof insulation | £2,700–£4,700 |
| Extension roof, EPDM | 20 m², new deck, warm-roof insulation | £2,800–£4,900 |
| Extension roof, GRP | 20 m², new deck, warm-roof insulation | £3,000–£5,400 |
| Extension roof, EPDM with rooflight | As above plus one rooflight upstand | £3,000–£5,250 |
| Extension roof, EPDM with sedum | As above plus green roof build-up | £4,400–£8,100 |
| Dormer roof, GRP | 8 m², scaffold | £1,400–£2,650 |
| Porch or bay roof, EPDM | 4 m² | £750–£1,250 |
| Balcony, liquid-applied | 12 m², scaffold | £1,900–£3,250 |
| Mastic asphalt roof | 30 m², scaffold | £3,450–£6,250 |
| Commercial roof, single-ply | 100 m², insulation | £13,250–£21,800 |
| Block of flats, torch-on felt | 150 m², insulation, scaffold | £15,550–£27,200 |
For your own roof size and system, the guide-price tool gives a range, and the full cost guide lists every rate we use. Larger roofs are covered under commercial flat roofing and flats and block roofs.
What makes a flat roof cost more or less?
Size and system set the baseline, but the condition of the deck and the access usually decide where in the range a job lands.
- Deck condition. A rotten or swollen chipboard deck has to come out. A new OSB3 or plywood deck adds £20–£35 per m², and on older roofs it is often needed across the whole area.
- Insulation. Bringing a roof over a heated room up to current standards adds £35–£60 per m², and it is usually required when more than half of that roof is replaced. See warm, cold and inverted roofs.
- Access and height. Single-storey roofs can often be worked from towers with edge protection; dormers and two-storey roofs need scaffold.
- Details. Every rooflight, soil pipe, chimney, outlet and abutment wall adds labour.
- Falls and drainage. A roof that holds water needs firrings or tapered insulation to correct the fall, which no patch can do. Read more about ponding water.
- Hidden problems. If asbestos is suspected, a licensed specialist surveys and removes it before work starts, and that cost sits outside the roofing price.
What do extras such as scaffold, trims and waste cost?
Scaffold for a two-storey or dormer roof costs £450–£950, strip-out waste and a skip £250–£400 and new edge trims £12–£22 per metre; each extra should appear on its own line in a written quote.
| Item | Guide price (inc VAT) |
|---|---|
| New OSB3 or plywood deck | £20–£35 per m² |
| Warm-roof insulation with 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 |
Where nobody can tell how much of the deck is sound until the old covering is off, a good quote states a square-metre rate for replacement boards, so there is no open-ended cost. Building control fees, where approval is needed, are set by the council or approver and shown separately.
Do flat roof prices vary across the UK?
Yes. Labour, scaffold hire, parking and waste disposal cost more in some areas than others, so the same roof can be priced differently in London than in Wales or Northern Ireland.
The figures in this guide use a West Midlands baseline. Our regional and town pages adjust them for local costs, with London and the South East typically at the top and much of Wales, the North and Northern Ireland lower. Weather plays a part too. Roofs on exposed coasts, on high ground and in the north and west face more wind, so the fixing pattern is specified for the site to resist uplift. Wetter areas also lose more working days to rain, because none of the main systems can be laid on a wet deck.
How much does a flat roof repair cost compared with a replacement?
A localised patch repair costs £150–£500, a fraction of a re-roof, so repair makes sense when the rest of the roof is sound.
| Repair | Guide price (inc VAT) |
|---|---|
| Localised patch repair | £150–£500 |
| Upstand, flashing or abutment repair | £250–£650 |
| Outlet or drainage repair | £120–£350 |
| Emergency temporary weatherproofing visit | £180–£450 |
| Condition survey and leak investigation report | £150–£300 |
The sums change when leaks keep coming back. Several call-outs on an ageing roof can add up to a large share of a new one, and no repair dries out wet insulation or stiffens a sagging deck. Our guide on whether to repair or replace sets out the signs. If water is coming in now, we offer an emergency temporary weatherproofing visit as soon as a team is available.
Is VAT charged on a new flat roof?
Yes. Flat roof repair and replacement is standard-rated at 20%, and every guide price on this site includes it.
HMRC treats an insulated roof replacement as a single standard-rated supply. A separate relief applies to qualifying installations of energy-saving insulation in homes, zero-rated until 31 March 2027 and 5% after that, but insulation fitted as part of a roof replacement is usually not split out from the rest of the job. We do not promise VAT relief on roofing work. When comparing quotes, check that each one says whether VAT is included: a price shown without it looks a sixth cheaper than it really is.
How do you compare flat roof quotes fairly?
Compare quotes line by line rather than on the total, because two prices for a new flat roof can describe very different jobs.
- Area and scope. Both quotes should measure the same area and include the same upstands, trims, outlets and rooflights.
- Strip or overlay. A new covering laid over the old one without checking the deck is cheaper for a reason. See overlay or strip.
- System and build-up. The membrane, its thickness or number of layers, and the insulation type and thickness should all be named.
- Deck allowance. Look for a stated rate for any rotten boards found during strip-out.
- Building regulations. If the roof is over a heated room, the quote should say how the insulation upgrade and approval are handled. Our building regulations guide explains when this applies.
- Guarantees. Ask which guarantees you will receive in writing: workmanship, manufacturer material and any insurance-backed cover. They are separate documents, as our guarantees guide explains.
Our replacement and new-roof quotes are fixed and written after a free, no-obligation survey, the work is carried out by vetted roofing teams working under S&K, and every re-roof comes with a written workmanship guarantee. Start with the guide-price tool or book a survey.
More questions
How much does it cost to re-roof a flat garage roof?
A single garage of around 18 m² on a sound deck typically costs £1,500–£2,600 in torch-on felt, £1,600–£2,800 in EPDM or £1,800–£3,250 in GRP, including VAT. A rotten deck adds to that.
Why does a small flat roof cost so much per square metre?
Set-up, travel, waste and detailing cost much the same on a small roof as on a larger one, so they make up a bigger share of the price. That is why a full re-roof carries a minimum charge of £750–£1,250.
Is the cheapest flat roof system the best value?
Not always. Torch-on felt usually has the lowest upfront price, but EPDM and GRP typically last longer, so the cost per year of service can be similar or lower.
Do your guide prices include VAT?
Yes. All guide prices include VAT at 20% and use a West Midlands baseline. The fixed price for your roof is confirmed in writing after a free survey.