Flat RoofingContractors
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Repairs and surveys

Flat roof repairs that fix the real cause of a leak

A flat roof repair fixes a specific defect, such as a split, a lifted seam, a failed upstand or a blocked outlet, without replacing the whole covering. It makes sense when the rest of the roof is sound and dry, and we will tell you plainly if it isn't.

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Roofer cutting out a blister on an old mineral felt flat roof before a patch repairComputer-generated example image
Guide price
£150–£500
Repair price
Confirmed once the leak or damage is found
Condition survey report
£150–£300
Coverage
England, Wales, Scotland, NI

How much does a flat roof repair cost?

A localised patch repair costs £150–£500 as a guide, with upstand, flashing and outlet work priced separately. The final figure depends on the system, how easy the roof is to reach and how much of the surrounding covering has to be cut back to sound material.

RepairGuide price
Localised patch repair£150–£500
Upstand, flashing or abutment repair£250–£650
Outlet or drainage repair£120–£350
New edge and drip trims£12–£22 per metre

These are guide prices including VAT at 20%. We confirm a fixed price in writing after inspecting the roof, before any work starts. Scaffold for a two-storey roof or a dormer adds £450–£950. If the inspection shows the roof needs replacing, the survey and written quote for that are free and carry no obligation. The cost guide lists full replacement prices for comparison.

Should I repair or replace my flat roof?

Repair it if the defect is isolated and the rest of the roof is sound, dry and still well within its working life. Replace it if leaks keep coming back, cracking or blistering is widespread, the insulation is wet or the deck feels soft underfoot.

A useful test is to ask whether a repair would still look sensible if a second leak appeared somewhere else a few months later. On a roof near the end of its life, patching one split tends to move the problem rather than solve it, and repeated call-outs soon add up to a large share of the cost of a new roof. On a roof that is a few years old with one storm-damaged lap, a repair is the right answer and we will say so.

Our repair or replace guide sets out the signs in more detail, and the lifespan guide gives typical service lives for each system.

Why does a flat roof leak in one place but drip somewhere else?

Because water rarely comes through the ceiling directly below the hole. It gets in at one point, runs along the deck, a joist or the top of the insulation, and drips wherever it finds a low spot or a gap in the ceiling.

That is why a patch over the damp patch so often fails. Before we repair anything, we work back from the stain to the likely entry point and check the usual weak spots: upstands where the roof meets a wall, flashings and cavity trays above them, laps and seams, outlets and gutters, drip trims, rooflight kerbs, and any fixings or cables that pass through the covering. The fault is frequently at an edge or a wall rather than in the middle of the roof.

Sometimes the cause isn't the roof at all. Defective pointing, a failed cavity tray or a cracked coping above the roof can let water in behind the upstand, and condensation in a cold roof can look exactly like a leak. Our guide to flat roof leaks covers these causes. If the path can't be found by inspection, a leak tracing survey is the next step.

Which repair materials work with my type of flat roof?

The repair has to use the same system as the roof, because many flat roof materials don't bond to each other and some damage each other.

  • Torch-on felt: repaired with compatible bitumen membrane, cut back to sound felt and lapped well beyond the defect. Torching near timber, insulation or fascias needs care, and some details are better done with cold-applied methods.
  • EPDM rubber: repaired with EPDM patches and the manufacturer's primer and seam tape. Bitumen products and many general-purpose sealants won't bond to EPDM and shouldn't be used on it.
  • GRP fibreglass: the area is ground back, then new resin and glass matting are laid and finished with topcoat to match.
  • Liquid-applied and single-ply: repaired with the same manufacturer's products wherever possible, as mixing systems can affect a material guarantee.
  • Mastic asphalt: cracks and blisters are cut out and made good with new asphalt by an operative who works with it.

A tin of roof sealant or bitumen paint may stop a drip for a while, but on the wrong membrane it makes a proper repair harder later.

What do you check and do on a repair visit?

We inspect the whole roof, not only the spot that is leaking, and tell you what we have found before any work starts.

A typical visit covers the covering itself (splits, blisters, crazing, lost chippings and open laps), the upstands and flashings at walls, edge trims and drips, outlets and gutters, any rooflights, and how water sits on the roof after rain. Where it is safe to do so, we check the deck for soft spots. Every roof is treated as fragile until a competent person has confirmed otherwise, and edge protection goes in before anyone works near an open edge.

The repair itself means cutting back to sound material, drying the area and repairing with the same system. We clear the outlets while we are up there, because a blocked outlet is a common reason a repaired roof leaks again. What the repair covers, and what it doesn't, is set out in the written quote.

