Building paper and roofing felt are common terms in residential construction, often used to protect roofs during and after installation. Understanding their differences, uses, and performance helps homeowners and contractors choose the right material for weather protection, durability, and cost. This article compares building paper and roofing felt, explains where each is appropriate, and highlights installation considerations to improve long-term roof performance.
What They Are and How They Are Used
Building paper, also known as tar paper or paper felt, is a traditional asphalt-impregnated paper used as an underlayment on roofs. It provides a temporary barrier against moisture during construction and can offer some wind resistance after installation. Roofing felt refers to a broader category that includes mat-based underlayments made from cellulose, fiberglass, or synthetic fibers coated with asphalt. Roofing felt is designed specifically to endure weather exposure during and after installation, forming part of the roof’s secondary barrier.
Key distinction: Building paper is often a lighter, more traditional option primarily for moisture management during construction, while roofing felt encompasses durable underlayments designed for ongoing weather protection.
Material Differences And Performance
Material composition drives performance. Building paper is typically a heavyweight paper that saturates with asphalt, creating a moisture barrier. Roofing felt can be synthetic or glass-fiber reinforced, which improves tear resistance and longevity while maintaining flexibility in cold weather. Synthetic underlayments may offer superior UV resistance and faster installation. The choice affects wind uplift resistance, drip edge behavior, and overall roof protection.
Performance implications: Roofing felt generally provides better long-term protection against leaks and wind uplift, while building paper is more limited in durability and weather exposure tolerance.
Applications And Typical Installation Scenarios
Traditionally, building paper was installed as the first layer over roof sheathing in Nailing or shingle-over roof systems, followed by another layer of underlayment. Today, modern roofs often use synthetic roof underlayments that substitute for traditional roofing felt. Building paper remains common in some retrofit or historical renovation projects where traditional methods are preferred. Roofing felt is preferred for new construction where code or manufacturer guidelines specify an underlayment with specific tear resistance, water resistance, and wind uplift performance.
Best use cases: Building paper is mostly seen in renovations or where a traditional assembly is specified. Roofing felt or synthetic underlayments are standard for new homes and most modern roofing systems.
Weather Resistance, Breathability, And Lifespan
Weather resistance depends on asphalt saturation, thickness, and the type of fibers. Building paper tends to degrade faster in prolonged exposure to sun and moisture, reducing its protective value if exposed. Roofing felt, especially high-quality synthetic or fiberglass-based products, offers longer service life and better tear resistance. Breathability matters for attic moisture management; some underlayments are designed to allow vapor diffusion to varying degrees, reducing condensation risk. Lifespan varies widely by climate, installation quality, and manufacturer specifications.
Practical takeaway: For severe climates or high-waitaer exposure, choose a roofing felt or synthetic underlayment with proven UV resistance and extended warranty. Building paper is less durable for long-term exposure.
Installation Considerations
Correct installation is crucial for underlayment performance. Building paper is typically stapled or nailed in place, with laps overlapped at nominal sealing lengths. Roofing felt requires careful alignment of seams, typically with specific overlap percentages to prevent water penetration. Fastener type and spacing matter; improper fasteners can lead to gaps or wind uplift. In modern practice, manufacturer installation guidelines should be followed, including airflow considerations and compatibility with roof coverings such as shingles or tiles.
Practical tip: Always verify compatibility with the chosen roof covering and local building codes. Poorly installed underlayment undermines roof performance regardless of material choice.
Cost, Availability, And Accessibility
Building paper generally costs less per square foot than high-end roofing felt or synthetic underlayments. Availability tends to be wide for traditional tar papers, but product choices may be limited by local supply chains. Roofing felt and synthetics offer a broader range of performance tiers, including lightweight and heavy-duty options. For projects on a budget or with older homes, building paper may be a viable option, though potential long-term costs from increased maintenance should be considered.
Decision factor: Weigh upfront costs against expected lifespan, maintenance needs, and warranty terms when selecting underlayment material.
Environmental Impact And Disposal
Underlayment materials contribute to the environmental footprint of a roof. Building paper uses paper fibers with asphalt saturation, which can be less favorable for recycling in some regions. Roofing felt, especially synthetic versions, may offer improved durability with less frequent replacement, potentially reducing waste over time. Local disposal guidelines apply, and some municipalities provide specific recycling or disposal streams for asphalt-impregnated products.
Eco-conscious note: When possible, select underlayments with longer lifespans and recycle options at the end of service life, and follow local guidelines for disposal.
Summary Of Key Points
- Building paper is a traditional, asphalt-saturated paper underlayment with limited long-term weather exposure protection.
- Roofing felt encompasses modern underlayments (including synthetic options) designed for durable moisture protection and wind resistance.
- Choose based on climate, roof type, and manufacturer guidelines; synthetic underlayments generally outperform traditional building paper in durability.
- Installation quality and compatibility with roof coverings determine overall effectiveness more than material choice alone.
- Cost vs. lifespan should guide selection, with attention to local codes and warranty requirements.
Practical Comparisons At A Glance
| Aspect | Building Paper | Roofing Felt |
|---|---|---|
| Material | Asphalt-saturated paper | Fiberglass/synthetic or cellulose with asphalt |
| Durability | Lower in prolonged exposure | Higher; designed for long-term exposure |
| Weather Protection | Temporary barrier during construction | Primary or secondary weather barrier |
| Breathability | Limited | Varies by product; some are engineered for vapor diffusion |
| Installation | Simple, overlaps with fewer complex requirements | |
| Cost | Generally lower upfront | Higher upfront, broader performance options |
| Best For | Renovations, traditional builds | New construction, modern roofs, harsh climates |
In summary, selecting between building paper and roofing felt hinges on performance expectations, climate, and roof system design. Modern practice tends to favor synthetic underlayments for their durability and ease of installation, while building paper remains a valid option in certain renovation contexts or where traditional methods are specified. Always follow current building codes and manufacturer guidelines to ensure optimal roof protection and longevity.