Written by Andrew, Lead Roofer
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CORC Certified
Public Liability Insured
Emergency Roof Repairs 24/7
Most flat roof repairs cost £150 to £500 in 2026. London prices for felt, EPDM and GRP leaks, outlets and flashing, plus when to stop patching.
Flat roof repair costs £150 to £500 for most leaks and patches in the UK in 2026, rising to £500 to £1,200 to re-cover a damaged section of up to 10m². The final price depends on the roof covering, what is actually causing the leak and how the roofer gets onto the roof. London prices run 15 to 30 per cent above the national figures because access, parking and labour all cost more in the capital.
Flat roofs cover most of the rear extensions, garages, dormers, bay windows and balconies in London, and a flat roof leak usually announces itself as a brown stain on a kitchen ceiling after the first heavy rain of autumn. Prices in this guide are UK prices in pounds, include labour and materials, and show London figures separately.
This guide covers flat roof repair costs by repair and by material, why repairs are priced per job rather than per square metre, what a proper leak repair involves, why patches fail on badly drained roofs, London access costs, emergency repairs, when to stop patching and when building regulations apply.
Flat roof repair costs in the UK fall into three bands. Small repairs such as a felt patch, an EPDM seam or a resealed flashing cost £150 to £500. Re-covering a damaged section of up to 10m² costs £500 to £1,200. Larger sections cost £1,000 to £2,500, and at that point a full flat roof replacement is worth pricing alongside the repair.
| Flat roof repair | Typical UK cost | Typical London cost |
|---|---|---|
| Leak tracing and inspection only | £150 to £300 | £170 to £390 |
| Patch or seam repair (felt, EPDM or GRP) | £150 to £500 | £170 to £650 |
| Flashing or outlet repair | £150 to £500 | £170 to £650 |
| Re-covering a section up to 10m² | £500 to £1,200 | £580 to £1,550 |
| Re-covering a larger section | £1,000 to £2,500 | £1,150 to £3,250 |
| Full flat roof replacement, for comparison | £1,500 to £7,500 | Priced by size and material |
Flat roof repair prices sit alongside tile, chimney and leadwork repairs in the roof repair cost guide, which uses the same figures for felt, EPDM and GRP repairs.
Flat roof repair costs depend more on the type of fault than on the size of the roof. A split in the felt over a garage and a failed flashing along the back wall of a kitchen extension can leave the same stain on the ceiling, but the two repairs use different materials, take different amounts of time and come with different prices.
| Type of flat roof repair | Typical UK cost | Typical London cost |
|---|---|---|
| Leak tracing and inspection only | £150 to £300 | £170 to £390 |
| Felt patch (blister or split) | £150 to £350 | £170 to £460 |
| EPDM seam or edge repair | £200 to £400 | £230 to £520 |
| GRP crack repair | £250 to £500 | £290 to £650 |
| Liquid coating over a small area | £200 to £450 | £230 to £580 |
| Resealing flashing where the roof meets a wall | £150 to £350 | £170 to £460 |
| Replacing lead flashing along a wall (3m to 5m) | £400 to £800 | £460 to £1,050 |
| Clearing a blocked outlet | £150 to £250 | £170 to £320 |
| Replacing or resealing an outlet | £250 to £500 | £290 to £650 |
| Resealing a rooflight upstand | £250 to £500 | £290 to £650 |
| Fixing localised ponding | £500 to £1,500 | £580 to £1,950 |
| Re-covering a section up to 10m² | £500 to £1,200 | £580 to £1,550 |
London flat roof repair prices in the table apply a 15 to 30 per cent London premium to the UK figures. The London premium pays for parking, slower travel between jobs and London roofer day rates of £250 to £350.
Repairs to the details of a flat roof, such as flashings, outlets and rooflight upstands, cost more than a patch on open membrane because each detail has to be cut back, dried, rebuilt and sealed into the roof covering around it.