How long will a flat roof repair last?

A well-made repair on a roof that is otherwise sound should last as long as the covering around it. It can't add years to the rest of the roof, though.

If your felt roof is twenty years old, a perfect patch still leaves twenty-year-old felt around it, and the next weak point will appear in its own time. That is why we give you an honest view of how much life the roof has left, so you can decide whether a repair now and a planned replacement later is better value than replacing straight away.

Simple care helps any repair last. Clearing leaves from outlets and gutters, keeping people off roofs that aren't designed for foot traffic, and looking over upstands and edges after storms all catch small problems before they reach the ceiling. Our maintenance guide lists the checks worth doing each year.

What's included when we do the work?

  • Inspection of the whole roof, not just the wet patch
  • Leak path traced from the stain back to the entry point
  • Repairs with materials compatible with your roof system
  • Upstands, flashings, laps and seams made good
  • Outlets and gutters cleared while we're on the roof
  • Fixed price confirmed in writing before work starts

What do guide prices look like?

Guide prices including VAT at West Midlands rates; regional pages adjust these for your area. We confirm the price once we've traced the leak or seen the damage.

JobGuide price inc VAT
Localised patch repair£150–£500
Upstand or flashing repair£250–£650
Outlet or drainage repair£120–£350
Emergency temporary weatherproofing visit£180–£450
Condition survey and leak investigation£150–£300

Does anything differ outside England?

  • Wales: Most re-roofing in Wales needs building regulations approval, so check whether it applies if more than 25% of the roof is being repaired or replaced. A small patch repair normally falls well below that.
  • Scotland: Like-for-like repairs to a roof covering can be exempt from a building warrant in Scotland, but check with the council's building standards team before anything larger. Wetter western areas see more wind-driven rain, so upstands and flashings deserve a close look.
  • Northern Ireland: A small patch repair in Northern Ireland is unlikely to need approval, but contact the district council's building control before anything that replaces a large part of the roof. Safety on domestic work falls under CDM (NI) 2016.

How does the job run from start to finish?

  1. Tell us about the leak

    Let us know where the damp shows, when it appears and what the roof is made of, if you know. A rough idea of the roof's size and height helps us plan access.

  2. Inspect and trace

    We inspect the roof, trace the leak path and explain what we've found, including whether a repair is the sensible option.

  3. Fixed written price

    You get a fixed written price for the repair. If replacement is the better answer, the survey and quote for that are free.

  4. Repair and tidy up

    We cut back to sound material, repair with compatible products and clear the outlets, then show you what was done before we leave.

Questions about flat roof repairs

How long does a flat roof repair take?

Most small repairs take a few hours on site once the roof is dry. Larger upstand or outlet repairs can take a day or more, and setting up scaffold or access equipment adds time.

Who carries out the repair?

Vetted roofing teams working under S&K Property Investments and Improvement Ltd, part of the S&K Group, which is the company you contract with. The price and scope are agreed in writing before work starts.

Can a GRP roof be repaired?

Yes. The damaged area is ground back, new resin and matting are laid over it and a matching topcoat goes on top. Cracks that keep reappearing along the same line often point to movement in the deck, which needs fixing first.

Will a repair affect my roof's guarantee?

It can. If the roof is still under a manufacturer's material guarantee, the repair should normally use that manufacturer's products and methods, so share any guarantee paperwork with us before work starts.

Do I need building regulations approval for a flat roof repair?

Not usually for a patch repair. Replacing a large part of the covering over a heated room is treated differently and can bring in the thermal upgrade rules.

Why does my flat roof only leak in heavy rain?

Usually because water only reaches a weak point when it builds up: a partly blocked outlet, a low spot where water ponds, or an upstand that is too low for the depth of water. Wind-driven rain against a wall above the roof is another common cause.

Can you repair the roof if the ceiling is already damaged?

Yes. The roof is fixed first so the ceiling can dry out, and then a plasterer or decorator can make it good. Any wet insulation within the roof should be checked, as it may need replacing.

Related services

Emergency leak repairs

Temporary weatherproofing for a leaking flat roof, followed by a proper permanent repair.

Flat roof surveys and leak tracing

Condition surveys and leak tracing with moisture readings, core checks and a written report.

Edge trims, outlets and drainage

Drip trims, kerbs, outlets, gutters, overflows and ponding fixes for flat roofs.

Flat roof replacement

Full strip and re-roof of tired flat roofs, with new deck, insulation and falls where needed

Where do you offer flat roof repairs?

Get a fixed price for your flat roof

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