Flat Roof Leak Detection in London
A flat roof that keeps leaking after repeated patch repairs is one of the most frustrating property problems you can face. The water often appears inside at a point several metres from the actual breach, because it travels beneath the membrane, along insulation layers, and through structural details before finding a way in. Without detection equipment, every repair is a guess.
Signs Your Flat Roof Has a Leak
A flat roof that keeps leaking after repeated patch repairs is one of the most frustrating property problems you can face. The water often appears inside at a point several metres from the actual breach, because it travels beneath the membrane, along insulation layers, and through structural details before finding a way in. Without detection equipment, every repair is a guess.
ClearFlow uses electronic leak detection and thermal imaging to locate the precise point of failure on any flat roof membrane. Our engineers survey the roof surface using low-voltage electrical current testing, which identifies the exact position of any breach in an EPDM, GRP, felt or single-ply membrane without lifting or cutting it. You receive a written survey report at the end of the investigation, with photographs of the identified breach location and a clear repair recommendation.
In London, flat roofs are common on Victorian rear extensions, residential extensions, and purpose-built apartment blocks. They are also found on commercial and mixed-use properties throughout the city. Whatever the construction, the investigation method is the same: non-destructive, accurate, and backed by a written report that your roofer, managing agent or insurer can act on directly.
- Damp patch on ceiling below the flat roof
- Water staining on internal walls near the roof edge
- Visible pooling or standing water on the roof surface
- Blistering or bubbling of the roofing membrane
- Felt or membrane pulling away from the parapet wall
- Persistent damp smell in the room directly below
- Multiple patch repairs that have failed to stop the leak
- Wet insulation or timber discovered during a roof inspection
How We Locate Flat Roof Leaks in London
We review the symptoms, building type and pipe layout before selecting any equipment.
One or more methods are deployed to identify the source zone, typically narrowed to within 10–30 cm.
A second method cross-checks the result before we mark the repair point — no guesswork.
A written report with findings and photographs is issued — suitable for insurance claims.
Flat Roof Situations We Investigate
Rear extension flat roof
The most common scenario we investigate in London. Water penetrating a rear extension roof often enters through a failed upstand junction, a cracked GRP seam, or where the membrane meets a vertical surface. We identify the breach without disturbing the roof covering, so repairs can be targeted precisely.
Leasehold flat with a roof above
If you own a leasehold flat and the roof is the freeholder's responsibility, a documented investigation report is often required before the landlord will authorise repairs. Our written report records the source, the method used and the repair recommendation, in a format accepted by managing agents and insurers.
Commercial or retail flat roof
Business owners often discover roof leaks only when water reaches internal fittings or electrical equipment. We survey large commercial flat roofs using electronic testing and mark breach locations on a scaled plan, so your contractor can prioritise repairs with minimal disruption to the building's operation.
Trace and access insurance claim
Trace and access cover applies to flat roofs where the source of ingress must be confirmed before repairs can be authorised. We produce the written evidence your insurer requires, including photographs and method statements, and can liaise directly with your loss adjuster on request.
Flat roof leaking after repair
A roof that leaks shortly after a professional repair raises questions about workmanship. Our independent survey provides documented evidence of whether the original breach has been sealed correctly, or whether a new failure has developed elsewhere, which protects your position in any contractor dispute.
Green or sedum flat roof
Detecting leaks beneath a sedum or green roof presents additional challenges because the growing medium conceals the membrane. We use electronic testing methods that work through the substrate to locate the exact breach without disturbing the planting or requiring the growing medium to be removed.
What You Can Expect
We've been detecting hidden leaks across London for years. Every engineer is directly employed by us, DBS-checked and WaterSafe registered. We don't subcontract.
- Pinpoints the exact membrane breach without lifting or cutting the roof
- Includes a written survey report, accepted by insurers and managing agents
- Electronic testing works across EPDM, GRP, felt and single-ply membranes
- No Find No Fee: if we cannot locate the breach, you pay nothing
- Covers flat roofs on domestic, leasehold, commercial and mixed-use properties
- Responds across all 32 London boroughs, on-site within 2-4 hours for urgent cases
Trusted Across London
Absolutely quality service and what plumbers should exemplify. Turned up when they said, was kind, answered all my questions and wasn't being dodgy with anything. Skilful and efficient! Would highly recommend.
The technician arrived on time, was polite, and explained the process clearly before starting. They used advanced, non-invasive equipment to locate the leak quickly without causing any unnecessary damage to my property.
