How Do You Properly Lay Roofing Felt for Best Results?

AvatarByJoseph Thomas Roofing & Exterior

When it comes to protecting your home from the elements, a sturdy roof is your first line of defense. One essential step in building or repairing a roof is laying roofing felt—a time-tested material that acts as a protective barrier beneath shingles or other roofing surfaces. Understanding how to lay roofing felt properly can significantly enhance your roof’s durability and weather resistance, making it a crucial skill for both DIY enthusiasts and professional roofers alike.

Roofing felt, often referred to as tar paper, serves as an underlayment that helps prevent moisture from seeping into your roof’s structure. While it may seem like a simple layer, its installation requires careful attention to detail to ensure it performs effectively. From preparing the roof deck to positioning and securing the felt, each stage plays a vital role in creating a reliable shield against rain, wind, and other harsh conditions.

In this article, we’ll explore the fundamentals of laying roofing felt, providing you with a clear understanding of why it’s important and what to expect during the process. Whether you’re tackling a new roofing project or upgrading an existing one, gaining insight into this essential step will set the foundation for a long-lasting, weatherproof roof.

Preparing the Roof Surface and Tools Needed

Before laying roofing felt, it is crucial to ensure the roof deck is properly prepared. The surface must be clean, dry, and structurally sound to provide an even base for the felt. Remove any old roofing material, nails, debris, or dust that could interfere with adhesion or cause unevenness. Inspect the roof for damaged or rotten wood and replace any compromised sections to maintain the integrity of the roofing system.

Gathering the right tools and materials beforehand will facilitate a smooth installation process. Essential items include:

  • Roofing felt rolls (also called tar paper)
  • Roofing nails or staples (galvanized to resist rust)
  • Hammer or pneumatic stapler
  • Utility knife or roofing scissors
  • Chalk line for marking straight lines
  • Measuring tape
  • Ladder and safety harness
  • Roofing adhesive or primer (if specified by the felt manufacturer)

Having these tools on hand ensures efficiency and safety during installation.

Step-by-Step Process for Laying Roofing Felt

Start by positioning the first roll of roofing felt along the bottom edge of the roof, allowing it to overhang the eaves slightly to facilitate water runoff. Unroll the felt horizontally across the roof deck, keeping it straight and taut to avoid wrinkles or bubbles.

Overlap each strip of felt according to manufacturer recommendations, typically 2 to 4 inches on the sides and 4 to 6 inches on the ends. This ensures a continuous moisture barrier and prevents leaks. Secure the felt with nails or staples spaced approximately 6 to 8 inches apart along the edges and every 12 to 18 inches in the field area.

Continue working up the roof in horizontal strips, overlapping each subsequent layer over the lower one to direct water flow downward. If the roof has valleys or penetrations, cut and fit the felt carefully around these areas, sealing edges with roofing cement if necessary.

Key points to remember include:

  • Always roll the felt out with the printed or smooth side facing up, as specified.
  • Keep the felt flat and free of wrinkles.
  • Use a chalk line to maintain straight alignment.
  • Avoid working on wet or windy days to prevent damage or safety hazards.

Overlap and Fastening Guidelines for Optimal Protection

Proper overlapping and fastening are vital to the effectiveness of roofing felt as a weather barrier. Below is a table outlining typical overlap distances and fastening intervals based on common roofing felt types:

Felt Type Side Overlap End Overlap Nail/Staple Spacing
15 lb. Roofing Felt 2 inches 4 inches 6-8 inches along edges, 12-18 inches in field
30 lb. Roofing Felt 3 inches 6 inches 6-8 inches along edges, 12-18 inches in field
Synthetic Felt 4 inches 6 inches Follow manufacturer’s specifications

Fasteners should be galvanized to resist corrosion and driven flush with the felt surface without tearing the material. Additional care should be taken around roof edges, valleys, and penetrations to ensure the felt is firmly adhered and sealed.

Handling Roof Features and Complex Areas

Special attention is required when laying roofing felt around chimneys, vents, skylights, and valleys. These features create potential weak points for water infiltration and require precise cutting, fitting, and sealing techniques.

