Torch-on Felt Roof Alternative
Torch-on felt roofs require the use of naked flames during installation and rely on multiple lapped joints. We overlay your existing roof with Ultraflex—a cold-applied waterproofing system that bonds directly to felt, eliminates hot works on site, and provides a seamless waterproof membrane backed by a 20-year guarantee.
The problems with torch-on felt roofs
The quality of torch-on felt roofs varies significantly. During our leak investigations, we regularly encounter low-quality systems that have been poorly installed. Multiple layers of bitumen are flame-bonded on site, resulting in numerous joints, a limited lifespan, and an increased fire risk during installation.
Cracks, blisters and bubbles
Bitumen hardens and shrinks with age and UV, causing surface cracking, blistering and trapped-air bubbles that rupture and leak.
Open flame fire risk on install
Torch-applied felt uses a naked gas flame against the deck and any nearby timbers - one of the leading causes of building fires during roofing works.
Multi-layer system with weak laps
Three layers of underlay, intermediate and cap sheet, all bonded at overlapping laps. Every lap is a potential failure point as the bitumen ages.
Short lifespan
Even well-installed felt typically lasts 10-15 years before noticeable failure - far less than modern liquid systems.
Weather-driven degradation
Sun, frost, ponding water and thermal movement all attack the bitumen, leading to brittleness, splits and loss of waterproofing.
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Why we install our waterproofing system over felt
Felt is a short-life material that cracks, bubbles and shrinks within years, and torch-on installation introduces a real fire risk to your property. Our waterproofing system is cold-applied with no flame, bonds directly over your existing felt, and delivers a seamless 20-year waterproof layer for a fraction of the cost of a full strip-out.
One of the best flat roof waterproofing systems on the market
Whatever flat roof job you have - installation, repair, replacement, Asphalt, GRP, EPDM or torch-on felt overlay - we install the Ultraflex cold-liquid waterproofing system. It's the most durable, cost-effective, and reliable flat-roof solution available.
By overlaying your existing roof with Ultraflex, we save you the cost and disruption of a full strip-out while delivering a fully bonded, seamless waterproof layer backed by a 20-year guarantee. We go in, repair your existing roof and seal it for decades of protection - if needed, we can apply bespoke finishes and solutions post-waterproofing.
Why we install Ultraflex on every job
Faster installation
Fast-curing and rainproof in as little as 30 minutes.
Up to 50% cost savings
Overlay your existing roof and avoid strip-out costs.
20-year guarantee
Proven waterproofing built for long-lasting protection.
100% Compatible
Torch-on felt, asphalt, GRP, timber, concrete, and virtually any roof surface.
Safer installation
Cold-liquid application, eliminating fire risk.
Seamless waterproofing
No joints or laps - a fully bonded waterproof layer.
How we work:
Instant Estimate
Fill out our cost estimate tool to receive a fast, ballpark price based on your project details. It's a quick way to understand likely costs before moving forward.
Site Visit + Detailed Quote
We carry out a site visit where needed to assess your roof in detail, then provide a clear, itemised quote with no hidden costs so you know exactly what to expect.
Installation
Our trained team prepares the surface and installs the Ultraflex system, delivering a seamless, fully bonded waterproof finish built to last.
Sign-off & 20 Year Guarantee
We inspect the roof, hand over your 20-year guarantee documentation, and leave the property spotless.
How Ultraflex compares
See how our Ultraflex cold-liquid waterproofing system stacks up against traditional flat roof systems across the things that matter most.
| Criteria | Ultraflex | GRP | EPDM | Asphalt | Torch-on Felt |
|---|---|---|---|---|---|
| Seamless, fully bonded | |||||
| Cold-applied (no flame) | |||||
| Rainproof in 30 minutes | |||||
| Overlay existing roof | |||||
| 20-year guarantee | |||||
| Cost-effective long-term | |||||
| Resists cracking & shrinking | |||||
| Suitable for complex detailing |
Ultraflex over existing felt is typically up to 50% cheaper than a strip-and-replace job, and lasts far longer. Use our estimator for a quick price.
Why Ultraflex — FAQs
The most common questions we get asked about the Ultraflex cold-liquid waterproofing system.
How long does a torch-on felt roof actually last?
A good three-layer felt roof, properly installed with well-formed laps, will usually give ten to fifteen years, and sometimes twenty on a sheltered roof with good falls. Poorly torched laps, standing water or a south-facing aspect can cut that to well under ten. The mineral cap sheet losing its granules and the laps beginning to lift are the clearest signs the roof is near the end of its service life.
Can you install over my existing felt roof rather than stripping it?
Yes, in the great majority of cases. Bitumen felt is a substrate the Ultraflex system bonds to well once it has been cleaned, made good and primed. We only recommend stripping where water has already saturated the insulation or damaged the deck, because sealing over wet build-up traps the moisture rather than solving the problem.
Do you use a gas torch anywhere on the job?
No. The entire system is cold applied by roller and brush. There is no naked flame, no gas bottle on the roof, and no requirement for a hot works permit or a fire watch afterwards, which is one of the main reasons managing agents and schools prefer it on occupied buildings.
Why do felt roofs always seem to leak at the joints?
Because the joints are the only part of the roof made by hand on site. The felt sheet itself is a factory-made product of consistent quality, but every lap is welded manually with a torch, and both under-heating and over-heating produce a bond that will fail before the sheet does. As the bitumen hardens with age, thermal movement concentrates stress on exactly those lap lines.
Is a liquid overlay more expensive than a new felt roof?
Not usually, once the full picture is compared. A like-for-like felt replacement includes stripping and disposing of the old covering, which the overlay avoids entirely. The liquid system also lasts considerably longer and carries a twenty-year guarantee, so the cost per year of service life is markedly lower even where the up-front figures are similar.
What happens to the ponding water on my felt roof?
The membrane itself is unaffected by standing water, unlike bitumen felt, which degrades where water sits. Where ponding is severe we can also build up falls locally before waterproofing so the water reaches the outlets, and we will always tell you at survey stage whether that work is worth doing on your roof.
Services tailored to your flat roof, we work on any job.
From new installations and full system refurbishments to targeted leak diagnostics and repairs, every project is carried out by our in-house specialists using premium, manufacturer-approved liquid waterproofing systems.
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