Flat Roof Leak Repair in London
A leaking flat roof rarely fixes itself, and patch after patch is rarely the real answer. HYDRONYLON® is a liquid-applied waterproofing system that bonds over your existing flat roof to form one continuous, watertight layer, with no welded seams or laps to fail. It is fitted across London by independent HYDRONYLON Approved Contractors and backed by a 10-year guarantee.
Repair, or overlay the whole roof?
Most flat roof leaks come from a covering that is reaching the end of its life: splits in ageing felt, failed laps and flashings, or ponding water sitting on low spots. Stripping the whole roof back to the deck and starting again is one option, but it is the most disruptive and the most costly. In many cases a flat roof in sound structural condition can instead be cleaned, prepared and overlaid with a liquid-applied membrane, solving the entire roof in a single pass rather than chasing one leak after another. A HYDRONYLON Approved Contractor will inspect your roof and tell you honestly whether a localised repair or a full overlay is the right call.
Why a liquid-applied system solves a leaking flat roof
Felt and single-ply roofs tend to leak at their weakest points: the laps, the welds and the upstands. HYDRONYLON is designed to remove those weak points.
- Seamless, with nothing to come apart. The system cures into one continuous membrane with no field seams, so the joints that normally fail are designed out from the start.
- Fitted over your existing roof. Once the surface is prepared, HYDRONYLON is applied directly over the existing covering. There is usually no need to strip the roof back to the deck, which keeps disruption, waste and cost down.
- Cold-applied, with no naked flame. The system is applied cold by brush, roller or spray. There are no torches, no hot works and no open flame on your roof, which matters on occupied buildings and wherever hot-works permits are difficult.
- Fully bonded and watertight. The membrane bonds fully to the prepared substrate and is independently assessed as watertight, so wind cannot lift it and water cannot track beneath it.
- Built for flat and low-pitched roofs. The system is designed for flat and low-pitched roofs and performs across the British climate.
Suitable for most flat roof types
HYDRONYLON is designed to overlay the flat roof coverings found across London homes and commercial buildings:
- Bituminous felt and torch-on roofs (see felt roofs)
- Metal roofs and gutters (see metal roofs)
- Concrete and other mineral substrates (see mineral substrates)
- Single-ply PVC membranes (see PVC membranes)
Fitted by Approved Contractors, backed by a 10-year guarantee
HYDRONYLON LTD is a British company supplying a European-certified waterproofing system, assessed under European Technical Assessment ETA-23/0735. We do not fit roofs ourselves. The work is carried out by independent HYDRONYLON Approved Contractors, trained and certified on the system and working across London. A flat roof installed by a HYDRONYLON Approved Contractor comes with a 10-year guarantee.
Flat roof projects in London
Real flat roof projects completed in London using the HYDRONYLON system.
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Leaking felt roof sealed in Shepherd's Bush, London W12 Felt · 65 m² · 6 August 2025 A worn felt flat roof in Shepherd's Bush, London W12 was leaking into the flat below. See how the HYDRONYLON liquid-applied system sealed all 65 m² in four working days, with no strip-off. Read case study → -
Leaking lead and parapet roof sealed in Whitechapel, London E1 Lead & parapet · 78 m² · 18 August 2024 A pitched parapet roof on Whitechapel Road in London E1 was leaking through cracked, worn lead into the flats below. See how the HYDRONYLON liquid-applied system sealed the lead, parapet copings, valleys and details, with no lead replacement or tear-off. Read case study →
Frequently asked questions
Does HYDRONYLON repair my flat roof directly?
No. HYDRONYLON LTD is the UK importer and distributor of the system. The work is carried out by independent HYDRONYLON Approved Contractors, who are trained and certified on the system and work across London.
Can a leaking flat roof be repaired, or does it have to be replaced?
A flat roof that is in sound structural condition can often be cleaned, prepared and overlaid with a liquid-applied membrane rather than stripped and replaced. An Approved Contractor will assess your roof and advise whether a localised repair or a full overlay is the better option.
Is liquid-applied waterproofing suitable for my type of flat roof?
HYDRONYLON is designed to overlay bituminous felt and torch-on roofs, metal roofs and gutters, concrete and other mineral substrates, and single-ply PVC membranes. You can see each roof type on our applications page.
How disruptive is the work?
The system is applied cold by brush, roller or spray, with no torches, no hot works and no naked flame. It is fitted over your prepared existing roof, so there is usually no full strip-off, which keeps mess and disruption to a minimum.
Is the work guaranteed?
A flat roof installed by a HYDRONYLON Approved Contractor comes with a 10-year guarantee.