Is Roofing Felt Flammable? (How to Test if it’s Combustible or Not)

We all know that there’s a lot of stuff that’s flammable, and some of it is pretty surprising. But what about roofing felt? How can you tell if it’s combustible or not?

This article will explain what roofing felt is and what makes it flammable. It will also cover different types of roofing felt, their properties, and how to test for combustibility.

Is roofing felt flammable?

Yes, roofing felt is flammable. Roofing felt is typically made of asphalt-saturated organic materials such as paper or fiberglass, making it combustible.

The American Society for Testing and Materials classifies roofing felt as having a flame spread rating of 25 or less, meaning it will burn readily when exposed to an ignition source.

The flammability of roofing felt is a concern because it is often used as an underlayment for roofing materials, which means it is positioned directly beneath the roof covering.

In the event of a fire, roofing felt can help to spread the flames quickly, making it more difficult for firefighters to contain and extinguish the fire.

For this reason, roofing felt manufacturers typically include fire resistance ratings in their product descriptions to help to build owners and contractors make informed decisions about the safety of their roofing systems.

To further reduce the risk of fire, building codes may require the use of fire-resistant roofing felt, particularly in areas with a high risk of fire such as wildfire-prone regions.

Table: Types of roofing felt vs flammability and the Flame Spread Rating*

Type of Roofing FeltFlammabilityFlame Spread Rating
Asphalt feltFlammable26-75
Tar paperHighly flammable76-200
Mineral feltFlammable26-75
Fire-resistant feltFire-resistant0-25
Synthetic feltMost are fire-resistant0-25
Metal feltHighly fire-resistant0-25
Wood shingle underlaymentFlammable76-200
Tile underlaymentFire-resistant0-25
Flame retardant EPDMFire-resistant0-25
*This is a table that lists some of the major types of roofing felt, their flammability, and their flame spread rating, sometimes known as the flame spread index. The higher the flame spread rating (FSR), the less fire-resistant they are. Caution: studies and analyses of FSI should not be taken as facts. These are merely estimations, and situations may vary. Talk to your local professionals about what’s best to use. No underlayment is fireproof.

The flame spread rating is a measurement of how fast and how far the flame travels in 10 minutes. The distance is captured and the material is put into categories of 0-25 which are considered Class A, 26-75 which is Class B, and 76-200 which is Class C. Class A is considered fire-resistant, Class B is somewhat flammable, while Class C is considered flammable.

Types of roofing felt and whether they are flammable?

Asphalt felt

Asphalt felt is made of organic materials that have been saturated with asphalt. It is a common and cost-effective option for roofing underlayment but is also flammable.

Mineral felt

Mineral felt is made of asphalt-saturated glass fibers. It is more durable and less likely to catch fire than organic asphalt felt, but it can still catch fire.

Fire-resistant felt

Fire-resistant felt is a type of roofing underlayment that is designed to be less flammable and slow the spread of fire. This type of felt is typically made of a blend of inorganic materials, such as fiberglass and mineral-filled asphalt.

Synthetic felt

Synthetic felt is made of synthetic fibers such as polyethylene or polypropylene. It is lightweight, easy to install, and water-resistant, but it will shrivel up when exposed to flame.

Metal felt

Metal felt is a roofing underlayment made of metal sheets, typically aluminum or copper. It doesn’t catch fire easily and is used in places where there is a high risk of fire, like places where wildfires happen often.

Wood shingle underlayment

Wood shingle underlayment is a type of roofing felt that is designed to be used beneath wood shingles. It is typically made of organic materials, making it flammable.

Tile underlayment

Tile underlayment is a type of roofing underlayment designed to be used beneath tile roofing. It is typically made of either fiber-reinforced asphalt or synthetic materials and is often fire-resistant.

How to test if roofing felt is combustible

To test if roofing felt is combustible, follow these steps:

  1. Obtain a sample of the roofing felt you want to test. Make sure the sample is representative of the felt you will be using for your roofing project.
  2. Gather materials for the test: a lighter, a metal container (such as a metal can or tin), and a fire extinguisher.
  3. Place the roofing felt sample in the metal container.
  4. Light the roofing felt sample with the lighter.
  5. Observe the roofing felt sample as it burns. If it ignites and burns readily, it is considered to be combustible.
  6. Extinguish the burning roofing felt sample immediately with the fire extinguisher.
  7. Record your observations, including the time it took for the roofing felt sample to ignite and the time it took to extinguish the fire.

It’s important to remember that even if the roofing felt sample passes the combustibility test, it still needs to meet the fire-resistance requirements specified by local building codes and fire regulations.

Tests like these should always be done in a safe, controlled environment, and a fire extinguisher should always be close by in case of an emergency.

What factors should you consider when looking for fire-resistant roofing felt?

When looking for fire-resistant roofing felt, consider the materials used to make the felt, the fire rating, and the local building codes and fire regulations.


The materials used to make the roofing felt can greatly impact its fire resistance.

Look for roofing felt that is made of inorganic materials, such as fiberglass and mineral-filled asphalt, as these materials are less flammable than organic materials, such as paper or fiberglass.

Fire rating

Look for roofing felt that has been tested and certified for its fire resistance. The most common fire rating for roofing felt is Class A, which is the highest fire resistance rating.