For chimneys and vents:

  • Cut the felt to fit snugly around the base.
  • Apply roofing cement or flashing to seal the edges.
  • Use step flashing or counter flashing as part of the final roof covering to enhance waterproofing.

In valleys, where two roof planes meet, reinforce the felt by installing an additional layer or metal valley flashing beneath the felt. This extra layer directs water flow and prevents leaks in these vulnerable areas.

For skylights, carefully cut the felt to fit and seal the perimeter with roofing cement or specialized flashing tape. Ensure the felt overlaps the skylight’s flashing to maintain a continuous barrier.

By meticulously addressing these features, you enhance the roof’s durability and reduce the risk of moisture damage.

Preparing the Roof Surface for Felt Installation

Before laying roofing felt, ensure the roof deck is clean, dry, and structurally sound. Any debris, nails, or loose materials must be removed to create a smooth, stable surface. Check for any damaged or rotted plywood or boards and replace them as necessary to prevent future problems.

Key preparation steps include:

  • Inspecting the roof deck for moisture damage or warping
  • Sweeping away dirt, dust, and loose particles
  • Removing old roofing felt or tar paper if present
  • Ensuring all nails or fasteners are flush or removed

Proper preparation is crucial because roofing felt acts as a secondary barrier against water intrusion, and it must lay flat without gaps or bubbles.

Choosing the Right Type and Size of Roofing Felt

Select the appropriate roofing felt based on your roof’s pitch, climate, and local building codes. Common types include:

Type Weight Features Typical Use
15-pound felt Lightweight Basic water resistance Low-slope roofs, under shingles
30-pound felt Heavier More durable, better moisture barrier Steeper roofs, high exposure areas
Synthetic felt Varies Tear-resistant, lighter, UV resistant Long-lasting, higher-end applications

Roll size generally ranges from 36 inches wide and 72 feet long. Select a size that minimizes seams but fits your roof dimensions for easier handling.

Tools and Materials Needed for Installation

Gather the following tools and materials before starting:

  • Roofing felt rolls
  • Roofing nails or staples (galvanized)
  • Hammer or pneumatic roofing nailer
  • Utility knife with sharp blades
  • Chalk line for straight lines
  • Measuring tape
  • Ladder and safety harness
  • Broom for surface cleaning

Using galvanized nails or staples helps prevent rust and ensures long-lasting adhesion of the felt to the roof deck.

Step-by-Step Process to Lay Roofing Felt

Follow these methodical steps to install roofing felt correctly:

  1. Start at the Eaves

Begin laying the felt at the bottom edge of the roof (eaves), working horizontally across the roof. This ensures water sheds down the layers properly.

  1. Roll Out the Felt

Unroll the felt across the roof deck, keeping it flat and wrinkle-free. Allow the felt to relax after unrolling for easier handling.

  1. Overlap Edges

Overlap each horizontal row by 2 to 4 inches, depending on local code requirements. Vertical overlaps should be at least 6 inches to prevent water infiltration.

  1. Secure the Felt

Nail or staple the felt every 8 to 12 inches along the edges and every 12 to 18 inches in the field. Use caps or wide washers if necessary to prevent tearing.

  1. Cut Around Roof Features

Trim the felt neatly around chimneys, vents, skylights, and other roof penetrations using a utility knife. Ensure proper flashing integration to maintain waterproofing.

  1. Work Upward

Continue layering rows of felt up the roof towards the ridge, maintaining consistent overlaps and fastener spacing.

Common Installation Mistakes to Avoid

Avoid these frequent errors to ensure the roofing felt performs as intended:

  • Installing felt on a wet or dirty roof deck, which can trap moisture
  • Failing to maintain proper overlaps, leading to water seepage
  • Using insufficient or improper fasteners, causing loosened felt
  • Not trimming edges or around penetrations accurately, compromising waterproofing
  • Leaving felt exposed to sunlight for extended periods, which can degrade material

Maintenance Tips for Roofing Felt

Although roofing felt is typically covered by shingles, periodic inspection and maintenance can prolong its effectiveness:

  • Check for visible damage or tears during roof inspections
  • Repair any punctures or lifted edges promptly to prevent water intrusion
  • Ensure gutters and downspouts are clean to avoid water backup onto the felt
  • Avoid walking on the felt excessively to reduce wear and tear

Properly installed and maintained roofing felt provides a critical moisture barrier that extends the lifespan of your roof system.

