What Is Roof Felt Used For

What Is Roof Felt Used For: Essential Functions and Benefits

Roof felt, also known as roofing felt paper or tar paper, is a crucial material in residential and commercial roofing systems. It serves as an underlayment beneath shingles or other roofing materials, providing a protective barrier. This article explores the diverse uses of roof felt, its composition, and why it remains an important component in effective roof construction.

Composition and Varieties of Roof Felt

Roof felt is typically made of either an organic or fiberglass mat saturated with asphalt or bitumen for waterproofing. Organic felts are made from wood cellulose fibers, while fiberglass felts use glass fibers for added durability. The felt is coated with asphalt to make it water-resistant, making it effective at preventing water penetration beneath the roofing material.

Roof felt comes primarily in two standard weights: 15-pound and 30-pound varieties, denoting the thickness and protection level provided. The 30-pound felt offers a thicker, more durable layer but is heavier to handle during installation. Both types are widely used depending on regional weather conditions and roofing requirements.

Primary Uses of Roof Felt in Roofing Construction

The main function of roof felt is to act as an underlayment beneath shingles or other roofing materials. It provides an important secondary barrier against water infiltration, protecting the roof deck from moisture damage during heavy rain or snow. Some specific uses include:

• Waterproof Barrier: Roof felt enhances waterproofing by preventing rainwater from reaching the roof decking in case shingles fail or shift.
• Protection During Installation: Roof felt safeguards the bare roof deck from weather exposure during shingles installation or roofing repairs.
• Improved Fire Resistance: Asphalt-saturated felt contributes to fire resistance, providing a layer that can slow the spread of flames.
• Improved Roof Longevity: By repelling moisture and protecting wood decking, roof felt helps extend the lifespan of roofing materials and structure.
• Ice and Water Barrier: In colder climates, roof felt can be combined with peel-and-stick membranes to resist ice dam formation and water backup.

How Roof Felt Enhances Roof Durability and Performance

Roof felt enhances overall roof system durability by acting as a protective cushion between the roof deck and the outer roofing materials. It reduces wear and tear caused by thermal expansion, contraction, and shifting of shingles. Additionally, it reduces the risk of leaks caused by wind-driven rain.

By creating a smooth, uniform surface for the installation of shingles or tiles, roof felt reduces uneven pressure points that may otherwise damage roofing materials over time.

Comparing Roof Felt to Modern Synthetic Underlayments

While roof felt has been a traditional underlayment for decades, synthetic roofing underlayments have grown in popularity. Synthetic options are made from polypropylene or polyester materials and offer improved tear resistance, lighter weight, and increased UV durability.

However, roof felt remains widely used due to its cost-effectiveness and proven waterproofing capabilities. It is particularly favored in residential projects, historic restorations, and areas where traditional roofing practices prevail.

Proper Installation of Roof Felt: Key Considerations

Effective installation of roof felt is essential for maximizing its benefits. Recommended practices include:

• Starting at the eaves: Lay the felt horizontally, overlapping each row by 2 to 4 inches to ensure complete waterproof coverage.
• Securing the Felt: Use roofing nails or staples to fasten the felt securely to the roof deck without tearing it.
• Maintaining Alignment: Keep the felt flat and wrinkle-free to prevent water pooling and improve shingle adhesion.
• Weather Considerations: Avoid exposed installation to direct sunlight longer than recommended, as prolonged exposure can degrade the asphalt coating.

Common Misconceptions About Roof Felt

Several myths about roof felt can mislead homeowners or contractors. For instance:

• Myth: Roof felt alone waterproofs the entire roof.
  Fact: Roof felt acts as a secondary barrier; proper installation of shingles or other roofing materials is necessary for full waterproof protection.
• Myth: Thicker felt always means a better roof.
  Fact: The appropriate felt weight depends on climate, roofing materials, and local code requirements.
• Myth: Synthetic underlayments always outperform roof felt.
  Fact: Both materials have pros and cons; roof felt remains a reliable and cost-effective choice in many scenarios.

Environmental and Safety Aspects of Roof Felt

Roof felt’s asphalt content means it is somewhat petroleum-based, which raises environmental concerns. However, advances in manufacturing have led to options with reduced emissions and recycled content. Proper disposal or recycling of used roofing felt is recommended to minimize landfill impact.

Safety during installation includes using gloves and masks to avoid dermatological or respiratory irritation from asphalt fumes.

Summary