Is roofing-felt biodegradable? (3 types of roofing felt)

This article is focused on answering the question of the biodegradability of roofing felt.

It will also cover other related areas such as:

  • Types of roofing felt.
  • Composition of roofing felts.
  • The biodegradation process.

Is roofing-felt biodegradable?

No, roofing felt is non-biodegradable because it is made up of components that can not be broken down by microorganisms such as bacteria and fungi.

Today, roofing felt is made mostly of bitumen and synthetic polymers such as fiberglass or polyester. These materials are resistant to microbial degradation.

Initially, roofing felt was made using natural, organic polymers such as cellulose, rag fiber, and hessian. These polymers are hardly used nowadays, and the preference has shifted to polyester, due to its ready availability, and cheap market prices.

Roofing-felt made from the aforementioned organic polymers was biodegradable because organic materials are susceptible to microbial degradation.

The process of biodegradation is a complex one that uses different agents and is affected by different factors. 

Biodegradation is the process by which microorganisms such as bacteria and fungi break down organic tissue into small biomass, producing carbon dioxide, water, or methane.

Heat is also produced during the process of biodegradation and is lost to the environment. 

The main agents of biodegradation are bacteria and fungi. They break organic materials, using them as a source of carbon to make food and energy.

Microbes can use either oxygen or other chemical compounds to break down organic matter. When they use oxygen, the process is called aerobic biodegradation.

When microorganisms use any other chemical to break down organic matter instead of oxygen, the process is called anaerobic biodegradation.

The products of aerobic biodegradation are carbon dioxide and water. The products of anaerobic biodegradation are carbon dioxide and methane.

The biodegradation process occurs in three distinct stages: biodeterioration, bio-fragmentation, and finally assimilation. 

Biodeterioration is the first stage of biodegradation that involves abiotic factors such as light, UV radiation, and water to help in the weakening of the structure of organic substances.

Bio-fragmentation is the second stage that involves the physical breakdown of organic matter into small particles, this is due to the biodeterioration of the organic matter in the first stage.

The last stage involves the fungi and the bacteria breaking down the small particles into even smaller biomass, producing heat, water, carbon dioxide, and methane, with the products depending on the type of biodegradation; whether aerobic or anaerobic.

What is roofing-felt made up of?

Roofing felt is a base material used to make roof shingles and roll roofing. The base is mainly made up of polymers such as polyester or fiberglass and covered with a membrane of bitumen.

Roofing felt can be categorized in various ways depending on the use of physical properties.

There are generally three types of roofing felt; they include:

  • Torch-on felt.
  • Self-adhesive felt.
  • Shed-felt.

Torch-on felt.

This type of roofing involves three layers of bitumen felt. The felt is applied by being rolled out on the roof and a blowtorch is used to heat and melt the felt. 

The melting layer of the felt welds the felt to the roof. This forms an impermeable layer between the roof and the felt.

The advantages of torch-on felt roofs include:

  • The felt forms a resilient and water-tight cover on the roof. This ensures that felt stays intact even through adverse weather conditions such as strong winds.

It also protects the roof from water penetration which may interfere with the integrity of the roof.

  • It is easy to install, albeit by professionals. The process of laying felt roofing is simpler than other roofing. It is just like rolling a carpet on the floor. The challenge comes with using the torch, which requires people conversant with the process.
  • It is strong and very durable. The torch-on felt is also resistant to UV radiation and heat. 

When melted, the felt bonds strongly to the roof, making it resistant to adverse weather conditions like strong winds.

  • It is versatile. Once the felt is melted, it becomes malleable and can easily be shaped into different designs to cover roofs of different shapes.

It is also easy to repair because it involves cutting a piece of felt and repairing a certain point.

  • It contains a long-term value for money. Torch-on felt lies in the middle of very expensive roofing materials and cheap roofing materials.

Since it is resistant to conditions such as heat, and adverse weather conditions, it is highly durable and requires little maintenance. This makes it a valuable roofing material.

The advantages of torch-on felt include:

  • The installation process may pose the threat of fire hazards. The use of a blow torch may start a fire, although the chances are very low. 

