#30 Felt Paper

The Heavier Traditional Option

#30 felt paper is a heavier grade of asphalt-saturated roofing underlayment at approximately 30 pounds per 100 square feet, offering significantly more durability and moisture protection than #15 felt. Before synthetic underlayment became widely available, #30 felt was the professional standard for quality residential roofing installations. It is thicker, resists tearing better during installation, and provides a more reliable moisture barrier than its lighter counterpart.

Understanding the differences between underlayment types ensures the insurance estimate uses the correct line item and pricing.

#30 Felt in Current Practice

While synthetic underlayment has become the dominant product in most markets, #30 felt remains in use and is still an acceptable underlayment for many shingle manufacturers. On insurance claims, the choice between #30 felt and synthetic underlayment depends on what the manufacturer requires for warranty coverage and what the local building code specifies. If the manufacturer's installation instructions allow either product, the estimate should reflect whichever one the contractor is actually installing.

In practice, many contractors have switched entirely to synthetic because it performs better in the field and simplifies material ordering.

Getting the Line Item Right

#30 felt has a different Xactimate line item and unit price than #15 felt and synthetic underlayment. The cost falls between the two: more expensive than #15 felt, less expensive than most synthetic products. On a full roof replacement, the underlayment covers the entire deck, so using the correct line item matters. If the estimate shows #15 felt but the contractor installs #30 felt, the contractor is absorbing the price difference. Accurate line item selection at the estimating stage prevents this gap.