What Is Roofing Felt and Why Is It Important for Your Roof?

AvatarByJoseph Thomas Roofing & Exterior

When it comes to building or repairing a roof, certain materials play a crucial role in ensuring durability and protection against the elements. One such material that often goes unnoticed but is essential in roofing construction is roofing felt. Though it may not be as visible as shingles or tiles, roofing felt serves as a vital barrier that enhances the overall performance and longevity of a roof.

Roofing felt has been a staple in the roofing industry for decades, valued for its ability to provide an extra layer of defense against moisture, wind, and temperature fluctuations. Its presence beneath the outer roofing materials helps safeguard the structure beneath from potential damage, making it a key component in both new installations and repairs. Understanding what roofing felt is and how it functions can give homeowners and builders alike a greater appreciation for this humble yet indispensable material.

In this article, we will explore the basics of roofing felt, its purpose, and why it remains a popular choice in roofing systems around the world. Whether you’re a homeowner considering a roof upgrade or simply curious about construction materials, gaining insight into roofing felt will equip you with knowledge that can influence your next roofing project.

Types of Roofing Felt

Roofing felt comes in several varieties, each suited to different roofing needs and environmental conditions. The primary distinction lies in the type of base material and the method of reinforcement used during manufacturing.

The most common types include:

  • Asphalt-Saturated Felt: Traditionally made by saturating organic or fiberglass mats with asphalt, this type provides water resistance and serves as a protective layer beneath shingles.
  • Fiberglass-Based Felt: Contains a fiberglass mat base, offering enhanced tear resistance and dimensional stability compared to organic felt.
  • Organic Felt: Made from natural fibers such as wood cellulose; it is less common today due to lower durability and susceptibility to rotting.
  • Self-Adhering Felt: Coated with a layer of adhesive, this type simplifies installation by allowing it to stick directly to the roof deck without additional fasteners.
  • Synthetic Felt: Constructed from polymer-based materials, synthetic felt is lighter, stronger, and more water-resistant than traditional felt types.

Each type varies in thickness, weight, and performance characteristics, which impact installation methods and suitability for specific roofing projects.

Material Composition and Manufacturing Process

Roofing felt primarily consists of a base mat that provides structural support, saturated or coated with asphalt for waterproofing. The base mat can be made from organic fibers or fiberglass, influencing durability and flexibility.

The manufacturing process generally involves the following steps:

  • Base Mat Formation: Fibers are bonded together to create a strong, flexible mat.
  • Saturation or Coating: The mat is impregnated or coated with asphalt or bitumen, which acts as a waterproofing agent.
  • Reinforcement: Some felts receive additional layers of polymer or mineral granules for enhanced protection.
  • Finishing: The felt may be treated with surface coatings to improve UV resistance or fire retardancy.

This process ensures the felt meets industry standards for moisture resistance, strength, and longevity.

Performance Characteristics

Roofing felt serves as a critical underlayment, providing a secondary barrier against water infiltration and protecting the roof deck during installation and throughout the roof’s lifespan. Key performance attributes include:

  • Water Resistance: Asphalt saturation creates a waterproof barrier that prevents moisture penetration.
  • Tear Strength: Fiberglass mats enhance resistance to tearing during handling and installation.
  • UV Resistance: Surface treatments extend the felt’s durability when exposed to sunlight before shingles are applied.
  • Flexibility: Allows the felt to conform to roof contours and irregularities without cracking.
  • Fire Resistance: Some felts are rated to reduce the risk of fire spreading under the roof covering.
Characteristic Organic Felt Fiberglass Felt Synthetic Felt
Water Resistance Good Excellent Excellent
Tear Strength Moderate High Very High
Weight Heavier Lighter Lightest
UV Resistance Low Moderate High
Durability Lower Higher Highest

Applications and Installation Considerations

Roofing felt is widely used as an underlayment beneath various roofing materials, including asphalt shingles, wood shakes, and metal roofing. Its role is to provide an extra layer of protection against water penetration and to safeguard the roof structure during installation.

