Categories: BlogRoof Maintenance

What is the Purpose of Roofing Felt?

Most homeowners recognize the importance of their roof, but may not have heard of roofing felt. It’s a layer of tar paper that lines the top of your house before the roofing material goes on. Sometimes under the name roofing felt underlayment, its main function is to add extra protection from weather elements. Some people argue about whether or not roofing felt is necessary, given the durability of their roofing material and the added cost of roofing felt. You can certainly consider the factors surrounding your roof and what would be the best choice for you. We’ll outline the benefits of roofing felt and why you should consider pairing it with your roofing material for roof replacement. 

Types of Roofing Felt

There are three common types of roofing felt that are used:

  • Asphalt-saturated felt
  • Non-bitumen synthetic underlayment
  • Rubberized asphalt underlayment

Roofing felt typically comes in two sizes: No. 15 and No. 30, with No. 30 being the strongest. No. 15 should be used for lighter duty projects and steep roofs. It’s cheaper and can also be used short-term if something quick is needed. No. 30 is thicker and can be used with heavier duty projects, such as under slate or tile. You can buy a roll of roofing felt paper to cover your house; we recommend buying 10% more than you need. Asphalt-saturated felt is typically used, but it can depend on the roofing material and surface area. 

Why is Roofing Felt important?

In instances where harsh weather surrounds your home, roofing felt can be a lifesaver. If you live in a location known for heavy rain or high humidity, it’s not a bad idea to ensure you have roofing felt. Water can seep under your roofing shingles, which can leak into your home and cause lots of damage. If harsh storms tear shingles off your roof, it may be a few days to a few weeks before you get it repaired. In this situation, it’s critical to have roofing felt so that moisture doesn’t make its way into your home. Roofing felt’s main job is to waterproof the roof of your house; it provides an extra, cautionary layer of protection.

Fire Ratings

When your roofing material is inspected for fire ratings, it may need roofing felt paper in order to pass with a Class A Rating. Some shingles require the felt for safety reasons, as it acts as an extra shield between the fire and home. Make sure to research the type of roofing material you are placing on your home in conjunction with the roofing felt so that they are compatible and will achieve a high fire rating.


Another reason for installing roofing felt is the protection it provides against wood resin stains. It also can give a more uniform look to your roof, by presenting a smooth layer underneath your roofing material. It even acts as protection for roofing workers, who have to walk all over your roof. The felt gives them something to grip onto when they are taking shingles off or conducting any repairs. It’s more dangerous if there’s nothing beneath them when they’re removing roofing material.  

Even if you have a durable material that will rarely ever let moisture in, such as slate, it’s still a good idea to have roofing felt installed. It’s not very expensive and simply acts as another layer of protection on your home. Most people use asphalt shingles as their roofing material, which can definitely benefit from roofing felt. Asphalt tends to not last as long as other materials and has the potential to be easily damaged. We recommend installing roofing felt because it’s an easy extra step that could prevent damage and save you money down the line. 

Want to Learn More?

If you’re curious about how to install roofing felt, we can help you here at Perimeter Roofing. Our service technicians are a wonderful team of roofing experts ready to tackle roofing repairs and installations. Contact us to set up an appointment today at a Perimeter location near you. We serve states across the southeastern United States with quality roof repair, replacement, and maintenance.


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