Roofing Felt and Why It's Important | Gilstrap Roofing

January 29, 2020

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Have you ever driven by a roofing job in your neighborhood and noticed the black paper on the roof before the shingles were applied? Roofing felt or felt paper, also called underlayment or roofing tar paper, goes between the roof deck and the shingles, which adds another layer of protection to your roof.

Underlayment has a base made from natural materials like wood cellulose, or synthetics like fiberglass/polyester. Then it is covered with a protective asphalt coating, known as bitumen. The felt paper repels water and still allows it to breathe.

Professional roofers know that by adding a layer of protection between the wood and the shingles not only serves aesthetic purposes but extends the life of your roofing. The underlayment serves several purposes:

It serves as a water repellent when heavy rain and storms can cause moisture to get trapped between the shingle and wood of your roof decking. Humidity is terrible news for any roof causing water damage, leaks, or even mold. The felt helps keep water away from the wood, so it doesn’t leak into your attic and home.

Roofing felt can be a life-saver during extreme storms, heavy rains, and snow. Even if you lose a shingle, the felt provides an extra layer of protection for the roof deck. The underlayment continues to form a line of defense for your roof should a shingle come loose.

For those living in areas where there is a lot of snow and ice, which can cause ice dams on roofs, it prevents water from building up and seeping through onto the wood decking. Ice or snow dams are hard on roofs because once the water gets trapped, it has to go somewhere when it begins to melt, and after sitting on top of your roof, it can only go down and attack the wood. The felt forms a powerful barrier preventing melting ice/snow from getting into your insulation, or worse, drywall ceilings.

Roofing tar paper can increase the fire rating for your roof, which can result in lower insurance rates if you have a roof without it. The additional layer can yield a Class A fire rating. When roof shingles are rated, they are done so with felt underneath. By themselves, your particular shingles may not pass the Class A fire rating. Professional roofing companies choose a base that is a match with your specific shingle. Be sure to ask your roofer about the grade of your shingles and the felt paper they use. ASTM International is standard compliance.

Ever noticed a new home that sits for a week, two, or even three before the roofers arrive to apply the shingles? If there is a lot of rain, snow, ice, or high winds during that period, the wood deck can be damaged. Felt roofing paper offers a layer of protection during this period before the shingles are secured. You don’t want to risk wood rot, moisture, or mold on a new roof before shingles are secured.

This extra layer helps shingles lay flat by providing an even surface for the shingles to lay flat. Roof decking is not always uniform as it can have slight imperfections from the lumber yard. The smallest notch or bump can cause a shingle to set up, or sink. The underlayment helps the shingles bind to a flat, even surface, which causes uniformity with fewer abnormalities.