The fire rating will tell you how well the roofing felt can stop a fire from spreading and how much damage it can take.

Local building codes and fire regulations

Make sure the roofing felt you choose meets the fire-resistance requirements set by your local building codes and fire regulations.

This will make sure that the roofing felt you choose is good for your area and will protect your home well if it catches on fire.


Thicker roofing felt generally provides better fire resistance than thinner felt. This is because thicker felt has more material to slow down the spread of fire.


The way the roofing felt is installed can also impact its fire resistance. For example, a fire is less likely to spread if the felt is installed tightly and with the right overlap.


Fire-resistant roofing felt can be more expensive than regular roofing felt, but it’s important to think about the long-term benefits and possible cost savings that come from preventing fire damage.

Brand reputation

Choose a reputable brand that is known for producing high-quality, fire-resistant roofing felt. Research the brand’s history and read customer reviews to get a better understanding of the brand’s product quality and customer satisfaction.

How often do roof fires start from roofing felt?

Roof fires caused by roofing felt aren’t very common, but it’s hard to say how often they happen.

Roof fires can be caused by various factors, such as sparks from nearby fires, lightning strikes, or faulty electrical wiring. The use of fire-resistant roofing felt can help reduce the risk of fire, but it is not a guarantee that a fire will not start on the roof.

While roofing felt itself may not be the direct cause of a roof fire, it can contribute to the spread of fire if it is not fire-resistant or is not installed correctly. Choose fire-resistant roofing felt and have it installed by a professional to ensure the best protection against fire damage.

How can I prevent my roofing felt from catching fire?

  • To prevent roofing felt from catching fire, you should use fire-resistant roofing felt and have it installed properly by a professional.
  • Keeping the area around your roof clear of combustible materials, such as dry leaves and branches.
  • Performing regular maintenance on any electrical wiring and appliances on your roof to reduce the risk of electrical fires.
  • Installing lightning rods or other lightning protection systems to protect your roof from lightning strikes
  • Having chimneys, flues, and vents inspected regularly to ensure they are functioning properly and not creating a fire hazard
  • Have your roof inspected regularly to identify any potential fire hazards and to ensure that your roofing felt is in good condition and functioning properly.
  • Proper ventilation helps to reduce the risk of fire by removing heat and moisture from your attic, which can cause the temperature in your attic to increase and increase the risk of fire.
  • Keep your roof and gutters free of debris, such as leaves and twigs, which can create a fire hazard. Clean your roof and gutters regularly to reduce the risk of fire.
  • Consider installing fire sprinklers on your roof to help suppress fires and minimize damage in the event of a fire.

What materials in roofing felt make it flammable?

Roofing felt can be flammable due to the presence of natural materials like wood cellulose as well as synthetic materials like fiberglass and polyester.

Bitumen, a type of asphalt, is often used as a coating in roofing felt, which can also contribute to its flammability.

The cellulose fibers used in some types of roofing felt can ignite and burn readily, while synthetic materials can melt and contribute to the spread of fire.

Choose roofing felt that is treated with fire-resistant chemicals or made from fire-resistant materials in order to reduce the risk of roof fires.

Can the sun cause roofing felt to catch fire?

Yes, the sun can cause roofing felt to catch fire under certain conditions. The intense heat from the sun can cause the temperature on a roof to rise significantly, especially on dark-colored roofs or in areas with high temperatures.

If the roofing felt is exposed to direct sunlight for long periods of time, it can become hot enough to ignite, especially if it is made from flammable materials.

This is why it is important to choose roofing felt that is treated with fire-resistant chemicals or made from fire-resistant materials to reduce the risk of roof fires.

To keep the roof from getting too hot, it’s best to take precautions like providing shade or airflow.

What to do when roofing felt catches fire?

Roofing felt usually starts to burn at around 500 degrees Fahrenheit, so it is rare for it to catch fire from direct sunlight.

However, if the roofing felt is exposed to direct sunlight for long periods of time and if the roof is old enough, it can become hot enough to ignite, especially if it is made from flammable materials.

What is the fire classification of roofing felt?

The fire resistance of roofing felt is used to classify it. Different classifications show how well it protects against fire.

The most common fire classifications for roofing felt are Class A, Class B, and Class C. Class A roofing felt provides the highest level of fire resistance, with Classes B and C providing lower levels of fire protection.

Roofing felt can have different fire ratings depending on the type of material used, how it was made, and what kind of fire-resistant treatment it has been given.

Consider the fire classification when choosing roofing felt, and choose a product that gives you the right level of fire protection for your needs.

What are some less-flammable alternatives to roofing felt?

Fire-resistant felt, fiberglass mats, and synthetic underlayment are less flammable alternatives to roofing felt.

  • Fire-resistant felt is made with a blend of asphalt and fire-retardant chemicals that make it more resistant to ignition.
  • Fiberglass mat is made from glass fibers and is treated with fire-retardant chemicals to make it less flammable.
  • Synthetic underlayment is made from polyethylene or polypropylene, which are not flammable and are known for their strength and durability.

These materials give homeowners an option that is safer and less likely to catch fire. This reduces the chance of roof fires and makes the roof safer overall.

Other interesting articles:

Author: Logan

I help people connect with businesses