Roof structures are complex with lots of layers. Roof felt might just seem like an unnecessary extra, but it’s important to keep your home warm and dry. So, if you’re wondering how the pros use felt in roofing, read on.
What is Roof Felt and What is It Used For?
Moisture is a big problem for buildings. When water gets in, it gets trapped. And it damages the wooden roof structure, leading to decay, which is an even bigger problem. Structural damage ensues.
But there are several protective shields professionals use to keep the inside of your home safe from dreaded water.
Roof felt is one such shield. Underlay (as it’s also called) is a protective layer between the roof deck and the shingles or tiles on top, keeping the inside dry from moisture and wind. It’s an extra barrier against leaks and water damage.
Different Types of Roofing Felt Materials
There are several kinds of roof felt. These are categorised by the application method or the base material. Synthetics are generally stronger and more durable, but can be more expensive than original felts.
Felts By Application Method
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Torch-on felt is a durable and reliable option for flat roofs. Apply the felt by melting bitumen with a blowtorch for a waterproof seal.
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Self-adhesive felt is easy for DIY applications and more convenient than torch-on felt.
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Shed felt is designed for garden buildings, like sheds. It’s an economical choice, although it might not last as long as other kinds.
Felts By Base Material
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Traditional organic fabric is made from natural materials, like wood fibre or jute. It’s affordable but might not last long as it’s more susceptible to absorbing moisture.
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Modern synthetic felt is made from materials like fibreglass and polyester. They’re known for their strength and resilience.
Do You Need Roof Felt?
Yes. Roof felt or a similar underlay is a vital layer to protect against moisture damage, wind, snow, and any other extreme outside weather conditions. Why is it so important? Well, without it, you might find yourself replacing your other roof materials and structure long before you hoped.
Benefits of Using Roof Felt
Roofing felt can extend the lifespan of your home’s roof structure. How? There are plenty of reasons to use roof felt, and your home will thank you for it.
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Felt creates a waterproof barrier to prevent water and snow from seeping inside, leading to rot and mould
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The roof felt acts as a permeable barrier that allows warm, moist air to escape from inside the building to prevent dampness inside
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Felt shields the roof from strong winds that can dislodge roof shingles and create leaks
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By protecting the roof structure, felt helps to improve the longevity of your roof materials, and the life of the building itself
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Roof felt is a cost-effective and affordable material
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The installation process is easy, and repairs are often simple
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Roof felt offers a degree of sound dampening, which insulates against noise from outside
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Roof felt can prevent pests from entering your home
Common Issues with Roof Felt
Nothing is perfect. Here are the common issues professionals face with felt in roofing:
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UV radiation, temperature fluctuations, and age can make the felt vulnerable to cracking, which allows water to penetrate
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Air or moisture can get trapped beneath the felt layers during the installation process, weakening the felt and making leaks more likely
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Poor drainage on a flat roof can allow water to pool and cause sagging or soft spots in the roof
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Fallen branches or other debris can puncture the felt and lead to leaks
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Felt has a limited lifespan – typically lasting 10-20 years – and naturally degrades over time
How To Install Roof Felt
Different roof felts require different methods – and some are more complex than others. For instance, torch-on felt requires a blow torch and a degree of expertise (plus safety equipment). If you’re planning on DIY-ing your roof felt application, it’s best to use self-adhesive felt.
Step-by-step guide to installing roof felt:
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Installing roof felt requires a clean roof surface. Use a power washer or a brush to clear your roof of debris and dirt.
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Roll out the felt with a slight overhand.
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Secure the felt with large-headed clout nails, working from the centre and overlapping each layer.
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Apply adhesive to the overlaps to create a watertight seal.
How Do You Maintain Roof Felt?
Roof felt might only last between 10-20 years, but you can ensure you maximise its lifespan with regular checks to inspect for damage and clear debris.
The biggest danger to your roof felt – and your roof structure more generally – is water. So, to maintain your roof felt, you need to keep it clear of moisture building up. This means unclogging your gutters and repairing cracks. You can also apply protective coatings to add an extra waterproof layer.
How often do you need to inspect your roof? Aim for twice a year. Autumn and spring are good times, as well as after particularly severe weather.
Final Thoughts on Roof Felt
Roof felt is a key part of your roof structure. The pros might use the more complex to install torch-on felt, but DIY-ers can easily install self-adhesive felt. And it’s a good idea to include an underlay on your roofing system to prolong the lifespan of your home. Check up on your felt and other roofing materials regularly to ensure it’s in good shape.
FAQs
What is Roofing Felt Roof Made Of?
Roofing felt can be organic or synthetic. Traditional organic felt is made from natural materials, like wood fibre or jute. Synthetic roofing underlayment (like asphalt-saturated felt) is made of a fibrous membrane and coated with bitumen for waterproofing purposes.
How Long Does Roofing Felt Last?
Roofing felt typically lasts between 15 and 20 years. That said, poorly installed felt might only make it five years before needing replacement, while well looked-after underlayment can reach 30 years or more. The materials, installation, type of roof, maintenance, and exposure to weather can all affect the lifespan of roofing felt.
Does Roof Felt Stop Leaks?
Yes. Roof felt adds a protective layer between the roof shingles and the rest of the roof structure. This prevents unwanted moisture from finding its way inside. It can also work as a temporary waterproof shield to protect your home if you find a missing roof tile or damage.