Is Felt Paper Necessary Under Shingles

The use of felt paper under shingles has long been a standard in roofing, but advances in materials and regional building codes have led many builders to consider alternatives. This article examines what felt paper is, its role in modern roofing, the pros and cons of using it, and when alternatives like synthetic underlayments or peel-and-stick membranes might be appropriate. It also covers installation considerations and how local requirements influence the decision.

What Is Felt Paper In Roofing

Felt paper, often referred to as roofing felt or tar paper, is a paper-based underlayment that is saturated with bitumen to create a moisture barrier. Traditionally available in 15-pound and 30-pound weights, felt paper provides an extra layer between the roof decking and the shingles. It helps catch small leaks and protects the deck during installation by offering a temporary weather-resistive barrier. While common in older homes, the material and construction have evolved, with synthetic underlayments becoming more prevalent in new builds.

Role Of Underlayment In Shingle Roofing

Underlayment serves three main purposes: secondary weather protection, protection for the decking during installation, and a surface for nailing shingles. Felt paper adds a layer that can slow down water intrusion if shingles are damaged, especially in areas prone to wind-driven rain. It also helps prevent fastener splits and paint bleed into the deck during early construction. In many climates, underlayment contributes to moisture management by providing a continuous barrier beneath the shingles during heavy rain or snowfall.

Pros And Cons Of Felt Paper

Pros

• Extra moisture barrier that can slow leaks when shingles fail or are damaged.
• Relatively low cost and easy to install with basic roofing tools.
• Provides a uniform surface for shingle installation and helps capture small drips during construction.

Cons

• Prone to wrinkling, bunching, or tearing, which can create voids and complicate installation.
• Absorbs water, potentially adding weight and increasing drying time after a wet period.
• Less durable in extreme UV exposure; synthetic and peel-and-stick options offer higher performance in some climates.
• Can harbor mold or mold spores if moisture becomes trapped, especially in poorly ventilated attics or crawlspaces.

Alternatives To Felt Paper

Advances in roofing products have introduced several viable underlayment options that may outperform traditional felt. Synthetic underlayment is typically made from polypropylene or fiberglass-reinforced materials. It offers higher tear resistance, lighter weight, better slip resistance, and greater durability in wet conditions. Self-adhering peel-and-stick membranes provide a more robust moisture barrier, outstanding wind resistance, and excellent adhesion to the deck, though they come at a higher cost and require careful installation to avoid gaps.

Other considerations include rubberized asphalt underlayment, which remains flexible in cold weather and seals well around fasteners, and rain-impervious barriers designed for wildfire-prone regions. In some jurisdictions, building codes or manufacturer guidelines require or strongly recommend synthetic or peel-and-stick underlayments for certain roof pitches, climates, or shingle types. Always consult local codes and the shingle manufacturer’s installation instructions to determine acceptable underlayment options.

When Felt Paper Is Still A Practical Choice

There are circumstances where traditional felt paper remains a sensible choice. In regions with moderate climates, where installation speed and cost are prioritized, felt can be a practical option if it is installed correctly and the roof has a well-ventilated attic and good flashing details. For homeowners replacing worn roofing on an older house to maintain original construction methods, keeping felt in place can simplify the project while providing a familiar layer of protection. Some builders also use felt as a secondary backer in conjunction with a synthetic or peel-and-stick top layer to add redundancy.

Installation Considerations

When using felt paper, install with the following best practices to maximize performance. Overlap direction should be from bottom to top to promote shedding of water. Each sheet should be aligned with the deck boards to avoid exposed gaps, and fasteners should be placed per manufacturer guidelines to prevent tearing. In hot weather, avoid installing on a blazing roof to prevent premature tearing. After installation, shingles should cover the underlayment with proper overhangs at eaves and rakes. If using peel-and-stick membranes, ensure all seams are properly sealed and that the deck surface is clean and dry before application.

Code Compliance And Best Practices

Building codes in different U.S. regions vary on underlayment requirements. Some areas mandate synthetic underlayment due to better performance in heat, wind, and moisture resistance, while others permit traditional felt. Roofing manufacturers often specify compatible underlayment types for their shingles, which can influence warranty coverage. Adhering to local building codes and the shingle manufacturer’s installation instructions is essential for ensuring warranty protection and long-term roof performance.

Practical Guidance For Homeowners

For homeowners evaluating whether felt paper is necessary, the decision hinges on climate, budget, and performance priorities. If cost is a primary concern and local codes allow it, felt can be an adequate choice when installed correctly and paired with solid flashing and ventilation. If moisture risk, wind resistance, or climate extremes are significant concerns, synthetic underlayment or peel-and-stick membranes may offer superior protection and longer service life. Consulting with a licensed roofer who understands regional conditions can help tailor the best approach for a given residence.

Summary Of Key Points

Essential considerations

• Felt paper provides a secondary moisture barrier and a stable surface during installation but can wrinkle and absorb water over time.
• Synthetic underlayment and peel-and-stick membranes deliver greater durability, faster performance, and improved wind resistance in many climates.
• Local codes and shingle manufacturer guidelines determine the acceptable underlayment type and may influence warranty eligibility.
• Installation quality, ventilation, flashing, and roof age all impact the effectiveness of any underlayment choice.