Tar Paper for Roofing: A Comprehensive Guide to Roofing Felt

Tar paper, also known as roofing felt, has long been a foundational layer in many roof assemblies. This article explains what tar paper is, the different types and grades, how it functions in protection against moisture, and best practices for installation and maintenance. It also covers when to replace it and what modern alternatives may be suitable for today’s roofing projects. Understanding tar paper helps homeowners and professionals choose the right underlayment to extend roof life and improve overall performance.

What Tar Paper Is

Tar paper is a sheet-like membrane made from asphalt-impregnated felt. Traditionally, it comes in rolls and serves as an underlayment between the roof deck and the final roofing material. Its primary roles are to provide a secondary moisture barrier, improve wind resistance at the edges, and offer a smooth surface for shingles or tiles to seal against. Tar paper helps reduce water intrusion from small leaks or wind-driven rain and can contribute to overall roof longevity when properly installed.

Types And Grades Of Tar Paper

Tar paper is available in several formulations, each with specific benefits and limitations. The most common categories include:

• Standard Roofing Felt (No. 15 or No. 30): A traditional, asphalt-saturated cellulose or fiberglass felt. No. 15 is lighter and used for certain applications, while No. 30 offers greater strength and tear resistance.
• Ice and Water Shield: A high-quality underlayment with enhanced self-sealing properties around nails and fasteners, designed to provide superior moisture protection at eaves and in vulnerable roof zones.
• Fleece-Backed Or Self-Adhering: A self-adhesive membrane with a release paper, designed for easier installation and improved wind uplift resistance.
• Fiber-Glass vs. Asphalt-Saturated Felt: Fiberglass-based felt generally offers better tear resistance and longevity than traditional cellulose-based products.

When choosing tar paper, consider climate, roof pitch, and the type of final roofing material. In regions with heavy rainfall or snow, heavier underlayment and self-adhering options are commonly recommended.

How Tar Paper Works In A Roof Assembly

Tar paper sits between the roof deck and the final roofing material (shingles, tiles, or metal). It acts as a secondary line of defense against moisture that may penetrate the outer layer. In pitched roofs, it also helps shed water quickly and provides a wind-resistant surface for the top layer to seal against. The underlayment can add thermal protection and help smooth irregularities in the deck, contributing to a tighter, more durable roof assembly. Proper installation ensures laps shed water toward the eaves and that fasteners do not create leakage paths.

Installation Best Practices

Following manufacturer guidelines and local building codes is essential for tar paper installation. General best practices include:

• Deck Preparation: Ensure the roof deck is clean, dry, and free of debris. Repair any damaged areas before applying underlayment.
• Underlayment Positioning: Start at the eaves, with a slight downward slope toward the gutter. Overlap each subsequent course according to product specifications, typically 19 to 24 inches for felt and 2 to 4 inches for self-adhering membranes.
• Fastening And Sealing: Use appropriate nails or staples as recommended. For self-adhering products, remove the release sheet gradually to maintain proper adhesion and avoid air pockets.
• Edge Treatment: Secure edges and penetrations (chimneys, vents, and skylights) with proper taping or flashing to prevent wind uplift and moisture intrusion.
• Compatibility With Final Roof: Verify that the tar paper choice is compatible with the selected roofing material and any moisture barriers required by code.

Professional installation reduces the risk of wrinkles, air pockets, and premature failure. Contractors often install tar paper using a combination of nails and compatible sealants for a durable seal along eaves and valleys.

Common Issues And How To Troubleshoot

Even well-installed tar paper can encounter problems. Typical issues include:

• Punctures Or Tears: Sharp edges, nails, or foot traffic can damage underlayment. Small repair patches or re-installation may be necessary, depending on extent.
• Wrinkles Or Buckling: Occurs when the underlayment is not properly secured or when decking expands and contracts with temperature. Re-securing and re-lapping may be required.
• Water Stains After Rain: Often indicates gaps in laps, improper flashing, or improper slope. Inspect edges, penetrations, and flashing details for leaks.
• Incompatibility With Final Material: Some roofing products require specific underlayments. Ensure compatibility to prevent premature failure.

Maintenance And Replacement Considerations

Tar paper is not a permanent roof component. In many cases, underlayment life spans range from 15 to 30 years, influenced by climate, exposure, and roof design. Routine inspections after heavy weather help identify wear or damage early. Replacement is typically recommended during roof renovations or when persistent issues arise. If a roof system is being replaced with modern synthetic underlayment, obsolescence of traditional tar paper is common in high-performance builds.

Alternatives And Modern Practices

Advancements in underlayment technology have expanded options beyond traditional tar paper. Notable alternatives include:

• Synthetic Roofing Felt: Made from polyethylene or polypropylene fibers, offering greater tear resistance, lighter weight, and longer life than conventional felt.
• Self-Adhering Underlayment: A peel-and-stick membrane with a high-triction surface for wind resistance and reliable sealing around fasteners.
• Rubberized Asphalt And Peel-And-Stick Membranes: High-performance options designed for low-slope roofs and challenging climates.
• Ice And Water Shields: Specialized membranes applied at eaves and valleys to guard against ice dams and water intrusion in freezing conditions.

For many modern installations, synthetic and self-adhering underlayments provide enhanced durability and installation efficiency, while preserving moisture protection. In traditional or historic renovations, tar paper may still be appropriate where codes permit and contractors prefer its familiarity and cost-effectiveness.

Practical Tips For Selecting Tar Paper

• Climate Considerations: Choose heavier weights and self-adhering varieties in areas with snow, ice, and heavy rain.
• Roof Type And Slope: Low-slope roofs often require more robust underlayment systems to prevent water ingress.
• Code Requirements: Verify local building codes for underlayment specifications and required fire ratings.
• Compatibility: Ensure the underlayment is compatible with shingles, tiles, or metal roofing products for best results.

Table: Tar Paper vs. Modern Underlayment