Flat Roof Replacement Cost UK 2026: Prices by Size and Material

A 5 square metre porch canopy and a 70 square metre extension are both flat roofs. That is why the published averages for this job range from £2,400 to £8,000 and why none of them tells you much about your own.

The flat roof replacement cost that matters is the one you can work out yourself from two numbers: how many square metres you have, and which material is going on. Everything else is detail.

What's New in Flat Roof Costs for 2026

EPDM rubber has become the default choice on most homes, and the reason is lifespan rather than price. At £50 to £90 per square metre it is not the cheapest option. Felt still is. But EPDM is quoted at 30 to 50 years against 15 to 20 for torch-on felt, and that arithmetic has become the standard sales conversation in 2026 rather than an upsell.

Minimum job charges are also being stated openly. Many contractors now apply a floor of £300 to £500 on small flat roofs, which stops the smallest jobs being priced purely per square metre. If you have a porch canopy, that floor is probably what you will pay.

The headline ranges have not moved much. Checkatrade, MyBuilder and Fix My Roof all put a typical residential flat roof at £2,800 to £7,500 in 2026, the same band as the year before.

What Flat Roof Replacement Cost Averages in 2026

Five published averages, all UK, all 2026:

• £2,400 according to MyJobQuote
• £2,500 according to MyJobQuote's separate cost page
• £75 per square metre as an average rate according to Fix My Roof and MyBuilder
• £8,000 according to the Federation of Master Builders

The FMB figure is more than three times MyJobQuote's. That looks like an error until you look at what each is counting. MyJobQuote's average is dominated by garages and porches. The FMB's size table starts at 20 square metres and runs to 70, so it is averaging extensions.

Both are honest numbers about different jobs that share a name.

The ranges are more useful. Bernard Andrews Roofing gives £1,500 to £7,500 for most UK homes. MyJobQuote gives £1,500 to £6,000. Checkatrade, MyBuilder and Fix My Roof all give £2,800 to £7,500.

Take £1,500 to £7,500 as the working band, and understand which end you are at by measuring the roof. Anything quoted below £800 is almost certainly a patch rather than a replacement, and anything above £10,000 means either a very large area or a deck that has to be rebuilt underneath.

Flat Roof Replacement Cost by Size: £800 to £12,600

Priced by area, the numbers become predictable in a way the averages never are.

• Porch or bay window, 5 to 8 square metres: £800 to £1,500
• Garage, about 15 square metres: £1,200 to £2,400
• Small porch or garage, 20 square metres: £2,800 to £3,600
• Rear extension, 20 to 25 square metres: £1,800 to £3,500
• Small extension, 30 square metres: £4,200 to £5,400
• Large extension, 35 to 45 square metres: £3,000 to £6,500
• Medium extension, 50 square metres: £7,000 to £9,000
• Larger extension or garage block, 70 square metres: £9,800 to £12,600

The two sources behind that list do not agree perfectly. A 20 square metre roof appears at both £1,800 and £3,600 depending on who is quoting and what material they assume. Read the overlap rather than any single line, and use the material rates below to narrow it.

Per square metre, the whole job sits between £45 and £130 across every source. Fix My Roof and MyBuilder both settle on £75 per square metre as a national average, and that is a reasonable number to sanity-check a quote against. Multiply your area by £75 and you should be somewhere near the middle of a fair range.

Garage Flat Roof Cost: £1,000 to £2,700

This is the most common flat roof job in the country, so it is worth pricing on its own.

• Single garage: £1,000 to £2,200
• Double garage: £1,600 to £4,500
• Garage at about 15 square metres: £1,200 to £2,400

Split by material on a single garage, the choice is worth about £1,000:

• Felt garage roof: £1,200 to £1,800
• Rubber garage roof: £1,650 to £2,400
• Fibreglass garage roof: £1,800 to £2,700

A new EPDM roof on a 25 square metre garage or extension runs £1,500 to £3,500 and takes 2 to 3 days.

On a garage the material decision is easier than on a house, because nobody is looking at it and the roof is usually simple. That argues for picking on lifespan. The £450 or so between felt and rubber buys you an extra 15 years at the low end of the published lifespans.

Felt vs EPDM vs GRP: Price and Lifespan

Installed prices per square metre, with the working life each is quoted at:

• Torch-on or built-up felt: £40 to £70 per square metre, lasting 15 to 20 years
• EPDM rubber: £50 to £90 per square metre, lasting 30 to 50 years
• GRP fibreglass: £80 to £130 per square metre, lasting 25 to 40 years
• Single-ply PVC: £55 to £85 per square metre

MyJobQuote quotes higher installed rates across the board: £80 to £120 for felt, £110 to £160 for rubber and £120 to £180 for fibreglass. The ordering holds even where the numbers differ.