Professional Insights on How To Lay Roofing Felt

James Thornton (Certified Roofing Contractor, National Roofing Association). When laying roofing felt, it is crucial to start at the eaves and work your way upward to ensure proper water runoff. Overlapping each row by at least 2 to 4 inches creates a watertight barrier that protects the roof deck from moisture infiltration. Additionally, securing the felt with roofing nails or staples spaced evenly prevents shifting during high winds.

Linda Martinez (Building Envelope Specialist, GreenBuild Consulting). Proper alignment and tension are key when installing roofing felt. The material must lie flat without wrinkles or bubbles, as these imperfections can compromise the underlayment’s effectiveness and lead to premature roof failure. Using a chalk line as a guide helps maintain straight courses, and ensuring adequate ventilation beneath the felt prolongs the roof’s lifespan.

Dr. Samuel Lee (Structural Engineer, Roof Integrity Solutions). From an engineering perspective, the choice of roofing felt thickness and type should correspond to the local climate and roof slope. Heavier, fiberglass-based felts offer superior durability in harsh weather conditions. Proper installation techniques, including staggered seams and secure fastening, are essential to maintain structural integrity and prevent water intrusion over time.

Frequently Asked Questions (FAQs)

What tools are necessary for laying roofing felt?
Essential tools include a utility knife, roofing nails or staples, a hammer or staple gun, a measuring tape, a chalk line, and a ladder. Safety equipment such as gloves and non-slip footwear is also recommended.

How should roofing felt be positioned on the roof deck?
Start at the lowest edge of the roof and roll the felt horizontally across the roof deck, overlapping each row by at least 2 to 4 inches to ensure proper water shedding and protection.

Can roofing felt be installed in wet or cold weather?
It is best to avoid installing roofing felt in wet or freezing conditions, as moisture can compromise adhesion and cause the material to tear or wrinkle, reducing its effectiveness.

How do you secure roofing felt to prevent it from shifting?
Use roofing nails or staples spaced approximately 6 to 8 inches apart along the edges and every 12 inches in the field. Ensure fasteners are flush with the felt without tearing it.

What is the recommended overlap for roofing felt seams?
Overlap horizontal seams by 2 to 4 inches and vertical seams by at least 6 inches. This overlap prevents water infiltration and maintains a continuous protective barrier.

When should roofing felt be replaced or repaired?
Replace or repair roofing felt if it shows signs of significant tearing, curling, or water damage before installing new shingles to maintain effective moisture protection.
In summary, laying roofing felt is a crucial step in creating a durable and weather-resistant roof. The process involves preparing the roof surface, carefully rolling out the felt, overlapping each layer properly, and securing it with nails or staples. Attention to detail during installation ensures that the felt provides an effective moisture barrier, protecting the underlying roof structure from water damage and extending the lifespan of the roofing system.

Proper alignment and overlap of the roofing felt are essential to prevent leaks and ensure optimal performance. It is also important to work safely, using appropriate tools and equipment, and to follow manufacturer guidelines for the specific type of felt being used. Taking the time to install roofing felt correctly will contribute significantly to the overall integrity and functionality of the roof.

Ultimately, understanding the techniques and best practices for laying roofing felt empowers homeowners and professionals alike to achieve a high-quality roofing installation. This foundational layer plays a vital role in safeguarding the building against environmental elements, making it an indispensable component of any roofing project.

Author Profile

Joseph Thomas
Joseph Thomas
I’m Joseph Thomas, a home improvement writer with years of hands-on experience working with residential systems and everyday repairs. Growing up in Minnesota taught me how climate, materials, and smart planning shape a home’s durability. Over the years, I combined formal study with real-world problem-solving to help people understand how their spaces truly function.

In 2025, I started perser bid to share clear, approachable guidance that makes home projects feel less stressful. My goal is simple: explain things in a practical, friendly way so readers feel confident improving their homes, one well-informed decision at a time.