Felt roof installation is a time-tested method of creating strong, weather-resistant roofs for a wide variety of buildings, from small garden sheds to large-scale flat roof extensions. Whether you’re a seasoned roofing contractor, a property developer, or a homeowner taking on a DIY project, understanding how felt roofing works, what materials are best, and how to ensure a long-lasting finish is essential for getting the job done right.
Felt roofing has been used for decades in the UK due to its affordability, simplicity, and proven performance in the face of unpredictable weather. Modern felt systems have come a long way from the brittle, short-lived materials of the past. Today’s high-performance felts are designed with durability in mind, featuring reinforced layers, UV protection, and more flexible, weather-adaptive surfaces that last longer and offer better all-around protection.
A felt roof typically consists of two or three layers, including an underlay and a top felt known as a cap sheet. These layers work together to seal the roof from water ingress, resist wind uplift, and provide a tough outer surface that can withstand rain, hail, snow, and years of wear. Flat roofs, low-pitch roofs, garden buildings, porches, and garages are among the most common structures where felt is installed, but it’s also used on extensions and commercial premises where quick, cost-effective waterproofing is needed.
There are several types of felt available for installation, each with its own advantages. Traditional bitumen-based felt, which requires torch-on application, is a staple in professional roofing. It’s reliable and long-lasting when applied by a trained roofer with the right tools and experience. Torch-on felt bonds to the substrate via melted bitumen, forming a watertight seal that’s hard to beat. It typically requires a gas torch, a heat-safe work area, and good weather conditions for safe installation.
Self-adhesive roofing felt, often referred to as peel-and-stick felt, is another popular choice—especially for smaller jobs or flame-free environments. It allows for clean, simple application without the need for torches or hot bitumen. It’s ideal for sheds, garages, or outbuildings and can also be used as part of a layered system on larger roofs. Installation is quicker and safer, making it a top pick for both experienced tradespeople and confident DIYers.
Another option is pour-and-roll felt, which uses cold or hot bitumen as an adhesive. This older method is still used on some larger or more traditional roofing jobs and can be effective when done properly, but it’s generally more labour-intensive and requires more equipment.
Before starting a felt roof installation, surface preparation is critical. The substrate must be dry, clean, solid, and smooth. OSB or marine plywood are often used as the base for flat roofs. Any dampness, dust, or imperfections in the deck can compromise the adhesion of the felt and lead to issues later on, such as bubbling, lifting, or leaks. In colder months, installations should be planned around dry days and mild temperatures to ensure the felt seals properly.
For most flat roof installations, the process begins with the application of an underlay felt, which acts as the first line of waterproofing. This layer is either nailed, torched, or self-adhered, depending on the system being used. A second cap sheet is then applied on top, featuring a mineral finish to protect the bitumen from the sun and increase overall lifespan. In three-layer systems, a venting layer may be added between the underlay and cap sheet to allow moisture to escape from the deck and prevent condensation buildup.
Overlap at joints and seams is one of the most critical aspects of a felt roof installation. Joints must be sealed tightly, usually with bitumen adhesive, torching, or self-adhesive bonding, depending on the product. Poorly sealed joints are one of the most common causes of premature roof failure. Flashings and upstands—where the roof meets walls or other surfaces—should also be carefully detailed and reinforced to prevent water ingress.
Felt roofing systems also need to consider drainage. Flat roofs should still have a slight gradient (usually between 1:40 to 1:80) to encourage water runoff. Standing water can reduce the lifespan of felt roofing and lead to sagging or leaks. Installing roof edge trims and ensuring proper guttering is in place can help direct water away from the roof effectively.
One of the key advantages of felt roofs is their affordability. Compared to rubber membranes or GRP systems, felt roofing provides a cost-effective solution for flat roof waterproofing without compromising performance. High-quality felt products installed correctly can last upwards of 20 years, and with minimal maintenance, some even reach 30 years or more.
Maintenance of a felt roof is relatively simple. Regular inspections should be carried out, especially after heavy rain or high winds, to check for tears, bubbling, or lifting edges. Minor repairs can be carried out with patches or cold adhesive sealants, and damaged sections can be replaced without the need to strip the entire roof. This flexibility makes felt roofs particularly appealing to property owners and landlords who need reliable performance with low upkeep.