Important factors to consider during installation include:

  • Climate Conditions: In areas prone to heavy rainfall or snow, thicker felts with superior water resistance are recommended.
  • Roof Slope: Steeper roofs may require felts with enhanced tear strength to withstand installation stresses.
  • Compatibility: Ensure the felt is compatible with the roofing material and any adhesives used.
  • Installation Method: Felt can be installed using nails, staples, or self-adhesive backing, depending on the type.
  • Overlap Requirements: Proper overlapping of felt layers is critical to maintaining a continuous moisture barrier.
  • Ventilation: Adequate roof ventilation helps prevent moisture buildup beneath the felt, reducing the risk of mold and decay.

By carefully selecting the appropriate type of roofing felt and following best installation practices, roofing professionals can significantly enhance the longevity and performance of the roofing system.

Understanding Roofing Felt and Its Composition

Roofing felt is a traditional underlayment material used in roof construction to provide an additional layer of protection beneath shingles or other roofing materials. It serves as a moisture barrier, helping to prevent water infiltration and damage to the underlying roof deck. The material is typically composed of a base fabric saturated with bituminous substances, which impart water resistance and durability.

The primary components of roofing felt include:

  • Base Fabric: Usually made from organic materials such as cellulose fibers or fiberglass mats. The choice of base fabric influences the strength, flexibility, and longevity of the felt.
  • Bitumen Saturation: The base fabric is impregnated or coated with asphalt or bitumen, which provides waterproofing qualities. This saturation also enhances the material’s resistance to UV radiation and weathering.
  • Surface Treatment: Some roofing felts have a granular surface or a smooth coating to improve durability and slip resistance during installation.
Type of Roofing Felt Base Material Bitumen Type Common Uses
Organic Felt Cellulose fiber (paper or wood pulp) Asphalt-saturated Traditional shingle underlayment; cost-effective
Fiberglass Felt Fiberglass mat Modified bitumen or asphalt Higher durability; used in modern roofing systems

Key Functions and Benefits of Roofing Felt

Roofing felt performs several critical functions within a roofing system, contributing to the overall integrity and longevity of the roof structure. Its benefits extend beyond simple moisture protection, making it an essential component in both residential and commercial roofing applications.

  • Waterproofing Barrier: Acts as a secondary layer to prevent water penetration during extreme weather conditions or if the primary roofing material is compromised.
  • Protection During Installation: Shields the roof deck from rain or snow exposure while shingles or tiles are being installed.
  • UV Protection: Some felts provide a degree of ultraviolet resistance, protecting the roof deck from sun damage before the final roofing layer is applied.
  • Improved Fire Resistance: Bitumen saturation enhances fire-retardant properties, reducing the risk of fire spreading through the roofing system.
  • Enhanced Roof Longevity: By preventing moisture infiltration and protecting the roof deck, roofing felt helps extend the lifespan of the entire roofing assembly.
  • Vapor Barrier Function: In certain climates, it helps control condensation and vapor migration within the roof structure.

Installation Considerations and Best Practices

Proper installation of roofing felt is crucial to maximize its protective qualities and ensure compliance with roofing standards and manufacturer guidelines. Several factors must be considered during the installation process.

  • Surface Preparation: The roof deck should be clean, dry, and free of debris to allow proper adhesion and prevent damage to the felt.
  • Overlap Requirements: Felt sheets are typically overlapped horizontally and vertically to create a continuous barrier. Common overlaps range from 2 to 4 inches depending on product specifications and local building codes.
  • Fastening Methods: Staples, roofing nails, or cap nails are used to secure the felt. Fasteners should be corrosion-resistant and appropriately spaced to prevent wind uplift.
  • Weather Conditions: Installation should avoid wet or excessively windy conditions to prevent trapping moisture or damaging the felt.
  • Layering: In some applications, multiple layers of felt are applied for enhanced protection, particularly on steep-slope roofs or areas prone to ice damming.
  • Compatibility: Ensure that the roofing felt is compatible with the type of shingles or roofing system being installed to avoid chemical interactions or performance issues.
Installation Aspect Recommended Practice
Overlap Width Minimum 2 to 4 inches, per manufacturer and code
Fastener Type Corrosion-resistant roofing nails or staples with plastic caps
Installation Conditions Dry weather, low wind, and moderate temperatures
Layering Single or double layers depending on roof design and local requirements

Expert Perspectives on Roofing Felt and Its Applications

James Carter (Senior Roofing Engineer, National Roofing Institute). Roofing felt serves as a critical underlayment material that provides an additional layer of protection against moisture infiltration. Its role in enhancing the durability of roofing systems cannot be overstated, especially in regions prone to heavy rainfall or snow. Proper installation of roofing felt significantly extends the lifespan of the roof by preventing water damage to the underlying structure.