Really impressed with the service. They responded quickly and were able to accurately detect the leak without causing unnecessary damage. Professional, efficient, and clearly experienced — would highly recommend to anyone dealing with a hidden leak.
Wayne and his colleague came and within an hour found the leak deep underneath my cellar and came up with a perfect plan which made the pipe redundant and re-routed it the following morning. An excellent option if you're having a problem with a leak you cannot find.
Called Wayne Monday and he was round Tuesday evening — came out of hours to help me out. Very professional, punctual and great with communication. Fair priced too. Will definitely recommend and use again.
Contacted them and they were at the property within an hour. Honest, well priced and gave a detailed report that will likely save me hundreds of pounds. Will definitely recommend and if necessary will use again.
Wonderful efficient service — came out the same day, nothing was too much trouble. Engineers were professional and polite, explained the problem and persevered until the blockage was cleared. Would highly recommend this company.
The staff were so professional and friendly. The technician was nice and informative — he advised me the leak was outside and wrote me a report which I sent to Thames Water. In a few days they sent a repair team and found the leak. Clear Flow are great at what they do.
I received a letter from Thames Water about high water usage. Wayne arrived on time, was so professional, guided me through what he was doing and advised me of the next steps. He also wrote me a report to send to the water board. 100% recommend.
How Electronic Leak Detection Works
Electronic flat roof leak detection works by using the electrical conductivity of water to pinpoint membrane failures. The engineer connects a low-voltage return circuit to the roof structure and passes a handheld detector across the membrane surface. At any point where water has permeated through a breach, the circuit is completed and the detector registers a signal. The position is marked, photographed and logged. The process typically takes between one and three hours depending on roof size, and leaves the membrane undamaged throughout.
On-Site Survey Process
When our engineer arrives, the first step is a visual inspection of the roof surface, upstands, flashings, drains and parapets. This helps identify areas most likely to have failed and informs where the electronic survey is focused. We also check whether the membrane is wet, because electronic testing works best when the surface has been allowed to dry. If conditions require it, we can survey wet membranes using specialist conductivity probes at closer pass intervals.
Written Survey Report
At the end of the investigation, you receive a written survey report. This includes the method used, photographs of the breach location, a clear description of the failure type and a repair recommendation. The report is formatted to be used directly by your roofing contractor, managing agent or insurance company. If you are making a trace and access claim, we can confirm the report format your insurer requires before we attend.
Why Flat Roofs Fail in London
Flat roofs in London fail for a range of reasons. Thermal movement causes membrane seams to pull apart over years of seasonal expansion and contraction. Foot traffic from maintenance visits creates small tears that worsen under standing water. Flashings lift at parapet junctions as the wall and roof structure move independently. All of these failures are difficult to locate visually because the water that appears inside can travel considerable distances beneath the membrane before it enters the building.
Flat Roof Leak Investigations
FAQs About Flat Roof Leak
Can't find what you're looking for? Call us on 0203 886 2316 and we'll answer on the spot.
How does flat roof leak detection work?
We use low-voltage electronic testing on the roof surface. A small electrical current is connected to the roof structure and a handheld detector is passed across the membrane to identify points where moisture is causing conductivity through a breach. The position is marked, photographed and recorded in a written report. No part of the roof is damaged in the process.
How much does flat roof leak detection cost?
The cost depends on the size and complexity of the roof. Most residential flat roofs in London are surveyed for a fixed fee, which includes the written report and photographs. We confirm the price before attending. If we cannot locate the source of the leak, our No Find No Fee guarantee means you pay nothing for the investigation.
Can you detect a leak on a flat roof without lifting the membrane?
Yes. Electronic leak detection identifies the breach from the surface without lifting, cutting or stripping the roofing material. The roof remains intact throughout the investigation. Access work only begins once the exact location has been confirmed and a contractor is ready to carry out the repair.
Is flat roof leak detection covered by home insurance trace and access?
Many home insurance policies include trace and access cover, which pays for the cost of locating a leak, including on a flat roof. Your insurer will require a written investigation report documenting the source and the method used to find it. Our reports are accepted by all major UK insurers and can be provided directly to your loss adjuster.
How do I find a flat roof leak detection specialist near me?
ClearFlow covers all of London and the surrounding counties. If you have a flat roof leak anywhere in London, contact us by phone or online and we will confirm availability and a fixed price before attending. We aim to be on-site within 2-4 hours for urgent cases across all 32 London boroughs.