Torch-On vs Self Adhesive Felt

Insulation, Membranes & Felts
torch on felt being felt

Across the years, experts have always been looking for better and better ways to keep on our homes safe, warm and protected from the rain. For the last 100 hundred years a key component of that formula for flat roofs has been roof felt.

Naturally, it is difficult to compare to hardier roof coverings like tiles and slates but remains the original and go-to option for garages, large commercial buildings and flat-roofed extensions. But what is the best type of felt? Of course, it couldn’t be as simple as there only being one choice to make, but below we’ll help break through the jargon and make the decision a simple one.

Why Use Roof Felt on Flat Roofs?

Unlike our homes, which are protected by tiles, slates and other hardier roof coverings, you are far more limited with flat roofs. Typically having the choice between felt or rubber. Both can serve as exceptional moisture barriers, providing decades of protection from rain, sleet and snow but felt tends to be the DIYers' choice.

Why? Well, it is far more cost-effective for a start, as well as far quicker and easier to repair yourself in the event of a blister, tear or crack. It’s also incredibly low maintenance and leaves a nice seamless finish – as long as it is installed correctly. All in all, felt is forgiving. The perfect choice for garages, dormer conversions, extensions and porches.

What is Torch-On Felt?

It is simpler to think of torch-on felt as the ‘heavy duty’ option. It would have to be considering, as you might have already guessed, that you need a blow torch for its application. This felt is more often than not comprised of three layers – enough to create a near impenetrable barrier. It’s also for his reason that torch-on felt is seen as the go-to (with the expectation of rubber roofing) for larger commercial buildings and those that see more regular foot traffic.

The first and most important thing to remember here, however, is that this is absolutely NOT a DIY-friendly option. We would never recommend working with an open flame, as you would have to if you have no prior experience. That being the case, torch-on felt will need to be installed by a professional which will naturally increase the price of its application.

All that said and when all is done, torch-on felt is still considered one of the quickest and most reliable solutions to weather-proofing your flat roof. It is not only a phenomenal barrier against rain but also UV rays and strong winds. In essence, it can quite adequality handle almost everything our turbulent British weather can throw at it. Helping to keep temperatures inside the building regulated all year round.

What is Self-Adhesive Felt?

Self-adhesive felt lands on almost the complete opposite end of the scale. Requiring no open flame for installation. This means that it is perfectly safe (and often preferred) for DIY applications on garages, sheds, porches and other smaller, but habitable, areas of your home. As opposed to the bituminous layer that needs to be bonded to the roof deck with fire, self-adhesive roofing felt simply peels off at the bottom (much like double-sided tape) where it can quickly and safely adhere.

As an added bonus, self-adhesive felt is the more cost-effective option per meter squared. Making it a particularly stress-free material, one that you can afford to over-buy to make sure you have enough to cover all areas of your roof with enough spare to allow for future repairs. Being tailored towards homeowners no tools and only basic skills are needed for a finish that is capable of keeping the weather at bay for years – up to 15 depending on the brand.

Benefits & Drawbacks

Torch-On Felt

The table below lists the core benefits and drawbacks of torch-on felt, suitable for use on most concrete, timber and metal deck flat roofs. Though often seen in use on larger commercial buildings, it can serve equally well on residential applications – particularly garage conversions.

Under no circumstances should this felt be installed directly to a timber roof deck or upstands. Even if treated, as you might expect this would prove to be a fire hazard.



Quick & Easy for professionals to install

Professional help required for installation

Can be applied in both dry & wet conditions

Additional labour will increase installation costs

Resistant to UV Rays, rain & wind


Self-Adhesive Felt

Self-adhesive felt, as mentioned above, is the ideal choice for smaller projects at home. This can include anything from garages, dormers, sheds, porches and more covering most residential buildings with flat roofs. Whilst it is a popular DIY choice, it’s also a popular choice with most professional roofers who would be able to install it far more quickly than torch-on.



Easy & safe DIY Installation

Unsuitable for larger commercial buildings

Cost-effective, ideal for home improvement projects


Years of moisture protection


 How Much Does Felt Installation Cost?

Felt installation tends to be on the cheaper end of the spectrum, when compared with GRP and fibreglass solutions, though can range dramatically depending on the surface area being covered and the initial condition of the roof deck. Naturally, if any repairs need to be made beforehand this can impact the cost significantly.

Average Costs of Re-Felting a Flat Roof


3-Layer Felt (Torch-on, Single Garage


Replacement Cost

£40 – 60 /m²

£9 – 10 /m²


Bear in mind these costs could come in addition to labour, disposal and any repair work or additional equipment your chosen roofer may need. Scaffolding hire alone can cost as much as £1100 per week or more.

With all that in mind, it is clear to see that self-adhesive is by far friendly to your wallet. The only drawback is the time you’d have to invest yourself to make the most of these savings with a DIY fitting.

Final Thoughts

At first glance, it may seem a difficult choice between torch-on and self-adhesive felt but the two could not be more different. It all comes down to the size and scale of your project. For commercial buildings, larger garages and other sizeable habitable areas, the reliability of torch-on felt is all but essential.

On the other hand, for DIYers looking to test their skills on small garages, extensions and porches self-adhesive is the clear winner. Cheaper, safer and requiring very little experience to install.

For more information on our range of roof felt, or if you have any questions tailored to your specific project (whether that be about felt or any other area of roofing), please get in touch with our award-winning customer service team. Simply call us on 01295 565565 or use the handy live chat below. We’ll be happy to help.

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