A flat roof price is usually quoted in pounds per square metre, and that single figure hides a lot. It normally covers the membrane and the labour to lay it. The scaffold, the strip-out, the insulation, any repairs to the deck underneath and the metal trims around the edge all add to the job, and on some roofs they add up to as much as the membrane itself.
This guide sets out the ranges published by national cost guides, mainly MyBuilder's flat roof guide (updated August 2026), so you can see the spread before anyone visits. They are national figures, not Supreme Roofing prices. Our quote follows a survey and covers the whole job. For the wider picture of how we work on this type of roof, start at our flat roofing page.
Per square metre, material by material
MyBuilder's flat roof cost guide gives a separate range for each covering. The table sets those beside a typical life for the same material. The lives in the third column come from other guides (Less and GreenSpec), so the columns have different authors and are rough companions, not a matched pair.
| Covering | Typical price per m² | Typical life |
|---|---|---|
| Bitumen felt | £70 to £100 | 10 to 20 years |
| EPDM rubber | £90 to £130 | 20 to 30 years or more |
| GRP fibreglass | £95 to £150 | 25 to 40 years |
| PVC single-ply | £95 to £140 | 20 to 30 years |
| Lead | £150 to £200 and above | 50 to 100 years |
Prices: MyBuilder flat roof cost guide, updated 21 August 2026. Lives: Less (updated March 2026) for felt, GRP and lead; GreenSpec for EPDM and PVC. A lifespan is a typical range that depends on workmanship, exposure and upkeep. It is never a promise.
Why the ranges are so wide
Each band is between £30 and £55 across, and the reasons sit in the job, not the material. A felt roof built in three layers costs more than one built in two. A GRP roof with a decorative top coat costs more than a plain finish. An EPDM sheet that can be laid in one piece needs less labour than a roof cut up by rooflights and upstands. When two quotes for the same material differ, the cause is nearly always in the specification, so compare what each covers before the totals.
Where lead fits
Lead sits in its own band because the metal itself is expensive and the work is slow. On a main flat roof it is rare, and you are more likely to meet it as flashings, dormer cheeks and small decorative roofs. Our comparison of flat roof materials covers where each covering earns its place.
From a rate to a whole roof
A rate per square metre only becomes useful when it is multiplied by the area. Take a 20 m² extension roof, roughly a 5 m by 4 m room. At the published EPDM range of £90 to £130 per m², the covering and its labour come to £1,800 to £2,600. The same area in felt, at £70 to £100, is £1,400 to £2,000. This is plain arithmetic on national rates, not a Supreme price, and it leaves out everything in the sections below.
For a whole flat roof replacement, MyBuilder's guide quotes £2,800 to £7,500. Its garage roof guide is more specific about small buildings: £700 to £1,000 for one flat single garage roof, and £900 to £1,400 for a double. These are the same kind of roof, only smaller, and the figures show how little of the price is the membrane itself.
The fixed costs of a small job
Getting to the roof, setting up safe edge protection, taking the old covering away and clearing the site cost much the same whether the roof is 8 m² or 40 m². Spread across a small area they make each square metre dearer. This is why a bay window roof or a porch can look expensive next to a figure quoted for a large extension. It is not an error in the quote.
The labour figures
MyBuilder's re-roofing guide gives a roofer's day rate of £250 to £300. A flat roof of modest size is often a matter of days rather than weeks, but the covering needs dry conditions to be laid properly, so the programme is set by the weather as well as the area. The written quote allows for that and names it, instead of leaving it to turn up on the day.
Insulation: the line that varies most
Stripping a flat roof back and fitting a new waterproof membrane falls under Part L as the renovation of a thermal element of the Building Regulations. Approved Document L sets the target at a U-value of 0.16 W/(m²·K) when more than 50% of the surface is renovated, and 0.15 for a new roof element. Those targets mean new insulation is nearly always part of a full replacement. Our guide to flat roof Building Regulations sets out the rules in full.
Why the price moves
No national guide we have found publishes a separate price for the insulation layer, so we do not quote one. What we can say is what drives it. The thicker the board, the more it costs. A tapered scheme, where the boards themselves are cut to create the falls, costs more than flat boards laid on a deck that already slopes. And where the roof has to meet a door threshold or an existing window cill, a thicker build-up may need the upstand raised or the door adjusted. That is a survey item, and it is better found before the order goes in than after.