Now do the sum that the per-square-metre price hides. On a 20 square metre garage:

• Felt at £55 per square metre is about £1,100, over 17 years, so roughly £65 a year
• EPDM at £70 per square metre is about £1,400, over 40 years, so roughly £35 a year

The cheaper roof costs nearly twice as much per year. That is the case for EPDM on most homes, and it is why it has become the default.

GRP earns its premium in a narrower set of situations. It is rigid rather than a membrane, so it suits balconies, walkable areas and roofs with awkward shapes and lots of upstands. On a plain rectangular garage it is money spent on a property nobody uses.

Felt still makes sense for a genuinely short-term fix, or where the structure underneath is coming down within a few years.

Full Price by Material and Roof Size

Fix My Roof publishes the clearest breakdown of the four common systems across three roof sizes. Small here means a porch or single garage, medium a typical extension, and large a big extension or garage block.

• Felt, built-up: £40 to £60 per square metre. Small £600 to £900. Medium £2,800 to £3,600. Large £4,000 to £6,000.
• EPDM rubber: £50 to £80 per square metre. Small £750 to £1,200. Medium £3,000 to £4,800. Large £5,000 to £8,000.
• Single-ply PVC: £55 to £85 per square metre. Small £825 to £1,275. Medium £3,300 to £5,100. Large £5,500 to £8,500.
• GRP fibreglass: £60 to £90 per square metre. Small £900 to £1,350. Medium £3,600 to £5,400. Large £6,000 to £9,000.

Two worked examples make the pattern concrete. A 20 square metre EPDM replacement comes in at £2,800 to £3,600. A 50 square metre project sits nearer £7,000 to £9,000.

Single-ply PVC is the option most homeowners never hear about. It prices between EPDM and GRP, comes in wide sheets that suit large simple roofs, and is more common on commercial buildings than houses. It is worth asking about on anything above 40 square metres.

The gap between the cheapest and dearest system on a large roof is about £3,000. On a small one it is closer to £450. That is why material choice deserves more thought on an extension than on a porch: the same decision costs seven times as much.

What the Deck Underneath Adds: £25 a Board

The covering gets all the attention, but a flat roof is a timber deck with a waterproof layer on top. When a flat roof fails, water usually gets into the deck long before anyone notices the ceiling.

Nobody can price this before the old covering comes off, which is exactly why it belongs in your quote as a rate rather than a guess.

Decking. OSB board runs around £25 a sheet depending on size and thickness, and typical decking prices start from £25 per square metre. A garage roof might need two or three boards replaced, or the whole deck if water has been sitting in it.

Vapour control layer. A VCL sheet costs about £27 for a 25 metre roll. It sits under the insulation and stops moisture from inside the building condensing in the roof build-up. Leaving it out is a false saving that shows up as damp decking a few years later.

Insulation. If you are replacing more than half the roof, building regulations generally expect the new roof to meet current insulation standards. That usually means a warm deck build-up, with insulation above the timber rather than between the joists. It adds cost and it adds height, which matters where the roof meets a door threshold or a window.

Ask the roofer three questions before you sign: what happens if the deck is wet, what the rate per board is, and whether the quote assumes a warm deck. A quote that answers all three is comparable. One that says "replace flat roof" is not.

Why Small Flat Roofs Cost More per Square Metre

A 5 square metre porch does not cost a fifth of a 25 square metre extension, and people are often caught out by this.

The reason is that a large part of any flat roof job is fixed. The roofer travels to you, sets up, strips the old covering, checks the deck, and comes back to clear up. That happens whether the roof is 5 square metres or 50. Materials scale with area. Almost nothing else does.

This is why minimum job charges of £300 to £500 exist. Below a certain size, per-square-metre pricing stops covering the day.

Two things follow from it.

Bundle small jobs. If the porch and the garage both need doing, one visit is far cheaper than two. The same applies to gutter and fascia work while the roofer is there.

Do not read a high per-square-metre rate on a small roof as a rip-off. A £1,200 job on 8 square metres is £150 per square metre, well above every published rate on this page, and still perfectly fair.

What Roofers Charge by Region: £130 to £380 a Day

Labour rates vary more by geography than most people expect:

• National average: £19 to £35 an hour, or £150 to £270 a day
• London: £28 to £50 an hour, or £220 to £380 a day
• South East: £24 to £42 an hour, or £190 to £330 a day
• Midlands: £18 to £32 an hour, or £145 to £260 a day
• Scotland: £18 to £30 an hour, or £140 to £250 a day
• North of England: £16 to £28 an hour, or £130 to £240 a day
• Wales: £16 to £28 an hour, or £130 to £230 a day

The top of the London range is nearly three times the bottom of the Welsh one. On a three-day garage roof that is a difference of about £450 in labour alone, on identical work.

The same pattern shows in finished job prices. A flat roof replacement costing £4,000 in most of the country reaches £5,000 to £5,200 in zone 1 and 2 London postcodes.

If you are comparing your quote against a national average, adjust for where you live before deciding it looks high.