Roofing Felt vs Tar Paper are common underlayment options for shingle roofs, often used interchangeably though they differ in composition, performance, and installation considerations. This article explains the distinctions, pros and cons, typical applications, and guidance to help homeowners, contractors, and specifiers choose the right product for a given project.
| Feature | Roofing Felt | Tar Paper |
|---|---|---|
| Material | Asphalt-saturated felt; available in organic and fiberglass faces | Asphalt-impregnated paper; usually lighter and cheaper |
| Durability | Higher with fiberglass or heavier weights (30/40/60/90) | Lower tear resistance; prone to moisture damage over time |
| Water Resistance | Good under shingles; some are self-sealing | Moderate; often used on older or secondary roofs |
| Breathability | Varies; some allow vapor escape | Less vapor control; can trap moisture in certain assemblies |
| Cost | Moderate to higher | Lower initial cost |
What Roofing Felt And Tar Paper Are
Roofing felt is a manufactured underlayment made by saturating a base sheet—either organic cellulose or fiberglass—with asphalt or bitumen to create a water-resistant membrane under shingles. The industry commonly refers to felt by its weight categories (15-pound, 30-pound, etc.), though modern felt uses grams per square meter or designations like 15#/30# for historical reference.
Tar paper historically describes a paper base impregnated with coal tar or asphalt. It is typically thinner and less robust than heavier asphalt-felt products. Tar paper often refers to traditional builds and is still used in some regions for temporary protection or certain low-cost roofing applications.
Material Composition And Manufacturing Differences
Organic Felt vs Fiberglass-Faced Felt—Organic felts use cellulose or recycled rags as the base, which absorb asphalt readily, giving good adhesion and pliability but making them vulnerable to rot if soaked. Fiberglass-faced felts use a non-woven fiberglass mat that resists tearing, is lighter, and provides more dimensional stability under heat and UV exposure.
Tar Paper Composition—Tar paper generally uses a paper or cellulose base with a tar or asphalt coating. The coating may be lighter, providing basic water resistance but less structural integrity. Some modern “tar papers” are asphalt-impregnated cellulose that mimic traditional products but with varying quality.
Performance: Water Resistance, Durability, And Longevity
Water Resistance—Both roofing felt and tar paper act as secondary water barriers beneath shingles. Heavier felts (30-pound or 40-weight equivalents) resist water penetration better than lightweight tar papers. However, neither replaces a waterproof membrane in roof assemblies prone to ice dams or ponding water.
Durability And Tear Resistance—Fiberglass-faced roofing felt typically offers the best tear resistance and long-term durability. Organic felts are durable when kept dry but can deteriorate if exposed for long periods. Tar paper has the lowest tear resistance and can ravel or delaminate when wet or subjected to foot traffic.
Longevity—When properly installed and covered by shingles promptly, quality roofing felt can last the life of the roof underlaying materials. Tar paper may degrade faster, especially in humid climates or where installation delays expose it to sunlight and moisture.
Installation Considerations And Best Practices
Underlayment Selection—Choose roofing felt based on local code, climate, and roof complexity. For steep-slope asphalt shingle roofs, 30-weight (or 30# equivalent) felt is often specified for better protection and handling. Use fiberglass-faced felts for wind-prone or high-heat environments where dimensional stability is important.
Fastening And Overlaps—Install underlayment with appropriate overlaps (commonly 2–4 inches side lap and 4–6 inches end lap) and fasten according to manufacturer recommendations—typically with roofing nails or staples at specified spacing. Improper fastening can allow wind uplift or water intrusion.
Exposure Time—Limit exposure of felt or tar paper to sunlight and weather. Extended exposure can cause asphalt oxidation, embrittlement, and loss of adhesion. If the roof deck is likely to remain open for several days, use a synthetic underlayment engineered for long exposure.
Code, Standards, And Modern Alternatives
Building Codes—Local building codes often reference underlayment requirements for fire classification, ice barrier zones, and wind resistance. Many codes accept standard asphalt-saturated felt but increasingly allow or prefer synthetic underlayments for improved performance.