Felt roofing also has the benefit of being lightweight, which is crucial for outbuildings, timber-framed structures, and flat roofs that can’t bear excessive loads. Its compatibility with insulation boards, breather membranes, and vapour control layers also makes it a good fit for energy-efficient roofing designs.
When it comes to choosing the right felt, always consider the environment, structure, and use of the building. For example, mineral-finished top felts are better suited to exposed roofs and will protect the roof from UV degradation. Torch-on cap sheets are preferred for professional builds, while self-adhesive felt is ideal for domestic projects or areas where flame use is restricted. Heavy-duty felts with reinforced layers offer superior resistance to tearing and weather fatigue, making them suitable for high-traffic or exposed locations.
Installing a felt roof isn’t just about the materials—it’s about the process, too. Whether you’re laying felt on a garden shed in a single afternoon or completing a full flat roof installation on a residential property, care and attention to detail are everything. Following the correct steps, using the right adhesives, ensuring adequate overlap, and choosing the appropriate product for the job are what make the difference between a roof that lasts a few years and one that lasts decades.
In a professional setting, felt roofs are also used for insurance jobs, emergency repairs, and temporary coverings. Their flexibility, speed of application, and availability in different roll sizes make them ideal for urgent callouts and quick fixes when weather damage strikes. Commercial roofing contractors often carry rolls of felt and accessories in their vans to address water ingress quickly and cost-effectively.
Ultimately, felt roof installations remain one of the most versatile and cost-efficient solutions in the roofing industry today. Whether for domestic or commercial use, new builds or repairs, temporary solutions or permanent structures, felt roofing—when installed properly—offers outstanding protection, minimal disruption, and exceptional value for money. It’s no surprise that despite all the new technologies and systems available, felt roofing continues to be trusted by roofing professionals across the UK.
If you’re planning a felt roof installation and need help choosing the right product or installation method, speak to a local expert or specialist roofing supplier. Getting the right advice at the start ensures your installation is compliant, long-lasting, and perfectly suited to the building it’s designed to protect.
FAQ: Felt Roof Installation
- What is a felt roof?
A felt roof is a waterproof roofing system made by applying layers of bitumen-based felt to a roof deck. It’s one of the most commonly used roofing methods for flat and low-pitched roofs across the UK. Modern felt roofs can be installed using torch-on, self-adhesive, or cold-applied techniques, offering flexibility for different structures and installer preferences.
2. How long does a felt roof last?
When installed correctly and maintained well, a felt roof can last anywhere from 15 to 30 years. The exact lifespan depends on the quality of the materials used, the installation method, exposure to the elements, and ongoing upkeep. Multi-layer systems with high-performance cap sheets tend to last longer than single-layer installations.
3. What buildings are best suited to felt roofing?
Felt roofing is ideal for flat or low-pitched roofs on sheds, garages, porches, extensions, workshops, outbuildings, and some commercial or industrial premises. It’s a cost-effective solution for domestic properties and is often used for both temporary and permanent roofing in residential and trade environments.
4. What types of felt are available for installation?
The main types include torch-on felt (applied using a gas torch), self-adhesive felt (peel-and-stick), and pour-and-roll felt (used with cold or hot bitumen). Each type has unique benefits depending on the job, with self-adhesive being the safest and most DIY-friendly, while torch-on offers the most robust, professional-grade finish.
5. What’s the difference between underlay and cap sheet?
Underlay felt forms the base waterproofing layer, while the cap sheet acts as the final, weather-exposed layer. The cap sheet typically includes a mineral finish to protect against UV rays and physical wear. In multi-layer systems, these two work together to provide a long-lasting, sealed, and resilient surface.
6. Do I need planning permission to install a felt roof?
Generally, felt roofing repairs or replacements on existing structures do not require planning permission. However, if you’re adding height, changing the roofline significantly, or working on a listed building, it’s best to consult your local planning authority. Always comply with Building Regulations regarding insulation and drainage where applicable.
7. How much does felt roofing cost?
Felt roofing is one of the most affordable systems in the UK, with costs varying depending on the size of the roof, the type of felt used, access conditions, and whether it’s a repair or full replacement. Expect to pay more for torch-on systems due to the labour involved and specialist equipment needed, while self-adhesive or shed felt rolls are more cost-effective for small jobs.
