Tar Sheet for Roof: A Comprehensive Guide to Tar Paper and Roofing Felt

Tar sheets, commonly known as tar paper or roofing felt, serve as a protective underlayment layer beneath shingles or other roofing materials. This article explains what tar sheets are, their types, benefits, installation steps, and how to choose the right product for different roof assemblies. It also covers maintenance tips and common mistakes to avoid, helping homeowners and builders make informed decisions about roofing underlayment.

What Is Tar Sheet For Roof

Tar sheet is a lightweight, flexible sheet material designed to act as a secondary barrier against moisture. Traditionally made from asphalt-saturated felt, modern options often blend fiberglass or organic fibers with asphalt or synthetic polymers. The primary function is to provide temporary and secondary protection from wind-driven rain during construction and after installation until the final roofing surface is installed.

In the United States, tar paper is widely used as an underlayment in various roofing systems, including asphalt shingle, metal, and tile roofs. The product varies in weight, typically expressed in pounds per 100 square feet (e.g., 15-lb, 30-lb, or 60-lb felt), and may include self-adhesive layers for improved seal against moisture.

Types Of Tar Sheets For Roof

The roofing industry offers several tar sheet variations, each with distinct performance characteristics. Understanding these differences helps in selecting the right underlayment for a given project.

• Traditional Asphalt-Saturated Felt: A fiberglass or organic foundation coated with asphalt. It is robust, affordable, and commonly used in standard residential roofs.
• Non-Permeable Underlayment: A higher-grade felt designed to resist water penetration more effectively, often used in climates with heavy rainfall or snow.
• Synthetic Roofing Underlayment: Made from polymers or composite materials, these sheets offer superior tear resistance, lighter weight, and better longevity than traditional felt.
• Self-Adhering (Self-Stop) Underlayment: Features a pressure-sensitive adhesive backing that adheres to the roof deck, creating a moisture barrier without nailing through the sheet.
• Felt With Permeable Overlay: Combines a felt layer with a permeable top surface to allow moisture to escape while protecting the roof deck during construction.

Benefits And Limitations

Tar sheets provide several practical benefits. They protect the roof deck during installation, reduce wind-driven moisture, and improve waterproofing when installed correctly. Self-adhesive underlayments offer easy installation and strong adhesion in cold or damp conditions. Synthetic underlayments often resist tearing and have longer lifespans, translating to fewer maintenance issues over time.

However, tar sheets have limitations. Traditional asphalt felts can deteriorate in high heat, become brittle in cold weather, and require proper sealing at all seams. Some products may weed out over time due to weathering or UV exposure if left exposed. In hot climates, asphalt-based felts may soften, while heavy foot traffic during installation can damage the material. The choice of underlayment should align with climate, roof slope, and local building codes.

Installation Considerations

Proper installation is crucial for the effectiveness of tar sheets. The process varies by product type, but general best practices remain consistent across most underlayments.

• Deck Preparation: Ensure the roof deck is clean, dry, and free of protrusions that could damage the underlayment.
• Spacing And Nailing: For traditional felt, lay sheets horizontally with a standard 2-inch nailing pattern on the ends and 4- to 6-inch along the field, according to manufacturer instructions. Self-adhesive products typically require you to remove a backing and press firmly to seal.
• Seam Treatment: Overlap seams according to product guidelines to prevent water penetration. Some self-adhesive products require no nails, while others may still require fasteners in exposed edges.
• Applies Before Shingles: The underlayment must be installed before the final roofing material and should be compatible with the chosen roof covering.
• Ventilation And Interruptions: Ensure proper ventilation during installation and address roof penetrations, such as vents and chimneys, with appropriate flashing and sealant.

When To Use Tar Sheets

Tar sheets are suitable in a variety of scenarios. They provide an affordable and effective moisture barrier in climate zones with moderate to heavy rainfall, snow, or wind-driven rain. Self-adhesive underlayments are advantageous in DIY projects or in cold climates where traditional nailing is challenging. Synthetic underlayments may be preferred for new construction requiring lighter weight and enhanced durability, especially on roofs with tight deadlines or complex layouts.

Weather, Climate, And Roofing Materials

Climatic conditions influence tar sheet performance. In hot, sunny regions, asphalt-based felts can become brittle or soften if not protected by the final roof covering. In coastal or humid areas, moisture resistance and vapor control become critical. For roofs with severe temperature fluctuations, synthetic or self-adhering underlayments offer superior performance and longevity. Always check local codes for requirements related to underlayment type and installation methods in the United States.

Maintenance And Longevity

Tar sheets typically do not require extensive maintenance once installed and covered with final roofing material. Periodic inspections after severe weather can identify damaged seams or punctures that require repair. If a roof deck shows signs of moisture intrusion or the underlayment appears damaged, it should be repaired or replaced to prevent leaks. When replacing shingles or other roofing materials, inspect the underlayment and re-fastening methods to ensure a durable seal.

Longevity depends on the product type and environmental exposure. Synthetic and self-adhering underlayments generally offer longer lifespans and better resistance to tearing, compared with traditional asphalt felts. Choosing a product with a proven warranty and a reputable brand helps ensure performance over time.

Choosing The Right Tar Sheet For Roof

Selecting the appropriate tar sheet involves evaluating several factors. These include climate, roof pitch, structural deck condition, and the final roofing system. Consider the following when choosing:

• Climate And Weather: High rainfall, snow, or heat exposure may favor synthetic or self-adhering underlayments.
• Roof Type And Slope: Steeper slopes may require more robust underlayments with higher tear resistance and secure fastening.
• Roofing Material Compatibility: Ensure the underlayment is compatible with shingles, metal, tile, or other coverings.
• Code Requirements: Local building codes may specify minimum underlayment performance or specific products.
• Ease Of Installation: Self-adhesive options can simplify installation, especially in challenging weather.

Common Mistakes To Avoid

Avoid costly errors by steering clear of common missteps. Do not install tar sheets over wet decks, as moisture can compromise adhesion and performance. Do not skip overlapping seams or fail to seal around roof penetrations. Ensure that accessories such as flashing, drip edges, and ridge caps are compatible with the chosen underlayment. Finally, neglecting local code requirements can lead to noncompliance and warranty issues.

Common Tools And Materials

Typical tools include utility knives, measuring tape, chalk line, roofing nails or staples (if using non-adhesive underlayment), roller or hand press for self-adhering sheets, and seam tape or sealant as recommended by the manufacturer. Materials to pair with tar sheets include roof decking, underlayment fasteners or adhesives, and the final roofing material such as asphalt shingles, metal, or tiles. Always follow manufacturer guidelines for best results.

Frequently Asked Questions

1. What is tar paper used for in roofing? It serves as a moisture barrier during construction and provides secondary protection under the final roof covering.
2. Can tar sheets be left exposed? Some self-adhesive underlayments are designed to be left exposed for a short period during building; however, many traditional felts should be covered promptly to prevent UV damage.
3. How long does tar paper last? Durability depends on the product and climate; synthetic and self-adhering underlayments generally last longer than traditional asphalt felts.

Key Takeaways

Tar sheets are a versatile and cost-effective underlayment option that remains relevant in modern roofing. By understanding the differences between traditional felt, synthetic, and self-adhering underlayments, homeowners and builders can choose a product that balances protection, installation ease, and long-term durability. Proper installation and adherence to local codes are essential to maximize the effectiveness of tar sheets and ensure a durable roof assembly.