90 Weight Roofing Paper: Ultimate Guide for Roofing Felt

90 weight roofing paper refers to a heavy-duty roofing underlayment commonly used to provide an extra layer of protection beneath the final roofing surface. This guide explains what 90 weight roofing paper is, how it differs from lighter felts, where it’s best used, installation considerations, and how to assess its performance in modern roofing systems.

What Is 90 Weight Roofing Paper

90 weight roofing paper is a traditional asphalt-saturated felt underlayment designed to shield rooftops from moisture during construction and to add a secondary water barrier after installation. It is typically sold per roll and is measured as weight per 100 square feet. At 90 pounds per 100 square feet, this material sits between standard 30‑pound felt and heavier commercial underlayments, offering greater tear resistance and durability. While less common in new builds today, it remains relevant in certain climates and building codes that require extra protection during framing and weather exposure.

How It Differs From Lighter Felts

Lighter felts, such as 15‑pound and 30‑pound options, provide basic moisture protection and act mainly as a temporary barrier during construction. In contrast, 90 weight roofing paper delivers higher tear strength, puncture resistance, and a more robust barrier against wind-driven rain. The tradeoff is increased weight and stiffness, which can affect handling and installation, especially on steep roofs or when working alone. Contractors may choose 90 weight felt in areas with heavy rain exposure or where building codes specify a heavier underlayment.

Applications And When To Use It

90 weight roofing paper is well-suited for:

• Rooftops with prolonged exposure to weather during construction
• Regions prone to strong winds or heavy rainfall
• Roofing systems that require an added secondary moisture barrier
• Older homes where retrofitting with heavy underlayment is recommended

In new construction, many builders opt for modern synthetic underlayments or self-adhering membranes, which offer superior performance and easier installation. However, 90 weight felt remains a viable option when code or project specifications call for a heavier traditional material.

Installation Considerations

Proper installation is essential to maximize performance. Follow these guidelines:

• Lay the felt with the correct grain orientation and ensure the surface is clean and dry.
• Shingle the felt with proper overlaps, typically 2 to 4 inches depending on wind and climate conditions.
• Use smooth, even fasteners or nails to prevent tearing; avoid over-tightening which can damage the paper.
• Inspect for wrinkles or air pockets that could trap moisture and cause damage.
• Be mindful of weather; install during dry, moderate conditions to avoid reducing the felt’s effectiveness.
• In areas with high winds or storm risk, consider additional fastening or transitioning to a synthetic or self‑adhering underlayment for enhanced security.

Advantages And Limitations

Advantages

• Enhanced tear and puncture resistance compared with lighter felts
• Cost-effective option for projects requiring heavy underlayment
• Acts as a secondary moisture barrier if the primary roof deck is compromised

Limitations

• Heavier and less forgiving to handle, increasing labor effort
• Less compatible with modern roof systems that rely on synthetic or self‑adhering membranes
• May require more precise installation to prevent buckling on irregular roof planes

Durability, Longevity, And Performance

When installed correctly, 90 weight roofing paper performs as a reliable secondary barrier during construction and initial weather exposure. Its durability helps resist tearing from wind-blown debris and foot traffic on steep pitches. Over the long term, the protection it provides depends on proper nailing patterns, overlaps, and the overall roofing assembly. In climates with rapid temperature swings or persistent moisture, pairing traditional felt with a modern top layer—such as an asphalt shingle underlayment or synthetic sheet—can improve overall performance.

Maintenance, Inspection, And Replacement

Periodic inspection is important, especially on roofs that are under construction or exposed to the elements for extended periods. Look for:

• Gaps, tears, or loosened sections from wind or foot traffic
• Water staining or dampness indicating compromised seams
• Punctures from nails or fasteners that may have pierced the paper

If damage is detected, assess the scope. Localized issues can often be repaired with replacement strips, but extensive damage may require full underlayment replacement prior to final roof installation. Always follow local building codes and manufacturer recommendations for repair intervals and compatible materials.

Comparison With Other Underlayments

Understanding how 90 weight roofing paper stacks up against common options helps in decision making:

• 15 Pound Felt: Lighter, easier to handle, less protection against weather exposure, commonly used for temporary protection.
• 30 Pound Felt: Standard choice for many projects, balanced protection and installability.
• Synthetic Underlayments (non‑bitumen): Higher tear resistance, quick drying, and superior moisture handling; preferred for modern roofs.
• Self-Adhering Membranes: Excellent moisture barrier, excellent wind resistance, but typically more expensive and require careful installation.

Cost Considerations

Costs for 90 weight roofing paper vary by region and supplier. In general, heavier felts are priced higher than light felts but remain cheaper than many synthetic or self-adhering underlayments. When evaluating cost, consider labor, installation difficulty, climate, and local building codes. If a project requires extra protection during construction, the additional upfront cost may be justified by reduced risk of weather-related damage.

Code And Standards

Building codes influence underlayment choices. Some jurisdictions restrict or specify underlayment types in certain roofing assemblies. It is essential to verify local codes, as well as manufacturer guidelines, to ensure compliance and warranty eligibility. The 90 weight option often appears in retrofit scenarios or projects with particular wind or moisture considerations.

Selecting The Right Underlayment For A Roof

Choosing between 90 weight roofing paper and alternatives depends on climate, roof pitch, and construction timeline. Consider:

• Local weather patterns and exposure duration during construction
• Roof pitch, complexity, and anticipated wind loads
• Compatibility with final roofing material and membrane underlayment options
• Cost, handling ease, and installer experience

For homeowners and builders, consulting with a licensed contractor who understands local conditions and code requirements can help determine whether 90 weight roofing paper is the optimal choice or if a modern synthetic or self-adhering underlayment provides better long-term performance.