8. How is felt roofing installed?
Installation typically involves cleaning and prepping the roof deck, applying a primer (if needed), rolling out the underlay felt with overlap joints, sealing joints with adhesive or torch heat, and then adding the cap sheet. Edges are sealed, drip trims installed, and ventilation points considered to prevent condensation. Different methods (torch-on vs. self-adhesive) have their own specific steps.
9. Can I install a felt roof myself?
Yes, for small projects like sheds or garages, self-adhesive felt or nail-on mineral felt is very DIY-friendly. However, larger or more exposed roofs should be installed by professionals, especially if using a torch-on system, which involves flame and health and safety compliance.
10. Is torch-on felt dangerous to install?
When installed by trained professionals using the correct safety protocols, torch-on felt is safe and effective. It should never be used near flammable structures or by untrained individuals. In domestic settings or timber structures, self-adhesive or cold-applied systems may be a safer alternative.
11. Can a felt roof be repaired?
Yes. Felt roofs are easy to patch with compatible materials. Small tears, cracks, or lifted seams can be repaired with cold-applied bitumen and patch felt or adhesive repair strips. Larger issues may require partial or full replacement of one or more felt layers.
12. How do I maintain a felt roof?
Inspect it twice yearly (spring and autumn) and after major storms. Look for bubbling, tears, lifting at the edges, and ponding water. Keep gutters clear and trim overhanging branches. Address any damage quickly to prevent water ingress and deterioration.
13. What’s the best time of year to install felt roofing?
Installations are best done in mild, dry weather. Spring, summer, and early autumn are ideal. Cold weather can reduce adhesive effectiveness, while wet weather can trap moisture and compromise the bond between the felt and the deck.
14. Can I felt over an existing felt roof?
Yes, as long as the existing roof is dry, structurally sound, and not suffering from trapped moisture or extensive damage. Overboarding or overlaying can be a cost-effective way to extend roof life without full removal, but should only be done under expert advice.
15. Is felt roofing environmentally friendly?
Felt roofing is made from bitumen, a petroleum-based product, so it’s not inherently eco-friendly. However, its long lifespan and the option to repair rather than replace make it a more sustainable option compared to single-use or low-durability materials. Disposal must be handled correctly through approved waste channels.
16. ow does felt compare to EPDM or GRP?
Felt is more affordable and easier to repair but typically has a shorter lifespan than EPDM (rubber) or GRP (fibreglass). EPDM is extremely long-lasting and UV resistant, while GRP offers a seamless, rigid finish. Felt is more flexible, budget-friendly, and suitable for more complex roof shapes or quick repairs.
17. Does a felt roof need ventilation?
Yes. Proper ventilation is essential for flat roofs to prevent condensation buildup, which can damage timber decks and insulation. Breathable membranes, vapour control layers, and ventilated upstands help manage moisture beneath the surface.
18. Can I insulate a felt roof?
Absolutely. Flat roofs can be insulated above (warm roof) or below (cold roof) the deck. Warm roof systems place insulation above the structural deck and below the felt, helping reduce heat loss and prevent condensation. Warm roofs are more efficient but may raise the height of the roofline.
19. How long does installation take?
Small shed or garage roofs can often be completed in a few hours. Larger domestic or commercial flat roofs may take one to three days depending on size, weather, and access. Multi-layer systems take longer but offer increased durability and performance.
20. Can felt roofs be used in commercial settings?
Yes, felt roofing systems are widely used on schools, warehouses, retail units, and office buildings. Torch-on systems in particular are ideal for large, flat commercial roofs due to their strength, weather resistance, and longevity.
21. What guarantees come with a felt roof?
Most manufacturers offer warranties ranging from 10 to 20 years depending on the product type and installation method. When installed by an accredited contractor, you may also receive an insurance-backed workmanship guarantee. Always ask for warranty documentation upon completion.
22. Do I need drip edges or roof trims with a felt roof?
Yes, trims help direct water into gutters and prevent water from running down walls or into the substrate. Drip edges also protect the edges of the felt from lifting due to wind or rain and give a clean, finished look to the roof perimeter.
23. Will felt roofing protect against heavy rain and snow?
Yes, properly installed felt is fully waterproof and built to withstand the UK’s harsh weather. Mineral-finished top layers protect against UV and snow load, while sealed overlaps and joints stop water ingress. Regular inspections ensure long-term performance during heavy winters or rainy spells.
Matthew Phillips 
