Roofing felt, commonly known as tar paper, is a traditional underlayment material used beneath shingles to provide protection against moisture and wind. While newer synthetic underlayments are gaining popularity, felt remains a cost-effective, widely available option in many regions. This article covers what roofing felt is, its types, installation guidelines, durability considerations, maintenance tips, and how it compares with modern alternatives. Understanding how tar paper works helps homeowners and builders make informed decisions about roof protection and long-term performance.
What Is Roofing Felt And How Does It Work
Roofing felt is an asphalt-impregnated felt paper designed to act as a secondary barrier between the roof deck and shingles. It helps seal against minor water intrusion, provides temporary protection during installation, and improves wind uplift resistance when used correctly. Traditional felt is produced from organic fibers such as cellulose or organic mats coated with asphalt. The result is a breathable, water-resistant layer that slows moisture penetration while allowing moisture vapor to escape from the attic space.
Types Of Roofing Felt
Roofing felt comes in several varieties, each with distinct performance characteristics. Organic asphalt-saturated felt uses cellulose or jute as a base and is coated with asphalt. It is economical and effective in many climates but can deteriorate rapidly when exposed to prolonged UV light. Synthetic roofing felt employs fiberglass or polypropylene bases with asphalt or polymer-modified coatings for enhanced durability and tear resistance. Urethane- or bitumen-modified felts offer improved flexibility and weather resistance in variable temperatures. The choice depends on climate, roof slope, and project timeline.
Installation Guidelines For Tar Paper
Proper installation ensures maximum performance and reduces the risk of leaks. Begin with clean, dry decking and a suitable starter course. Use asphalt-saturated felt in rolls at standard widths, typically 3 feet by 144 feet, and unroll parallel to the gutters. Overlay edges by about 2 to 4 inches and seal seams with compatible roofing cement or fasteners as recommended by the manufacturer. In cold weather, allow the felt to relax and avoid tearing; in hot weather, handle gently to prevent softening. Use corrosion-resistant nails or staples, and avoid over-stretching the material, which can cause wrinkles and gaps.
- Start at the bottom edge and work upward, overlapping the previous course by a minimum of 2 inches.
- Install before applying drip edge and shingles to maintain a continuous moisture barrier.
- Ensure proper venting and attic pressure balance to minimize moisture buildup behind the underlayment.
Most modern shingles and underlayment systems specify a specific felt type and installation method. Always consult the manufacturer’s instructions for acceptable underlayment overlaps, nailing patterns, and weather exposure limits. For steep-slope roofs, ensure the nails are driven straight and fully seated to prevent tearing during wind uplift.
Durability, Performance And Common Issues
Durability varies by type and exposure. Organic felt is susceptible to deterioration from UV exposure, temperature fluctuations, and moisture, especially in humid climates. Synthetic felts generally offer greater resistance to tearing, faster rain resistance, and longer service life, but can be more expensive. Common issues include wrinkling from improper installation, gaps at joints, blistering when moisture becomes trapped, and accelerated wear if the roof experiences prolonged sunshine or freezing-thaw cycles. Regular inspection after severe weather can help identify compromised sections before leaks form.
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Maintenance And Replacement Considerations
Maintenance focuses on inspecting underlayment condition during roof lifespans. Look for exposed tar paper during shingle removal or re-roof projects, which indicates improper coverage or wind uplift damage. If felt is visibly damaged, torn, or has multiple areas of exposed decking, replacement is advisable to maintain a continuous moisture barrier. In older homes, consider upgrading to synthetic underlayment for improved durability and easier installation. Seasonal maintenance includes clearing debris from gutters and ensuring proper attic ventilation to reduce moisture buildup behind the roof covering.
Roofing Codes, Weather, And Regional Practices
Codes and best practices for roofing underlayment vary by state and municipality. In many U.S. regions, felt is permitted or required as a secondary moisture barrier in addition to the primary roof covering. Coastal areas with high wind exposure may require specific nailing patterns and overlaps to resist wind forces. In regions with heavy precipitation or freeze-thaw cycles, synthetic underlayments often perform better due to higher tear resistance and lower moisture absorption. Homeowners should verify local requirements and consult a licensed roofer to determine the most appropriate underlayment strategy for the climate and structure.
Tar Paper Versus Synthetic Underlayment: Pros And Cons
Both options have advantages. Tar paper is cost-effective, readily available, and easy to install for many traditional roofs. It provides a reliable moisture barrier when installed correctly but has shorter life expectancy in sun-drenched or humid climates. Synthetic underlayment offers higher tear strength, lighter weight, better performance in extreme temperatures, and longer service life, but at a higher upfront cost. For new construction or major renovations in challenging climates, synthetic materials often provide superior long-term value, especially when combined with modern shingles and proper attic ventilation.
Practical Tips For Homeowners
When selecting roof underlayment, consider climate, roof slope, and expected exposure. If choosing tar paper or felt, opt for high-quality, asphalt-saturated products from reputable brands, and follow installation guidelines precisely. Maintain proper attic ventilation to reduce moisture behind the underlayment. Schedule inspections after severe storms to identify loose edges, blistering, or water staining on interior ceilings, and address issues promptly to prevent costly repairs.
Frequently Asked Questions
- What is tar paper used for in roofing? It serves as a protective moisture barrier beneath shingles, delaying water intrusion and aiding temporary weatherproofing during installation.
- How long does roofing felt last? Organic felt may last 5–15 years depending on climate and UV exposure; synthetic felts typically last longer, often 15–25 years or more with proper care.
- Can I install roofing felt myself? Yes, with proper safety, tools, and adherence to manufacturer guidelines. Professional installation is recommended for complex structures and high-wind areas.