Costs · updated July 2026
Flat roof cost in Wisbech
Flat roof cost in Wisbech by system, per square metre and per job, how long each one really lasts, and why an exposed site is hardest on the edges.
Guide ranges, not quotes
Every number here is a researched guide range for the Wisbech area as at July 2026, including VAT. None of it is an offer or a quotation and no roofing firm is bound by it.
This site is not a roofing contractor. It is a free quote-comparison service operated by Expert Roofers, so nothing here gains from talking a price up. The firms we introduce you to will price your actual roof.
A flat roof is the one part of a house where the cheapest and dearest quotes are frequently for genuinely different products with genuinely different lifespans. Comparing totals tells you little. Comparing what each costs per year of life tells you almost everything, and there is a table below that does exactly that. Five systems cover nearly all domestic work here, and they are not interchangeable.
- Torch-on felt. Bitumen membrane heat bonded on site in layers. The cheapest proper system and still the usual thing on a garage.
- EPDM rubber. A single sheet of synthetic rubber bonded down, usually with no joins at all on a domestic roof.
- GRP fibreglass. Resin and matting laid wet and cured into one rigid shell. Walkable, but temperature dependent to lay and it cracks on a deck that moves.
- Single ply. A factory-made PVC or TPO membrane, hot air welded at the seams. Comes into its own on a larger simple roof.
- Liquid applied resin. Cold applied, so it follows complicated shapes. Useful where there are penetrations and upstands everywhere.
Flat roof cost per square metre by system
| System | Guide rate per m² | Realistic life | Best suited to |
|---|---|---|---|
| Torch-on felt, three layer | £70 to £110 | 15 to 20 years | Garages, outbuildings and budget-limited re-covers |
| EPDM rubber, single sheet | £85 to £130 | 25 to 35 years | Garages, extensions and simple dormers |
| GRP fibreglass | £95 to £150 | 20 to 30 years | Balconies, roofs that get walked on, rigid decks |
| Single ply, PVC or TPO | £110 to £170 | 25 to 35 years | Larger extensions, above roughly 35 m² |
| Liquid applied resin | £110 to £180 | 20 to 25 years | Penetrations, kerbs, upstands and awkward shapes |
| Warm deck insulation, added to any of the above | £45 to £85 | Matches the covering | Any flat roof over a heated room |
Small roofs run above the top of these bands, because set-up, edge trims, the skip and the travel do not shrink with the area. The whole-job figures below allow for that and are the ones to hold a quote against. Manufacturer life claims are longer than these figures. These are what the systems realistically achieve on domestic roofs here.
Typical whole-job flat roof prices
| Roof | Approximate area | Torch-on felt | EPDM | GRP fibreglass |
|---|---|---|---|---|
| Porch or small canopy | 4 to 7 m² | £700 to £1,200 | £850 to £1,400 | £950 to £1,600 |
| Flat roof dormer | 6 to 12 m² | £1,100 to £1,900 | £1,300 to £2,200 | £1,400 to £2,400 |
| Single garage | 15 to 18 m² | £1,300 to £1,800 | £1,600 to £2,100 | £1,700 to £2,300 |
| Small extension or kitchen | 12 to 20 m² | £1,400 to £2,000 | £1,700 to £2,400 | £2,200 to £3,000 |
| Double garage | 30 to 36 m² | £2,000 to £2,900 | £2,300 to £3,300 | £2,500 to £3,600 |
| Large extension | 25 to 35 m² | £2,200 to £3,000 | £2,500 to £3,300 | £2,900 to £3,600 |
Where the deck is not sound, add £500 to £900 on a garage or £600 to £900 on an extension or dormer, which keeps a garage in EPDM and an extension in fibreglass inside the ranges on the roofing costs hub. Where the deck, the falls and the insulation all have to go, you are building a new flat roof rather than re-covering one, and it should be quoted as such instead of measured against these figures. Scaffold is rarely needed at ground level but is normally required on a dormer, at £450 to £900 for one elevation. Above roughly 35 m² you are into single ply territory.
