Dream Lands Design
You're here: Home » Home Improvement » What is Roofing Felt?

What is Roofing Felt?

Everyone knows that their roof is one of the most important – if not the most important parts of their home. And in the same breath, most homeowners know the key elements of their roof and their importance.

We’re referring to the gutters, soffit and fascia, eavestrough, and even the flashing.

image -  What is Roofing Felt?
What is Roofing Felt?

But there is one part of the roofing system that people do not know much about. It seems insignificant but ensures the roof can function as it should. It’s the roofing felt.

And we’re going to explain the importance of this little section.

Your Guide to Roofing Felt

What is Roofing Felt?

Also known as tar paper, roofing felt is the thin layer of material (either natural, such as wood, or synthetic, such as fiberglass) that is installed between the roof deck and the shingles.

In simple terms, roofing felt is an extra layer of protection for your home against external elements, such as weather or insects, while allowing your home to ventilate.

What are the Types of Roofing Felt?

As we mentioned above, there are two main types of roofing felt: natural and synthetic. In regards to the former, it refers to materials such as wood and cellulose.What are the Types of Roofing Felt?

In contrast, the latter refers to the likes of fiberglass, polyester, non-bitumen synthetic (known as synthetic underlayment), and rubberized asphalt underlayment.

While there are numerous types of materials, they usually come in two distinct sizes: No. 15 and No. 30.

What are the Differences Between No. 15 and No. 30?

Firstly, it’s important to understand the numbers. No. 15 and No. 30 refer to the weight of the felt: 15 pounds and 30 pounds per hundred square feet.

As to which one to use, it depends on the type of roofing material you’re using.

It’s best to use No. 15 when:

  • You use a single layer of roofing material (aka. Lighter projects)
  • Steeper pitched roofs
  • Ensuring you meet building requirements

It’s best to use No. 30 when:

  • The slope of the roof is between 2:12 and 4:12 (as they are more prone to rain collecting at the bottom)
  • You use one or two layers of thicker roofing material
  • For slate or tile shingles

Read Also:


Why is it Important?

There are several key reasons why you should get roofing felt like part of your roofing system:

  1. Resistant to water damage – The likes of heavy rainfall, melting snow, and trapped water can cause moisture damage, leaks, rot, and mold between the deck and your shingles. Felt will provide a level of protection against all water threats.
  2. Protection against ice dams – Melting ice dams can sneak into your home, causing extensive water damage. Felt will ensure it doesn’t happen in the first place.
  3. Extra protection against the weather – While your shingles are the main protection layer of protection for your roof, having another level below it can work wonders for your home in general.
  4. Stops insects & pests getting into the home – This layer of protection ensures that insects, critters, bugs, and pests cannot get into your home during the summer and winter months.
  5. Improve curb appeal and uniformity – Most roofs aren’t perfectly flat or straight but felt can help improve it. The extra layer of felt can give an even, uniform surface upon which you can install your shingles, improving your curb appeal and style.
  6. Increases home value – Buyers and investors look kindly to roofs that have an extra layer of protection, which means you can increase the value of your home when you install felt.

How Much Does It Cost?

It ultimately depends on the types of felt material you’re choosing, the weight, and the amount you need to cover your home. This little guide can help you:

  • ImproveNet says the natural average costs between “$0.39 per sq. ft. to $0.58 per sq. ft.”.
  • Remodeling Expense says that the total cost of basic roofing felt material is between “$165.00 – $175.00” while the “best” option is around $220.00 – $250.00.
  • HowTo mentions that the “average total cost per square meter is $4”

As you can see, the prices can range widely depending on the above-mentioned factors: size, weight, and amount. The best option is to speak to a roofing contractor directly to get an estimate.

We recommend speaking to Active Exteriors, Calgary’s leading roofing experts. They offer high-quality roofing workmanship for fantastic prices. Reach out and contact them today to get roofing felt installed!