Roofing felt is a paper-like material made of organic fibers and saturated with asphalt tar. It is available for purchase in large rolls. Common classifications of roofing felt used in new construction are 15-pound and 30-pound categories. This classification refers to the thickness of the material not the weight. For new construction, the thicker material is recommended for climates that have high levels of moisture or climates of extreme cold or heat. For most regions of the United States 15-pound roofing felt works well.
Measure the entire roof surface to determine the square footage. According to the International Roofing Group, a major manufacturer of roofing materials, a roll of 15-pound roofing felt covers approximately 430 square feet and a roll of 30-pound roofing felt covers approximately 200 square feet.
Apply a thin even layer of asphalt roofing cement about two inches wide along the edge of the roof line.
Start the first course of the roofing felt at the lowest edge of the roof. The manufacturer provides square corners on the material, but you should leave a few inches of overhang to insure good edge coverage. Press down the roofing felt onto the asphalt roofing cement.
Attach the roofing felt using a staple hammer and 3/8-inch or 1/2-inch staples. The staple hammer is more effective and efficient than a staple gun and uses the same staples. Work from left to right, stapling the roofing felt in a zig-zag pattern across the entire surface of the roofing felt. The staples should be 10 to 12 inches apart.
Start the next course of roofing felt by first applying asphalt roofing cement at the edge, work from left to right. Overlap the courses approximately 3 1/2 inches and staple in a zig-zag pattern every 10 to 12 inches.
Apply all additional courses as described previously, by first applying asphalt roofing cement and then stapling.
Apply asphalt cement at the ridge of the roof before applying the final overlapping course of roofing felt paper. Apply the roofing cement in a thin even layer for about four inches on each side of the roof ridge.
Cut and trim the roofing felt paper along the edge of the roof using a utility knife blade. Replace the blade often to insure an even and straight cut.