30 pound felt paper, commonly known as roofing tar paper, is a durable underlayment used in residential and commercial roofing and siding projects. This guide explains what it is, where it’s used, installation best practices, advantages and drawbacks, and how to choose the right type for a successful build or repair. Readers will gain practical insights for selecting, installing, and maintaining 30 pound felt paper to protect buildings from moisture and wind-driven elements.
What Is 30 Pound Felt Paper?
30 pound felt paper is a asphalt-impregnated underlayment made from a layer of organic felt or fiberglass that has been saturated with asphalt and then sized to a weight of around 30 pounds per 100 square feet. It acts as a secondary barrier beneath shingles or siding, helping to shed moisture that bypasses the primary roof or wall coverings. The material is typically sold in rolls and is easier to handle than heavier underlayments while still offering robust tear resistance and puncture protection.
Uses And Applications
Typical applications for 30 pound felt paper include roofing and wall assemblies where an additional moisture barrier is desired. It is commonly used under asphalt shingles, wood shingles, and some metal roof systems. In colder climates, it can help reduce wind-driven moisture infiltration. It may also serve as a temporary protection during construction or repairs. While newer synthetic underlayments are popular, 30 pound felt paper remains a budget-friendly, time-tested option with proven performance when installed correctly.
Installation Tips
Proper installation is essential for optimal performance. Key steps include:
- Surface preparation: Ensure the roof deck or wall shear plane is clean, dry, and free of protrusions that could damage the underlayment.
- Overlap guidelines: Install with standard overlaps, typically 19 to 24 inches on horizontal surfaces and 6 to 8 inches for vertical seams, following manufacturer recommendations.
- Nailing and fasteners: Use corrosion-resistant nails or staples per the product spec. Place fasteners along the edges at prescribed intervals to prevent wind uplift.
- Seam treatment: For exposed areas, apply compatible sealant or self-sealing overlaps if required by the manufacturer to reduce moisture infiltration.
- Ventilation and drainage: Ensure proper attic ventilation and roof drainage to minimize moisture buildup behind the underlayment.
- Compatibility: Verify compatibility with the top-layer roofing material and any existing moisture barriers.
Pros And Cons
Pros:
- Cost-effective compared to many synthetic underlayments.
- Easy to install with basic tools and common roofing practices.
- Provides a secondary moisture barrier that can protect decking during construction.
- Good puncture resistance and rotting protection when installed properly.
Cons:
- Less durable in extreme UV exposure and high temperatures than some synthetic options.
- Can deteriorate in prolonged standing moisture or snowfall without proper drainage.
- Higher risk of tearing during installation or after weather events if not handled carefully.
- Less tolerant of long-term exposure to moisture than advanced synthetic or rubberized membranes.
Choosing The Right Grade And Age
When selecting 30 pound felt paper, consider:
- Weight consistency: Confirm the product truly weighs around 30 pounds per 100 square feet and check for uniform thickness across rolls.
- Material base: Organic felt options are more common in older homes; fiberglass-based felts offer improved tear resistance and moisture tolerance.
- Age and storage: Fresh rolls perform better; avoid products exposed to prolonged heat, direct sunlight, or moisture in storage.
- Environmental conditions: In hot, sunny climates or roofs with high UV exposure, consider higher-performance underlayments or synthetic alternatives for longer life.
- Code and manufacturer guidelines: Ensure the chosen underlayment meets local building codes and the roofing system specifications.
Maintenance And Longevity
Maintenance for 30 pound felt paper centers on proper installation and protection from weather exposure during construction. After installation, care includes ensuring that roof vents and attic spaces remain unobstructed to prevent moisture buildup behind the underlayment. If visible damage appears after storms, inspect for tears or lifted edges and repair promptly to preserve the barrier. For longevity, plan for eventual replacement if the roof system is updated or if synthetic underlayments are introduced during a retrofit.
Alternatives To 30 Pound Felt Paper
Alternatives include:
- Synthetic underlayments: Lightweight, highly resistant to moisture, and often quicker to install with improved longevity.
- Rubberized asphalt membranes: Self-adhesive and highly resistant to water infiltration, suitable for high-moisture environments.
- Liquid-applied membranes: Provide seamless coverage, especially for irregular roof decks or complex transitions.
- Building wrap or housewrap: Used primarily on walls to provide weather barriers, sometimes combined with dedicated roof underlayment in certain assemblies.
Buying Guide And Tips
To buy the right 30 pound felt paper product, consider:
- Brand and warranty: Look for reputable brands offering warranties that align with the roof system plan.
- Local climate suitability: Choose a product designed to perform under your region’s temperature and precipitation patterns.
- Compatibility: Ensure the underlayment is compatible with the roof covering and any existing moisture barriers.
- Roll dimensions: Check roll width and length to minimize waste and handling effort on large roofs.
- Storage considerations: Buy from suppliers that store products in shaded, dry conditions to preserve quality.
Installation Scenarios And Best Practices
For new construction or major remodels, a layered approach may be used: roof deck, 30 pound felt paper, and then shingles or other top coverings. In retrofit projects, ensure the underlayment is compatible with existing membranes and that any necessary ventilation or drip edge components are incorporated. In regions with heavy snowfall or high wind, consider enhanced underlayment options or additional protective layers to improve resilience against weather events.
Summary Of Key Points
- 30 pound felt paper serves as a cost-effective secondary moisture barrier for roofing and siding assemblies.
- Correct overlap, fastening, and protection from moisture are critical to performance.
- Weighs around 30 pounds per 100 square feet; variations exist between felt bases and manufacturers.
- Consider alternatives like synthetic underlayments for longer life in extreme climates.