The covering on a flat roof decides how a repair is carried out and how long the repair lasts. Mixing materials is one of the commonest reasons a flat roof repair fails, because bitumen, rubber and polyester resin don’t bond reliably to one another.
| Roof covering | Typical repair | Typical UK cost | Typical repair life |
|---|---|---|---|
| Torch-on felt | Patch over a blister or split | £150 to £350 | 3 to 7 years |
| EPDM rubber | Seam, edge or puncture repair | £200 to £400 | 10 to 15 years |
| GRP fibreglass | Crack repair with new resin and matting | £250 to £500 | Depends on the deck and laminate around it |
| Liquid coating | Small area over a sound, dry surface | £200 to £450 | Depends on the coating and the surface below |
Felt roof repair is the most common flat roof repair in London, because torch-on felt still covers a large share of older extensions, garages and dormers. A felt roof repair involves cutting out the blister or split, drying and cleaning the area, and torching a new cap sheet patch over the damage with a generous overlap onto sound felt. Felt patches typically last 3 to 7 years. The patch itself often holds for longer, but the felt around it keeps ageing, so the next split tends to appear a short distance away.
Garages and outbuildings are sometimes covered in nailed shed felt rather than torch-on felt. A garage roof in shed felt that is splitting in several places is usually cheaper to re-cover than to keep patching.
EPDM rubber roofs usually fail at the seams, at the edge trims and wherever the membrane has been punctured by foot traffic or a fallen branch. A rubber roof repair uses an EPDM patch or seam tape bonded with a compatible primer, and a well-made EPDM seam repair typically lasts 10 to 15 years. Bitumen products shouldn’t go anywhere near an EPDM roof, because bitumen doesn’t bond to the rubber and the solvents in some bitumen sealants attack the membrane.
Fibreglass roof repair involves grinding back the cracked area, laying new resin and glass matting, and finishing with a fresh topcoat. GRP roofs crack most often at the joints between deck boards, around trims and at upstands, usually because the timber deck underneath has moved. A GRP repair needs a dry day and a mild temperature for the resin to cure, which makes fibreglass repairs harder to schedule in a London winter. The new topcoat rarely matches a faded GRP roof exactly, so the repair usually shows.
Liquid roof repair coatings are brushed or rolled on and cure into a continuous layer with no joints. A liquid coating works well on awkward details such as pipe penetrations and on small areas of sound, dry roof. A liquid coating brushed over a damp or failing felt roof can blister and lift within a season, and the coating hides the real condition of the roof underneath.
Flat roof repairs are priced per job because most of the cost of a small repair is fixed. Getting onto the roof, setting up ladders or a tower, parking, buying a minimum quantity of materials, cutting out and drying the damaged area and water-testing the finished repair cost much the same whether the damage covers half a square metre or two.
Some online cost guides and AI search answers quote flat roof repairs at £100 to £200 per square metre and then multiply that rate by the size of the roof, which turns a small repair into a bill of £1,000 or more. Per square metre pricing belongs to re-covering and replacement, where the area of the roof really does drive the cost. A single split in the felt over a garage costs £150 to £350 to patch, whatever the size of the garage.
Re-covering part of a flat roof costs more per square metre than replacing the whole roof. Re-covering a section of up to 10m² costs £500 to £1,200 because the new membrane has to be joined to the old roof along every edge, and each joint between new and old has to be sealed properly. The square metre rates in the flat roof replacement cost guide exclude stripping the old roof, skip hire and scaffolding, which are priced separately. A per square metre price for a single leak is often a sign that the job is really being priced as a partial re-cover, so ask the roofer to explain what the repair involves.
A leaking flat roof repair starts with finding where the water gets in, and that point is rarely directly above the stain. Water under a flat roof covering can track along the timber deck and the joists for a metre or two before it finds a way through the plasterboard. A stain in the middle of a kitchen ceiling can come from a flashing at the far edge of the roof.
Flat roof leaks on London extensions usually start at the details rather than in the open membrane. Most leaks begin at the joint where an extension roof meets the back wall of the house, at the outlets and rooflight upstands, along the edge trims or under balcony door thresholds. Every one of these details relies on a seal that has to cope with movement, sun and standing water for years.
A roofer repairing a flat roof leak properly checks the membrane and every detail on the roof, looks for soft or spongy areas that point to a wet deck and, where the source isn’t obvious, water-tests sections of the roof one at a time. The repair then matches the fault: a patch for a split, new flashing for a failed wall joint, a resealed or replaced outlet for a leaking drain. The flat roofing page explains how Bernard Andrews Roofing handles flat roof leak repairs across London.
