Roofing Felt Tar Paper: A Comprehensive Guide to Underlayment for Achieving Durable Roofs

Roofing felt, commonly called tar paper, is a dependable underlayment that sits between the roof deck and the final shingles. This article explains what roofing felt is, the differences between tar paper and asphalt-saturated felt, how it functions in protection against moisture, and best practices for choosing and installing this essential component of a durable roof. Homeowners and contractors will gain practical guidance on assessing roof underlayment needs, selecting the right weight and type, and maintaining roof integrity through proper installation.

What Is Roofing Felt Tar Paper and Why It Matters

Roofing felt, or tar paper, is a fibrous sheet saturated with bitumen or asphalt to make it water-resistant. It acts as a secondary barrier against wind-driven rain and ice, protecting the roof deck when shingles are damaged or during installation. In colder climates, underlayment helps seal gaps that could allow moisture to penetrate the attic space. The term tar paper is traditional, but most modern products are asphalt-saturated felts designed for durability and ease of installation.

Types Of Roofing Felt And Their Characteristics

Underlayment materials vary in composition, thickness, and performance. The most common types are asphalt-saturated felt and synthetic underlayment, with tar paper often used as a historical term for the old or traditional felt. Asphalt-saturated felt comes in weights that indicate its thickness and strength, such as 15-pound, 30-pound, and 40-pound equivalents. Thin felts provide basic protection, while heavier felts deliver greater tear resistance and longer service in challenging weather. Synthetic underlayments, while not tar paper, are increasingly used for modern roofs due to higher durability and better tolerance to temperature changes.

Weights And What They Mean For Performance

Common categories include lighter 15- and 30-pound felts and heavier 40-pound equivalents. The weight generally reflects tear strength and durability rather than a strict quality measure. Heavier mats resist tearing when nails are driven or when the roof is walked during installation. In colder regions or steeper slopes, a heavier underlayment often provides better protection during extreme weather. When comparing products, consider tear resistance, puncture resistance, and compatibility with your chosen shingles.

Underlayment Function And Key Benefits

The primary role of roofing felt tar paper is to protect the roof deck from moisture intrusion during construction and weather events. It provides a secondary barrier if shingles are damaged, and it helps create a smooth surface for shingle installation. In many regions, it also offers temporary protection against wind-driven rain until roofing is completed. Additionally, a well-chosen underlayment can improve attic moisture control, reduce the risk of mold growth, and support consistent shingle adhesion by preventing deck irregularities from affecting the roof line.

Installation Guidelines For Roofing Felt

Proper installation is essential for maximum effectiveness. Start with clean, dry decking free of protrusions. Roll out the felt with an overlap that follows local building codes and manufacturer recommendations, typically 19 to 24 inches depending on the product and climate, or as specified for certain regions. Nails or staples should be driven with corrosion-resistant fasteners at consistent intervals, avoiding over-penetration that could tear the material. Always seal edges and joints with compatible sealant or flashing where appropriate to minimize moisture entry at seams.

Overlap, Sealing, And Fastening Best Practices

Overlaps are critical to water shedding. Long-edge overlaps should be oriented to prevent wind from lifting the sheets. Corner overlaps and along rakes require secure fastening and sometimes tape or sealant to seal seams. For exposed edges, apply edge fasteners per manufacturer instructions and ensure a continuous seal along all edges. In areas with heavy rainfall or snow, a more stringent overlap and sealing strategy reduces the risk of moisture penetration. Always follow the specific underlayment product guide for fastener type and spacing.

When To Use Tar Paper Versus Modern Synthetic Underlayment

Tar paper remains a dependable option for traditional roofs, restoration projects, or regions with lower moisture exposure. Synthetic underlayment often performs better in extreme weather, offers superior slip resistance, and provides longer service life. In many new constructions, builders opt for synthetic or composite underlayments to maximize durability and ease of installation. Homeowners should weigh cost, climate, roof pitch, and the anticipated lifespan of the roofing system when choosing between tar paper and modern alternatives.

Choosing The Right Roofing Felt For Your Roof

Key selection factors include climate, roof pitch, decking condition, and shingle type. In addition to weight, consider tear resistance, permeability, and compatibility with flashing and sealants. If a roof experiences frequent wind-driven rain or ice dam scenarios, a heavier or synthetic underlayment may provide better performance. Always verify product certifications, installation guidelines, and warranty terms to ensure alignment with local building codes and roof design goals.

Maintenance, Inspection, And Longevity

Roof underlayment does not require routine replacement like shingles, but inspections after severe weather will help identify damage early. Look for tears, holes, or lifted edges in the felt during attic or roof inspections. If damage is found, repairs should be scheduled promptly to maintain deck protection. While roofing felt typically lasts through the roof’s life, exposure, UV damage, or improper installation can shorten its effectiveness. Replacing underlayment is common during major roof renovations or when completing a full roof replacement.

Environmental And Safety Considerations

Tar paper and asphalt-saturated felts can contribute to waste streams at end of life. Some products contain recycled content or lower emissions in production, and many manufacturers offer recycling programs. When working on a roof, fall protection and proper PPE are essential. Use ladders, harnesses, and non-slip footwear, and follow all safety guidelines to prevent injuries during installation and inspection.

Common Mistakes To Avoid

Avoid skipping overlaps, using mismatched fasteners, and fanfolding the material in windy conditions. Do not install underlayment over dirty or wet decking, as moisture can trap beneath it. Postpone installation during rain or snow to prevent moisture entrapment and adhesion issues. Finally, never mix underlayment types on a single roof without verifying compatibility with flashing and shingles, as this can create weak points in the moisture barrier.

Cost And Availability

Roofing felt tar paper is widely available at home improvement centers and through roofing suppliers. Prices vary by weight, brand, and region. Heavier felts and synthetic underlayments typically cost more but may offer longer service life and fewer installation problems. When budgeting, include potential labor savings from easier installation with compatible underlayment and the anticipated lifespan of the roof system.