#15 Felt Paper
#15 felt paper is a traditional asphalt-saturated organic or fiberglass roofing underlayment that weighs approximately 15 pounds per square (100 sq ft), used as a secondary moisture barrier beneath shingles.
The Lightest Traditional Underlayment
#15 felt paper is the lightest grade of traditional asphalt-saturated roofing underlayment, weighing approximately 15 pounds per 100 square feet, used as a basic secondary moisture barrier between the roof deck and the shingles. For decades, #15 felt was the standard underlayment on residential roofs. It is still available and meets minimum code requirements in many areas, but it has largely been replaced by #30 felt and synthetic underlayment in professional practice.
On insurance claims, using the correct underlayment line item in the estimate matters for accurate pricing.
When #15 Felt Appears on Claims
Older homes that were last roofed 15 to 25 years ago may have #15 felt as the existing underlayment. On a replacement claim, the question becomes whether to replace with the same product or upgrade. If the current building code or shingle manufacturer requires a heavier underlayment, the replacement must meet that standard even if the original installation used #15 felt. This is a code upgrade item that belongs in the estimate.
Document the existing underlayment during tear-off. A photo showing #15 felt being removed supports the line item for its removal and the case for upgrading to a heavier product on the replacement.
Pricing in Xactimate
#15 felt is the least expensive underlayment option in Xactimate. If the estimate specifies #15 felt but the actual installation uses #30 felt or synthetic underlayment (as most modern installations do), the estimate understates the material cost. Verify that the line item matches what is actually being installed. The pricing difference between #15 felt, #30 felt, and synthetic underlayment is significant across a full roof and should be captured accurately.
Frequently asked questions
While #15 felt meets minimum building code requirements in many jurisdictions, most shingle manufacturers now recommend heavier #30 felt or synthetic underlayment for warranty coverage. Using #15 felt may void the shingle warranty.
#30 felt is thicker, heavier, and more durable than #15 felt. It provides better moisture protection, lies flatter, and is less likely to tear during installation. #30 felt costs more per square but is preferred by most manufacturers and inspectors.
No credit card required