Ponding is the term for water still lying on a flat roof 48 hours after rain, and ponding is one of the main reasons a flat roof patch fails. A patch sitting in standing water for days at a time never dries out, collects silt and wears out far faster than a patch on a well-drained part of the roof.
Flat roof drainage depends on the fall, the slight slope that carries rainwater to the outlets or the gutter. The British Standard for flat roofs, BS 6229:2025, was revised in December 2025 and calls for a finished fall of at least 1:80 on most flat roofs, along with an emergency overflow wherever a roof drains through a single outlet. Plenty of older London extensions and balconies were built with too little fall and one small outlet, so ponding returns however many times the surface is patched.
Flat roof outlets cause a large share of drainage problems. A flat roof outlet blocked by leaves and moss backs water up across the roof and against the upstands, and a balcony with a single outlet can flood within minutes in a summer downpour. Clearing a blocked outlet costs £150 to £250 and replacing or resealing a leaking outlet costs £250 to £500. Fixing localised ponding properly, by re-forming the falls in the affected area or adding an outlet or overflow, costs £500 to £1,500.
A patch laid over a wet timber deck fails early because the deck can’t dry out. Once water has been getting in for a while, the timber deck and the insulation hold moisture, and sealing a new patch over damp boards locks the moisture in place. A deck that feels soft underfoot needs the wet boards replacing, at £25 to £35 per square metre for new decking, before any new covering will last.
Access is the biggest variable in London flat roof repair costs. A ground-floor kitchen extension on a Fulham or Clapham terrace can usually be reached with a ladder from the garden, while a second-floor dormer or a roof over a street-facing bay may need a tower or scaffolding before any repair can start.
| Roof location | Usual access | Typical access cost on top of the repair |
|---|---|---|
| Garage or single-storey rear extension | Ladder | Usually included in the repair price |
| First-floor extension, bay or balcony | Tower | £250 to £600 |
| Dormer or flat roof above first floor | Scaffolding | £400 to £1,200 |
London council charges add to the bill when scaffolding, a skip or a van needs space on the road. Parking bay suspensions in Kensington and Chelsea cost £82 per space per day for the first five days, or £408 to apply at short notice, according to the Royal Borough of Kensington and Chelsea. A building licence for scaffolding on the highway in Camden costs £464.80 for minor works plus a £785.56 deposit, according to Camden Council. Most flat roof repairs at the back of a house need neither, but a repair that needs scaffolding on the pavement or a skip on the road usually does.
Mid-terrace houses without side access add time as well, because ladders, materials and waste all go through the house and the floors need protecting. Larger period houses in Holland Park and Kensington often have flat roofs hidden behind parapets, with box gutters and outlets that nobody sees until water comes through a top-floor ceiling.
An emergency flat roof repair stops water coming in until a permanent repair can be carried out in daylight and dry weather. Emergency call-outs in London typically cost £150 to £250 during working hours, £200 to £350 in the evenings and at weekends, and £300 to £500 on bank holidays, before the cost of the repair itself.
| Emergency flat roof work | Typical London cost |
|---|---|
| Call-out, weekday working hours | £150 to £250 |
| Call-out, evenings and weekends | £200 to £350 |
| Call-out, bank holidays | £300 to £500 |
| Temporary seal with liquid or repair tape | £150 to £300 |
| Tarpaulin over an area up to 5m² | £200 to £400 |
A temporary flat roof repair is a holding measure, not a fix. Emergency tape and liquid sealants rarely bond well to a wet roof, and most temporary repairs last weeks or a few months rather than years. A temporary repair is worth paying for when water is coming through a ceiling near light fittings or into a room in daily use, and the permanent repair should be booked as soon as the weather allows. The emergency roof repair guide covers what to do while waiting for a roofer.
Repairing a flat roof makes sense when the fault is isolated, the timber deck is dry and the roof covering has years of life left. A single split, one failed flashing or a blocked outlet on an otherwise sound roof should be repaired, not replaced.