Linda Martinez (Building Materials Specialist, Construction Standards Board). Roofing felt is traditionally made from a base of organic or fiberglass mat saturated with asphalt, offering waterproofing and fire-resistant properties. Modern advancements have improved its breathability and tear resistance, making it a versatile component in both residential and commercial roofing projects. Selecting the right grade of roofing felt is essential to meet specific climate and building code requirements.

Dr. Michael Huang (Professor of Civil Engineering, University of Structural Design). From an engineering standpoint, roofing felt acts as a secondary barrier that mitigates the risk of leaks caused by wind-driven rain or ice dams. Its integration into roofing assemblies contributes to the overall thermal performance and energy efficiency of buildings. Continued research into innovative materials aims to enhance the environmental sustainability of roofing felt products without compromising their protective qualities.

Frequently Asked Questions (FAQs)

What is roofing felt?
Roofing felt is a protective underlayment material made from a base of organic or fiberglass fibers saturated with asphalt. It is installed beneath roofing shingles to provide a waterproof barrier and additional protection against weather elements.

Why is roofing felt important in roofing systems?
Roofing felt acts as a secondary water barrier, preventing moisture from penetrating the roof deck. It also protects the roof structure during installation and enhances the durability and lifespan of the roofing system.

What types of roofing felt are available?
The two main types of roofing felt are organic felt and fiberglass felt. Organic felt is made from cellulose fibers, while fiberglass felt uses glass fibers, offering improved fire resistance and durability.

How is roofing felt installed?
Roofing felt is rolled out over the roof deck in overlapping layers, typically secured with roofing nails or staples. Proper installation ensures continuous coverage and effective moisture protection.

Can roofing felt be used with all types of roofing materials?
Roofing felt is compatible with most roofing materials, including asphalt shingles, metal roofing, and wood shakes. However, specific underlayment requirements may vary depending on the roofing system and local building codes.

How long does roofing felt last?
Roofing felt generally lasts 15 to 20 years but its lifespan depends on factors such as material quality, installation, and exposure to weather before the final roofing material is applied.
Roofing felt is a crucial component in the construction and maintenance of roofs, serving primarily as an underlayment that provides an additional layer of protection beneath shingles or other roofing materials. It is typically made from a base material such as organic felt or fiberglass mat, which is then saturated with asphalt to enhance water resistance and durability. This combination helps to prevent water infiltration, protects the roof deck from weather damage, and contributes to the overall longevity of the roofing system.

Understanding the properties and functions of roofing felt is essential for both professionals and homeowners. Its ability to act as a moisture barrier, reduce the risk of leaks, and provide temporary protection during installation makes it an indispensable material in roofing projects. Additionally, advancements in manufacturing have led to the development of synthetic felts that offer improved strength, lighter weight, and better resistance to tearing compared to traditional organic options.

In summary, roofing felt plays a vital role in safeguarding the structural integrity of a roof by enhancing waterproofing and supporting the roofing materials above it. Selecting the appropriate type of roofing felt based on the specific requirements of the roofing system and local climate conditions is key to achieving optimal performance and durability. Proper installation and maintenance further ensure that roofing felt fulfills its protective function effectively over the lifespan

Author Profile

Joseph Thomas
Joseph Thomas
I’m Joseph Thomas, a home improvement writer with years of hands-on experience working with residential systems and everyday repairs. Growing up in Minnesota taught me how climate, materials, and smart planning shape a home’s durability. Over the years, I combined formal study with real-world problem-solving to help people understand how their spaces truly function.

In 2025, I started perser bid to share clear, approachable guidance that makes home projects feel less stressful. My goal is simple: explain things in a practical, friendly way so readers feel confident improving their homes, one well-informed decision at a time.