Cost per year of life, the only honest comparison
Nobody buys a flat roof once. You buy it again every time it fails, so the number that matters is what it costs per year until it needs doing again. Worked on a single garage of about 16 square metres at the middle of each range above, the ranking flips.
| System | Mid-range job price | Realistic life | Cost per year |
|---|---|---|---|
| Torch-on felt, three layer | £1,550 | 18 years | About £86 |
| EPDM rubber | £1,850 | 30 years | About £62 |
| GRP fibreglass | £2,000 | 25 years | About £80 |
| Single ply | £2,250 | 30 years | About £75 |
| Liquid applied resin | £2,300 | 22 years | About £105 |
Cheapest per year is not automatically right for your roof. GRP costs more per year than EPDM but it is walkable. Felt costs the most per year and is still the sensible answer if you are selling in three years. Single ply gets cheaper per square metre as the roof grows, so on a 60 m² roof this table looks very different. On an exposed site none of these lives out its stated span if the perimeter fixing and the edge trims were skimped, which is why the next two sections matter more here than the choice of membrane.
The deck, the falls, and what a cheap re-cover hides
Almost every early failure traces back to something under the membrane rather than to the membrane itself. Two questions settle most of it before you accept a quote.
Is the deck sound
If the boards are soft, springy or stained, they go back down under a new covering only if somebody is cutting a corner. A membrane laid over a wet deck will fail, and the guarantee will not survive the argument about whose fault that was.
Are the falls right
A flat roof is not flat. It needs a designed fall so that water leaves, commonly built at around 1 in 40 so that after deflection there is still at least 1 in 80 left. Standing water, which roofers call ponding, is the most common reason a flat roof dies young, and it is nearly always a design fault rather than a product fault.
Correcting a fall means firring strips on a new deck, which is why the cheapest quote, the one that re-covers straight over the existing boards, is often the most expensive decision on this page.
| Work | Guide cost | Notes |
|---|---|---|
| New 18mm WBP plywood deck | £35 to £55 per m² | The usual specification under EPDM, GRP and single ply |
| New OSB3 deck | £28 to £45 per m² | Cheaper, accepted under some systems but not all |
| Firring strips to create or correct a fall | £12 to £25 per m² | The fix for ponding, and it needs a new deck |
| Replace rotten joists | £45 to £90 per metre | Cannot be priced until the deck is off |
| Complete new deck, single garage | £500 to £900 | Roughly 15 to 18 m², including disposal |
| Complete new deck, extension or dormer | £600 to £900 | Roughly 12 to 25 m², including disposal |
| New rainwater outlet and connection | £150 to £350 | Often the cheapest thing that prevents a failure |
| Upgraded edge trim and perimeter fixing | £8 to £18 per linear metre | The exposure line. Corners and edges take the uplift |
| Mechanically fixed rather than bonded insulation | £6 to £14 per m² | Worth asking about on any open, unsheltered site |
A good quote gives you a rate and an allowance rather than silence, and a phone call before anything beyond that allowance is done.
Insulation and the building regulations
This catches people out, and it is not optional. Under the building regulations, replacing more than half the surface area of a flat roof over a heated room counts as renovating a thermal element, so the insulation normally has to be brought up to current standards. The figure usually applied is a U-value of 0.18 W/m²K. Building control will confirm what applies to your roof, and that conversation belongs before you accept a quote rather than after.
In practice it means insulation boards above the deck, typically 120 to 150mm of rigid PIR, which is what a warm deck is. Budget £45 to £85 per square metre on top of the covering, so roughly £550 to £1,400 on a small extension. It has physical consequences as well as financial ones.
- The roof gets 120 to 150mm taller, so upstands, abutment flashings and any door threshold onto the roof all have to be re-set.
- A window or door head sitting close to the roof line can become tight. Far cheaper to discover now than halfway through the job.
- A cold deck, with insulation between the joists and a ventilated void above, is the old approach. It is harder to get right, needs continuous cross ventilation, and is why a lot of 1980s flat roofs rotted from the inside out.
- A detached unheated garage is not a thermal element, so none of this applies to it. An integral garage with a heated room against it may be a different matter.
