Applying Tar Paper to Roof

The process of applying tar paper, or roofing felt, is a foundational step in building a durable roof. Proper installation protects underlying materials from moisture, helps with insulation, and creates a smooth surface for shingles or other roofing materials. This guide covers preparation, materials, step-by-step installation, and maintenance considerations to ensure a reliable, long-lasting roof for American homes.

What Is Tar Paper And Why It Matters

Tar paper, commonly known as roofing felt, is a heavy paper impregnated with bitumen or asphalt. It is laid over roof decking to provide a moisture barrier and to help with shingle alignment. There are different weights and types, including standard felt and synthetic variants. The choice depends on climate, roof pitch, and local building codes. Properly applying tar paper minimizes water intrusion, reduces wind-driven leaks, and extends the life of the roofing system.

Tools And Materials

Gathering the right tools and materials simplifies installation and enhances accuracy. Key items include:

• Tar paper or roofing felt (typically 15-lb or 30-lb, or synthetic felt)
• Roofing nails or cap nails with large heads
• Nail gun or hammer
• Utility knife or scissors for cutting
• Chalk line and a straightedge
• Roofing adhesive or sealant (where required by local code)
• Measuring tape and ladder or scaffolding
• Trowel or brush for sealant application (if using asphalt-based sealants)

Note: Always check local building codes and manufacturer recommendations for weight, overlap, and fastening requirements specific to your region and roof type.

Preparation And Surface Check

Successful tar paper installation starts with a clean, dry, and sound substrate. Steps include:

• Inspect roof decking for damage, rot, or loose boards; replace as needed.
• Remove protrusions or secure existing materials that might interfere with laying tar paper.
• Ensure the roof surface is dry; apply tar paper only in dry conditions.
• Install a drip edge along eaves for water control and to give a clean edge for the felt.
• Lay out courses to determine overlaps; standard practice is a minimum 2-inch horizontal overlap and 19-inch vertical overlaps depending on width of roll and local code.

Step-By-Step Installation

Follow these steps to apply tar paper effectively while maintaining consistency and weather resistance:

1. Position the first row along the eave with the bottom edge hanging over the drip edge by a small amount to guide water runoff.
2. Fasten the felt using nails or a pneumatic nail gun at regular intervals, typically about 6 to 8 inches apart along the edges and 12 inches in the field, as per manufacturer guidance.
3. Unroll and align subsequent courses with a horizontal overlap of at least 2 inches and a vertical overlap of about 19 inches, ensuring no gaps or wrinkles.
4. Seal seams along the overlaps with roofing cement or manufacturer-approved seam tape if required by the product type.
5. Work from bottom to top, ensuring each course remains flat and free of air pockets that can trap moisture.
6. Guard against wind uplift by applying additional fasteners near ridge lines or in high-wind areas according to code requirements.
7. When reaching roof hips, valleys, or around dormers, cut the tar paper carefully to fit, maintaining proper overlaps and sealing any exposed edges with appropriate sealant.

Weather And Climate Considerations

Weather greatly affects tar paper performance. In high humidity or impending rain, tar paper can shrink or warp, reducing adhesion. Ideal conditions are dry, mild temperatures. In cold climates, allow sufficient curing time for any asphalt-based sealants between layers. In hot climates, avoid applying if surface temperatures exceed recommended limits, which can cause premature wrinkling. For reroofing projects, consider synthetic roofing underlayment in place of traditional tar paper for superior tear resistance and longevity.

Sealing And Edge Treatments

Proper sealing at edges and penetrations is critical to prevent leaks. Common practices include:

• Applying a continuous bead of roofing cement along seams and at valleys, following the product instructions.
• Using seam tape on synthetic felts to reinforce critical joints.
• Protecting around penetrations (vents, chimneys) with flashing and compatible sealants to maintain a watertight seal.

Edge protection, drip edge alignment, and proper sealing reduce water intrusion and extend roof life.

Safety And Handling

Roof work carries fall and heat risks. Essential safety practices include:

• Using a fall-arrest system or guardrails where required by local regulations.
• Wearing non-slip footwear, gloves, and eye protection.
• Managing ladders and scaffolding securely and keeping work areas free of debris.
• Handling hot asphalt products with care to avoid burns; allow sealed products to cool during application in hot weather.

Maintenance And Longevity

Tar paper contributes to roof longevity when properly installed and maintained. Consider these maintenance tips:

• Inspect the roof after severe storms for displaced felts or gaps at edges and around penetrations.
• Replace degraded or torn sections promptly to maintain the moisture barrier.
• Keep gutters clear to prevent water backup that can lead to edge lift and moisture intrusion.
• Document installation details, including roll weight, overlap measurements, and fastener type for future repairs or inspections.

Common Mistakes To Avoid

Awareness of typical errors helps improve outcomes. Common mistakes include:

• Using insufficient overlaps, which can lead to leaks at seams.
• Installing tar paper on damp or dusty decking, reducing adhesion.
• Overlooking ventilation or drainage issues that can stress the underlayment system.
• Skipping edge sealing where wind-driven rain can penetrate under the roof covering.

When To Call A Professional

Tar paper installation can be DIY-friendly for small repairs or straightforward roofs, but complex layouts, steep pitches, or damaged decking may require professional help. A licensed roofing contractor can ensure code-compliant underlayment installation, proper flashing, and a sound base for the final roofing material.