Synthetic Underlayments—Modern synthetic underlayments made of polypropylene or polyethylene blends offer superior tear resistance, lighter weight, hydrophobic properties, and extended UV exposure tolerance. While more expensive, they reduce installation damage and can improve roof longevity in harsh climates.
Cost Comparison And Value Assessment
Initial Cost—Tar paper typically has the lowest upfront cost, with traditional felt at moderate cost and synthetic underlayment costing more. Material differences may represent a small fraction of total roofing costs, where labor and shingles dominate.
Value Over Time—Higher-quality felt or synthetic underlayment often delivers better value by reducing rework, resisting installation damage, and improving roof system performance. For homeowners intending to stay in a property long-term, investing slightly more in durable underlayment can reduce repair risk and insurance claims against roof leaks.
Where Roofing Felt Or Tar Paper Are Best Used
Typical Applications for Roofing Felt—Roofing felt is commonly used under asphalt shingles on residential homes. It is appropriate for most temperate climates and is compatible with most roofing accessories and flashing details. Use heavier felt for exposed ridgelines, valleys, or where foot traffic during installation is expected.
When Tar Paper Is Used—Tar paper is often used as a temporary weather barrier during construction or for low-budget repairs. It may be found in older homes or in specific historic restoration projects seeking authenticity. It is less appropriate for high-performance roofing needs or extended exposure.
Environmental And Safety Considerations
Environmental Impact—Traditional asphalt-saturated felts and tar paper are petroleum-derived and not typically recyclable. Newer synthetic underlayments may use polymers that similarly pose end-of-life considerations. Choosing suppliers with sustainable manufacturing practices and disposal plans can mitigate environmental impact.
Fire And Health—Some underlayments carry fire ratings important in wildfire-prone areas. Installers should follow safety protocols to avoid inhalation of dust during cutting and wear gloves to protect from asphalt and bitumen contact. Always check product safety data sheets for handling guidance.
Common Myths And Misconceptions
“Tar Paper And Felt Are The Same”—While often used interchangeably in casual conversation, tar paper is not identical to modern asphalt roofing felt; felt offers a broader range of compositions and performance levels. Mislabeling can lead to inappropriate product choice.
“Heavier Means Better”—Weight is one indicator of durability, but material technology matters. A lightweight fiberglass-faced felt may outperform an old-style heavier organic felt in tear resistance and weather tolerance.
Practical Tips For Homeowners And Contractors
- Confirm Local Code Requirements before selecting underlayment, especially in ice dam or wildfire zones.
- Match Underlayment To Shingle Type—Certain architectural shingles specify underlayment compatibility for warranties.
- Minimize Exposure—Schedule shingle installation soon after underlayment to prevent UV and moisture damage.
- Inspect Decking—Install underlayment only on dry, sound decking to prevent trapped moisture and rot.
- Consider Synthetic Options for long exposure windows, severe climates, or lightweight handling needs.
How To Decide Between Roofing Felt And Tar Paper
Assess Project Priorities—If cost is the primary constraint and exposure time will be minimal, tar paper or a basic felt may be acceptable. For durability, wind and UV resistance, and fewer installation risks, choose a quality asphalt-saturated felt or a synthetic underlayment.
Get Professional Input—A qualified roofer or building inspector can evaluate roof pitch, local climate, roofing material, and code requirements to recommend an appropriate underlayment. Document the choice to support warranty claims and resale disclosures.
Key Takeaways For Roofing Felt Vs Tar Paper
Roofing felt and tar paper serve the same basic purpose as underlayment, but they differ significantly in composition, durability, and performance. Roofing felt—especially fiberglass-faced or higher-weight varieties—generally offers superior tear resistance, weather tolerance, and longevity. Tar paper is lower cost and suitable for temporary protection or specific low-performance uses. Modern synthetic underlayments provide an alternative when extended exposure, lightweight handling, or enhanced performance is required.
Choosing the right underlayment involves balancing cost, climate, installation timing, and expected roof life, and professional guidance ensures compliance and optimal performance.