Replacing a flat roof makes more sense when the evidence points to the whole roof rather than one detail. Leaks in different places over a few winters, a deck that feels spongy underfoot, ponding caused by falls built into the roof and a felt roof already 15 to 20 years old all suggest the roof has reached the end of its working life. Patching a flat roof that has already been patched two or three times is usually poor value.
The running total of repairs matters more than the price of any single patch. Three felt patch repairs at London prices of up to £460 each add up to almost £1,400 over a few winters, which is comparable to re-covering a 10m² section. Almost £1,400 is also more than half the £1,800 to £2,600 cost of replacing a typical 20m² kitchen extension roof in EPDM in Fulham or Clapham, according to the flat roof replacement cost guide.
The condition of the deck and the number of previous repairs are a better guide than the 25 per cent rule some guides use, because a cheap patch over a wet deck is poor value at any price.
Small flat roof repairs don’t normally need building regulations approval in England. Approved Document L treats replacing the waterproof membrane on a flat roof as renovating a thermal element, and the guidance only expects the whole roof to be brought up to current insulation standards when more than 50 per cent of the roof surface is renovated. A patch, a seam repair, a new flashing or a re-covered section well under half the roof doesn’t trigger that upgrade.
Re-covering more than half of a flat roof is a different matter. Once more than 50 per cent of the roof is renovated, the whole roof should be insulated to the U-value set out in the guidance, which usually means adding insulation above the deck as a warm roof. The 2026 edition of Approved Document L keeps the same 50 per cent threshold. Insulation laid on top raises the level of the roof, so upstands, door thresholds and flashings may need altering too, and the warm roof vs cold roof guide explains how the two constructions differ.
Roofers registered with CompetentRoofer, the competent person scheme run by the National Federation of Roofing Contractors, can self-certify larger flat roof refurbishments in England and Wales and issue a building regulations compliance certificate. Online answers claiming that every flat roof repair needs an insulation upgrade are wrong for small repairs.
Home insurance usually covers a leaking flat roof only when a storm caused the damage. The Financial Ombudsman Service says buildings insurance usually covers storm damage, but policies commonly exclude wear and tear and gradual damage, and a complaint is unlikely to succeed where the roof was already in bad condition and the storm only highlighted an existing problem. Photographs of the damage and a written report from the roofer help any claim.
A flat roof can be repaired without replacing it when the damage is limited to one area and the deck underneath is dry. Patch repairs, seam repairs, new flashings and outlet repairs fix the fault without stripping the roof, and most cost £150 to £500.
A flat roof keeps leaking after a repair when the patch went over the wrong spot, the deck underneath was already wet, water ponds over the repair or the repair used a material that doesn’t bond to the roof covering. Paying £150 to £300 to trace the real entry point saves paying for the same leak twice.
The best way to seal a leaking flat roof is to repair the covering with the same material: felt with torch-on felt, EPDM with EPDM primer and seam tape, and GRP with new resin and glass matting. Emergency tape and sealant only buy time until a proper repair.
A flat roof leak that is left soaks the timber deck and the insulation, stains and weakens the ceiling below and encourages mould. A long-running leak can rot the deck boards and the ends of the joists, which turns a £150 to £350 patch into a section re-cover or a full replacement. A ceiling that sags or bulges with water needs attention straight away.
A felt patch typically lasts 3 to 7 years and an EPDM seam repair 10 to 15 years, while a temporary seal lasts weeks or months. The age of the whole roof matters as much as the repair, and the flat roof replacement cost guide sets out how long felt, EPDM and GRP roofs last.
A fair flat roof repair quote names the cause of the leak, the repair method and material, the access needed, whether the deck will be checked, the guarantee and whether VAT is included. A per square metre rate for a single leak, or pressure to replace a whole roof because of one fault, is a good reason to get a second quote.
A flat roof repair is only as good as the diagnosis behind it, and the cheapest patch is poor value if it goes over a wet deck or a ponding area. Bernard Andrews Roofing repairs felt, EPDM and GRP flat roofs across London, from garage roofs and kitchen extensions to balconies and dormers. Get in touch for a quote, or book a roof survey if the roof has leaked more than once.
Most flat roof repairs cost £150 to £500 in 2026. London prices for felt, EPDM...