VAT on the insulation
Roofing work is normally standard-rated for VAT, but the insulation is treated differently: VAT Notice 708/6 zero-rates the fitting of insulation to a home's roof or loft until 31 March 2027. We do not advise on how VAT applies to a mixed job. Your quote shows VAT, and your accountant or HMRC can confirm how it applies to yours.
The way the layers are arranged matters as much as the thickness, and a warm roof, a cold roof and an inverted roof carry different costs and different risks. Our explanation of warm, cold and inverted flat roofs takes each in turn.
The deck under the old covering
Nobody can see the deck until the old covering comes off, and it is the largest unknown on a flat roof price. The deck is the board layer the membrane sits on, usually plywood, OSB or timber boards on joists. Where the old roof has leaked slowly, the boards below the leak can be soft or stained, and the joists beneath may be affected too.
What we can tell from the survey
Looking from the roof edge and from the room below tells us a good deal. We look for sagging, for staining on the ceiling, for ponding (standing water) on the old covering, and for soft spots underfoot. We take photographs of your roof and show them to you. Where a moisture reading or a small opening is needed, the quote states that and gives the reason.
How it appears in the quote
Because the true condition is only confirmed on strip-out, we tell you the basis on which any deck repair is charged, instead of folding an unseen allowance into the total. If the deck is sound, that line does not apply. If boards need replacing, you have already seen how they are priced. Approved Document A, which deals with structure, also notes that a roof which is overstressed or deflecting enough to cause ponding needs strengthening, so a sagging deck is a structural matter and not only a waterproofing one.
Nothing here changes the covering rate in the table. It is the reason the covering rate is only part of the answer.
Access, scaffold and the edges of the roof
Scaffold is the first extra most owners meet. MyBuilder's re-roofing guide puts scaffold at about £1,125 for a full house roof, and Checkatrade's roof replacement guide (updated October 2026) gives a range of £700 to £1,300. MyBuilder's guttering guide gives a per-area figure of £20 to £40 per m². A single-storey extension needs less than a full house, and a low roof reached from a safe, flat patio may need only edge protection. Which one applies is settled at the survey.
Stroud access
Our valley-side planning is built into the quote. A house on a steep lane, a terrace with no rear access or a roof that can only be reached through the house all change how materials arrive and how waste leaves. Rolls of membrane and sheets of insulation are awkward to carry through a hall, and a skip that cannot stand near the house means a longer carry. These costs are named on the written quote after the survey.
Waste
MyBuilder puts disposal of old roofing at £100 to £1,000, a wide range because old felt, insulation and decking weigh a lot. Clearing and removal is part of our quote.
Edges, upstands and trims
The perimeter of a flat roof is where most of the detail sits. Drip edges, kerbs around rooflights, upstands against a wall, and flashings in lead or a lead substitute are all priced by the metre or by the item. Checkatrade gives lead flashing repairs at £50 to £70 per metre and stepped flashing at £80 to £120 per metre (Code 5, excluding VAT). Those are repair rates, but they show the scale: a long wall abutment is a real cost on its own.
Reading a flat roof quote
A written quote that carries a single total for the roof tells you very little. Ours, sent after the survey, covers the whole job, which lets you set it against another firm's price.
| Line | What it should tell you |
|---|---|
| Scaffold or access | Whether it is a full scaffold or edge protection, and who removes it |
| Strip and waste | What comes off, and how it is taken away |
| Deck repair | Included or on a stated basis if the boards are found unsound |
| Insulation | Type, thickness and the U-value it is meant to reach |
| Membrane and labour | The named system, its thickness or layers, and its guarantee terms |
| Trims and details | Edges, upstands, outlets and rooflights, each counted |
What to compare
Two quotes for 'a new EPDM roof' can differ by thousands without either being wrong, because one includes new insulation and a tapered scheme and the other relays the old board. Ask each firm what is under the membrane, not just what is on top. Our page on repairing or replacing a flat roof is the place to start if you have not yet decided whether a whole new roof is needed.
Give a price a fair test: does it name the insulation, the deck allowance and the trims? If it does not, it is a covering price, not a roof price.
We back our work with a 10-year workmanship guarantee in writing. A manufacturer's product guarantee is a separate thing, and the quote should say which one it is describing.