Liquid waterproofing
Cold-Applied Liquid Waterproofing & Detailing
Cold-applied liquid waterproofing is a liquid-applied membrane that cures into a continuous, joint-free waterproof layer. Applied without heat or flame, it waterproofs the shapes sheet membranes struggle with: upstands, penetrations and complex details. The system we install is HYDRONYLON, and we name it here for the same reason we name it in a specification: you should know what is going on your roof.
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Where liquid earns its place
Most flat roof leaks start at details, because details are where sheet membranes have to be cut, folded and lapped. A liquid system has no laps: it is applied wet, reinforced at stress points, and cures as one continuous layer around whatever shape it meets. We specify it where that property matters most:
- Upstands, kerbs and edge details
- Pipe and cable penetrations, vents and plant bases
- Complex junctions where several planes meet
- Safe2Torch zones: anywhere an open flame is ruled out
- Full-roof overlays on suitable, dry, well-prepared substrates
Full-roof overlays, not only detailing
The last item on that list is the one people underestimate. Where a survey finds an existing covering that is dry underneath, soundly bonded and worth keeping, the whole field of the roof can be overlaid in liquid rather than stripped back to the deck. That turns liquid from a detailing material into a full refurbishment route: no tear-off skip, no exposed deck, and the finished roof is one continuous membrane from parapet to outlet. Whether your roof qualifies is a survey question, never a sales one, and it is set out in the refurbishment options guide.
The Safe2Torch partner to torch-on felt
On most of our roofs, liquid waterproofing works alongside reinforced bituminous membrane (RBM) rather than instead of it. The field of the roof gets the robustness of a torch-applied built-up system; the details near timber cladding, eaves boxes and other combustible construction get a cold-applied finish that needs no flame at all, in line with the industry Safe2Torch guidance. Each material does the job it is best at.
Named in the specification, with published credentials behind it
Plenty of roofing quotes say "liquid system" and stop there, which leaves you unable to check anything. Ours says HYDRONYLON, along with the build-up, the reinforcement and the preparation, before a tin is opened. A named system is a system you can look up, and the credentials it publishes are these:
- Assessed under European Technical Assessment ETA-23/0735, the European route by which a waterproofing system is independently examined against a defined standard.
- A confirmed durability of 10 years stated in that published assessment.
- A 10-year product guarantee route existing within the system, on the manufacturer's own published terms.
Those are the system's credentials as its manufacturer publishes them, not ours: HYDRONYLON is a separate company with its own documents, and you can read them on the system's own site. What we bring is the survey that decides whether it suits your roof, the specification that pins down how it goes on, and the workmanship that makes any published figure mean something. Whatever guarantee applies to a given roof is confirmed in writing with the quote, never implied on a web page.
Part of a bigger decision?
If the whole roof is tired rather than just its details, start with the options guide on our flat roof refurbishment page, or commission a condition survey and let the evidence choose the system.
Book a surveyFrequently asked questions
What is cold-applied liquid waterproofing?
A waterproofing system applied as a liquid, usually with reinforcement at stress points, that cures into a continuous, joint-free waterproof membrane. Cold-applied means no torch and no open flame: the material bonds and cures without heat.
Where is liquid waterproofing better than torch-on felt?
Anywhere geometry or fire risk makes sheet membrane awkward: upstands, pipe penetrations, rooflight kerbs, plant bases, complex junctions and any Safe2Torch zone near combustible details. Because it is applied as a liquid, it follows shapes a sheet cannot, without laps or joints at the most leak-prone points.
What is HYDRONYLON?
HYDRONYLON is the liquid-applied waterproofing system Pluvian installs: a cold-applied membrane system assessed under European Technical Assessment ETA-23/0735, with a confirmed durability of 10 years stated in its published assessment and a 10-year product guarantee route within the system. It is its own manufacturer with its own site; naming it here tells you exactly what goes on your roof.
Can liquid waterproofing go over an existing roof?
On suitable substrates, yes, and this is a refurbishment route in its own right, not just a detailing trick. The existing covering must be dry underneath, sound and properly prepared, and adhesion is checked before the system is specified. Where those conditions hold, a liquid overlay renews the whole roof without a strip.
Is it safe near timber and combustible details?
Yes, and that is one of its main jobs. Because the system cures without heat, it is the industry-recognised way to waterproof details where the Safe2Torch guidance rules out an open flame: timber cladding, eaves boxes and junctions with lightweight construction.
How long does liquid waterproofing last?
For the system we install, the published answer is concrete: the HYDRONYLON assessment under ETA-23/0735 states a confirmed durability of 10 years, and a 10-year product guarantee route exists within the system. Beyond any published figure, preparation, detailing and maintenance decide how a real roof performs.
Got a detail that keeps leaking?
Upstands, kerbs and penetrations are exactly where liquid systems shine. Send us a photo and we will tell you what we would do.
Report a leak