The installation process should involve a qualified person to address this risk.

  • It has a shorter lifespan compared to other alternatives. Torch-on felt sits in the middle of roofing materials. There are those which are cheaper, and therefore less durable, and there are those which are more expensive than torch-on felt, and therefore, are more durable. The choice depends on the person.
  • The repairs of torch-on felt may look a little shambolic. Repairing the torch-on felt involves using patches to repair specific areas, this makes the roof have patches, something not very appealing to the eyes.
  • Torch-on felt is not exactly a DIY project. The installation of torch-on felt requires experienced experts to prevent damage and the risk of starting a fire using the blowing torch.

Self-adhesive felt.

This involves the use of roofing felt that contains its adhesive.

The roofing felt is good for the DIY installation because, unlike the torch-on felt, it doesn’t involve the use of any flames or any complicated gadget.

It involves the peeling off of the film on the felt to expose the adhesive, then the felt bonds with the roof.


This type of roofing felt is suitable for sheds and garden structures.

It can come either as a torch-on felt or as self-adhesive felt. It is waterproof and resistant to adverse weather conditions and therefore suitable for garden structures.

What are the signs of aging roofing felt?

Roofing felt can go for up to 30 years, depending on the material, installation process, and weather conditions.

The aging roofing felt will show using several changes in its structure, such changes include:

  • Felt roof tears and cracks: These are the easiest changes to observe in roofing felt. 

The changes are a result of weather damage or an over-aged roof. Small tears and cracks can be easily repaired, but a split across the entire felt surface requires a replacement of the entire roofing felt.

  • Bubbling and blistering in roofing felt: This comes as a result of the adhesive failing to bond well the felt base with the roof.

Blistering can be repaired when discovered early, but when blisters become big, the whole roofing felt ought to be replaced.

If a blister pops or ‘bursts’, it creates a hole on the roof which leads to water penetrating the roof and destroying it.

  • Ponding on roof felt: This involves water accumulating on the roof. Water causes stress to the roof, leading to cracking and water penetration.
  • Organic growth: The growth of algae and moss might signify the accumulation of water on the roof, this might be putting your roof at the risk of cracking and letting water penetrate the roof.

What is the difference between number 15 and number 30 roof felt?

This is a physical property of roof felts. It is a difference in the thickness of the roof felt. 

According to an article, Number 30 roof felt contains a thicker layer of underlayment than the number 15 felt, and it, therefore, is more suitable for flat roofs that will most likely accumulate water.

Number 15 roof felt is more suitable for steep roofs because rainwater will run off the surface faster.


This blog article has addressed the question of the biodegradability of roofing-felt.

It has also covered some other areas such as:

  • Components of roofing felt.
  • Types of roofing felt.
  • Advantages of roofing felt.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is roofing felt biodegradable?

Does roofing-felt degrade?

Yes, roofing felt is exposed to UV radiation, heat from the sun, and other adverse conditions, as a result, it will crack, break down into small pieces, and get depleted after some years and may need replacement.

Is felt bad for the environment?

Roofing felt contains synthetic polymers such as polyester and fiberglass which are non-biodegradable. It breaks down over time into small pieces which will eventually accumulate in the environment, on land and water bodies, causing pollution.

What is roofing felt made of?

Roofing felt is made up of bitumen and underlayment of either fiberglass or polyester. 


An article on MyTrustedExpert on Torch-on felt. Torch-on Felt Roofing: Advantages And Disadvantages.

Retrieved from:,welding%20it%20to%20the%20roof

Bourbigot, Serge; Cerin, Oriane; Duquesne, Sophie; Clavel, Norbert (1 March 2013). “Flame Retardancy of Bitumen: A Calorimetry Study”. Journal of Fire Sciences. 31 (2): 126. doi:10.1177/0734904112458240. 

Brown, AB; Sparks, JW (1960). “Composition and Rheology of Roofing Asphalt”. Symposium on Bituminous Waterproofing and Roofing Materials. pp. 3–17. doi:10.1520/stp38450s

Leave a Comment