Allow for a building control fee too, separate from the roofer's quote and normally a few hundred pounds. Ask who is notifying building control and get the answer in writing, because a flat roof done without it becomes somebody's problem at the point of sale. If the roof is visible from the street and the property is listed or inside one of Fenland District Council's conservation areas, the appearance question arises too, and the council gives inserting dormers as one of its own examples of the minor alterations it controls. See listed buildings and conservation areas before you commit to anything.
Why flat roofs fail early here
Flat roofs have a bad reputation and they mostly earned it, but they earned it in four specific ways. Each is avoidable at the quoting stage, and on an open site the third and fourth do more damage than they would twenty miles inland.
1. The falls were never right
Water that cannot leave sits there, and standing water shortens every system on this page. If your roof ponds, a re-cover that does not touch the falls buys the same failure again on a newer membrane. Ask what the roofer intends to do about the falls, and treat no answer as an answer.
2. It failed at an edge, not in the middle
Very few flat roofs fail in the field. They fail where the membrane meets something else: an upstand, a parapet, a rooflight kerb, a soil pipe, the outlet. It should be dressed up at least 150mm at every upstand and terminated into a proper flashing or chased into the brickwork, not stuck to the wall and left to peel.
3. Wind scour, which is the local one
On flat, open fen with a tidal river through it and nothing upwind, the wind does not simply blow across a flat roof, it lifts at the perimeter and the corners. That is where fixings pull, where an under-specified edge trim lets go and where a bonded insulation board starts to move. It is why the perimeter fixing line in the deck table is worth asking about, and why a roof that lasted twenty-five years in a sheltered close might not manage it on an open plot towards Walsoken or Guyhirn. A firm that raises edge and corner zones unprompted has thought about your roof.
4. The weather it went on in
Fibreglass is the one to watch. The resin cures by chemical reaction and the cure is temperature dependent, so it should not be laid in cold or damp conditions. Combine a short winter working window with a site where the wind rarely stops and a GRP roof rushed on in November is a real risk. A firm that would rather wait a fortnight knows what it is doing.
For the work itself rather than the price see flat roofing, and for pitched work see roof repairs. Every other job is priced on the roofing costs hub. Read how to choose a roofer, then compare quotes from firms that cover your postcode.
Frequently asked questions
For a simple domestic roof with few penetrations, EPDM is the default on cost per year of life. GRP wins where the roof gets walked on. Single ply wins once the roof is large. Felt wins on price today and on nothing else.
A single garage takes one to two days to re-cover and a small extension two to three, plus a day if the deck is being replaced.
Sometimes, with felt over felt, and it is usually a false economy. You are adding weight, hiding whatever is wrong underneath and guaranteeing the falls stay exactly as bad as they were.
Most manufacturers will not warrant their system over an existing covering, which tells you what they think of the idea.
If you are replacing more than half the surface of a flat roof over a heated room, yes, because that counts as renovating a thermal element and triggers an insulation upgrade. Structural work to the deck or the joists is notifiable too. A detached unheated garage generally is not.
If in doubt, ask building control before the work rather than after it. Fixing this at the point of sale is expensive and slow.
Usually one of four things is missing: deck replacement, the insulation upgrade, correcting the falls, or proper edge trims and upstand detailing. Occasionally it is a cheaper system quoted against a dearer one without saying so.
Ask each firm to name the system, the deck specification, the insulation, the perimeter fixing and the guarantee. Compared like for like, honest quotes cluster much closer together than people expect.
It shortens a badly detailed one. The membrane in the middle of the roof is not what is at risk. What is at risk is the perimeter: the edge trim, the fixings in the corner zones and, on a warm deck, whether the insulation is bonded or mechanically fixed.
That is why a quote here should say something about the edges. A specification that only names the membrane has answered the easy half of the question.
Two different things get called a guarantee. The manufacturer's product warranty covers the membrane and is often long, but it only pays for material. The installer's workmanship guarantee covers the part that actually fails, because on a flat roof nearly every failure is workmanship or design.
Ask for both in writing, and ask whether the workmanship guarantee is insurance backed.
A fall that is too shallow, a fall running the wrong way, a deck that has deflected between the joists, or an outlet that is not at the lowest point. It is almost never the membrane's fault.
Puddles that clear within a day or two are normal. Water still sitting there in dry weather is not, and it is the single best predictor of an early failure.
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