Roofing Felt vs Tar Paper: A Practical Guide for Homeowners

The terms roofing felt and tar paper are often used interchangeably, but they refer to specific materials with distinct compositions, performance characteristics, and best-use scenarios. This article explains what each material is, how they differ, and which option fits particular climates, roof designs, and maintenance plans. Understanding these differences helps homeowners make informed choices for underlayment, protect against moisture, and extend roof life.

Background And Definitions

Roofing felt, also known as asphalt-saturated felt, is traditionally made by saturating a felt base with asphalt. It comes in various weights, commonly 15-pound and 30-pound, indicating the thickness and strength of the material. Tar paper is an older term that often refers to the same asphalt-saturated products or to earlier versions before modern basematerials evolved. Modern materials may be fiberglass- or organic-based and use polymer-modified asphalt or elastomeric coatings to improve performance.

Roofing Felt And Tar Paper: Core Differences

• Composition: Traditional roofing felt uses a paper or fiberglass base with asphalt saturant. Tar paper historically described similar products and can vary by base material and asphalt type.
• Weight And Strength: 15-pound felt is lighter and more flexible; 30-pound felt provides greater tear resistance and is common for harsher conditions or steeper slopes.
• Base Material: Modern options include organic felts and fiberglass felts. Fiberglass-based products resist tearing and are less prone to shrinkage.
• Moisture Protection: Both act as secondary moisture barriers when installed correctly under shingles, preventing wind-driven rain from infiltrating the roof deck during construction and temporary exposure.
• Durability Under UV: Roofing felt is designed for temporary UV exposure during installation; extended sun exposure should be avoided to prevent premature degradation.

Applications By Climate And Roof Type

Choosing between roofing felt and tar paper often depends on climate, roof design, and local building codes. In temperate climates with regular rain, a reliable underlayment is essential to minimize water intrusion during storms. For roofs with high-wind areas or complex flashings, a heavier felt (such as 30-pound) can provide greater protection. In some regions, building codes specify underlayment requirements that favor specific products or weight classes. Modern installations may also use self-adhering membranes or synthetic underlayments as alternatives to traditional felt.

Installation Tips And Best Practices

• Proper Coverage: Overlap edges by 2 to 4 inches and maintain shingle alignment to ensure continuous protection.
• Weather Window: Install underlayment only when temperatures are above freezing and the roof deck is dry to prevent premature bonding or wrinkles.
• Nail Pattern: If using traditional felt, fasten per manufacturer guidelines to avoid revealing the deck to wind uplift.
• Self-Adhering Alternatives: In wet climates or on difficult roofs, self-adhesive underlay membranes can reduce water intrusion during installation.
• Ventilation And Drainage: Ensure soffit and ridge ventilation remain unobstructed to prevent moisture buildup behind the underlayment.

Durability, Lifespan, And Maintenance

Underlayment is a temporary skin protecting the roof deck during construction and through the first cycles of weather. The expected lifespan of a traditional felt underlayment is influenced by climate, sun exposure, and roof slope. Heavier weights generally offer greater resistance to wind and tearing but do not replace the need for timely roof replacement. Regular inspections after severe weather help identify punctures, wrinkles, or lifting that could compromise protection. When damaged, underlayment sections should be repaired or replaced by a qualified contractor to maintain a continuous barrier.

Alternatives And Modern Options

• Synthetic Underlayment: Often made from polypropylene or polyethylene, synthetic underlayments are lighter, more durable, and provide excellent water resistance. They resist tearing and are less sensitive to UV exposure.
• Self-Adhering Underlayment: A peel-and-stick membrane that bonds to the deck, offering superior seal against moisture and better performance in cold or windy conditions.
• Rubberized Asphalt: A more flexible option that can conform to irregular roof surfaces, providing a robust moisture barrier.
• Transition To Roofing Materials: When paired with modern shingles, the combination of synthetic underlayment and correct flashing enhances long-term protection against leaks.

Frequently Asked Questions

Which is better, roofing felt or tar paper? In modern practice, synthetic or self-adhering underlayments are often preferred for durability and ease of installation. Traditional asphalt-saturated felt remains common in certain regions or older homes but may require more maintenance over time.

Does climate affect the choice? Yes. Wet, windy, or cold climates may benefit from heavier felt or advanced synthetic underlayments to withstand weather exposure and wind uplift. Dry regions with mild conditions may tolerably use standard felt where permitted by code.

Can I install underlayment directly under shingles? Yes, underlayment is installed as a moisture barrier beneath shingles. Proper installation, flashing, and ventilation are essential for effective protection.

How long does underlayment last? Underlayment is designed to protect during construction and early roof life. Its durability depends on material type, weather exposure, and roof design. Regular inspection helps identify wear before failures occur.