Roofing Felt: Traditional Roof Underlayment (2026)
Roofing felt, commonly called tar paper, is an asphalt-saturated organic or fiberglass mat used as roof underlayment. Available in #15 and #30 weights, it provides a water-resistant barrier between the roof deck and shingles. While being replaced by synthetics in many applications, felt remains a code-approved and economical option.
Key Features
- #15 and #30 weight options; Asphalt-saturated for water resistance; Traditional proven material; Code-approved underlayment; Economical choice
Specifications
Applications
- Under asphalt shingles; Under wood shakes; General roof underlayment; Temporary weather protection; Budget-conscious projects
Installation Overview
Roll horizontally from eave up. Overlap horizontal laps minimum 2 inches, end laps 4 inches. Fasten with plastic cap nails every 12 inches along edges and laps. Install ice barrier first at eaves in cold climates.
Pros & Cons
Pros
- ✓ Very affordable; Proven track record; Code-approved; Easy to install; Widely available at all suppliers
Cons
- ✗ Tears easily in wind; Wrinkles when wet; Heavier than synthetic; Short UV exposure limit; Can rot if trapped moisture
Top Brands
Code Requirements
Must meet ASTM D226 Type I (#15) or Type II (#30), or ASTM D4869. Required per IRC R905.2.7. #30 required for slopes below 4:12.
Buying Tips
If choosing felt over synthetic, use #30 for better durability. Plan to cover felt with roofing quickly - it degrades fast when exposed. Store rolls standing up and keep dry.
Frequently Asked Questions
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