Nails for Roof Felt: A Definitive Guide to Choosing and Installing Roofing Nails

Roof felt, or underlayment, is a critical layer that protects a roof deck from moisture and wind-driven rain. Selecting the right nails for roof felt ensures secure attachment, prevents leaks, and extends the life of the roofing system. This guide covers types, sizes, materials, installation techniques, and common pitfalls to help homeowners and contractors choose nails for roof felt with confidence.

What Are Nails For Roof Felt?

Nails for roof felt are specialized fasteners designed to secure felt paper or synthetic underlayment to roof decks. They must resist pull-out from wind uplift, corrosion from moisture, and potential damage from installation tools. The nails typically feature a broad, flat head to prevent tearing the felt and a sharp point to penetrate decking cleanly. In American practice, roofing nails, galvanized nails, and stainless steel variants are commonly used depending on climate, deck material, and roofing type.

Types Of Nails For Roof Felt

Understanding nail types helps match the installation environment and local building codes. The main categories are:

• Roofing Nails — Specifically designed for roofing underlayment and shingles. They have a wide head and a slender shaft with a ring or smooth finish, reducing pull-out and facilitating quick installation with a hammer or nail gun.
• Coil Roofing Nails — Used with pneumatic guns for fast, uniform attachment. They come in strips for coil tools and often feature ring shanks that improve holding power in underlayment and shingles alike.
• Galvanized Nails — Coated with zinc to resist rust and corrosion, suitable for most climates. They are a cost-effective option for untreated or treated plywood and OSB decks.
• Stainless Steel Nails — Higher corrosion resistance and longevity, ideal for coastal or high-humidity environments. They reduce the risk of staining or staining of adjacent materials.
• Aluminum Or Copper Nails — Less common but used in specialty projects where corrosion resistance and minimal staining are priorities, often in premium or historic applications.

Choosing The Right Nail Size And Material

Selection depends on deck material, underlayment type, climate, and fastener exposure. General guidelines:

• Diameter — Typical roofing nails range from 0.120 to 0.135 inches for felt underlayment. A larger diameter increases pull-out resistance but may risk splitting thinner decking.
• Length — For plywood or OSB, 1-1/4 to 1-3/4 inch nails are common. In areas with thick framing or where multiple layers are used, longer nails ensure solid anchorage.
• Head Type — A wide, flat head helps prevent tearing of the felt. Look for collars or ringed heads that improve withdrawal resistance in windy areas.
• Coating — Galvanized coatings are standard for most climates. Stainless steel is preferred in coastal zones with salt exposure.
• Underlayment Type — Heavier synthetic underlayments may require larger or specialized nails to prevent tearing and ensure secure seating.

Local building codes may specify nail type or material for felt installation, so checking with the jurisdiction is essential. For reroofing projects, match the existing fasteners to preserve warranty terms and performance.

Installation Best Practices

Proper technique ensures maximum performance and minimizes damage to the underlayment. Key steps include:

• Surface Preparation — Ensure the roof deck is clean, dry, and free of protrusions. Remove old nails or sharp debris that could tear the felt.
• Tool Selection — Use a hammer for hand-nailing or a pneumatic nail gun for coil roofing nails. For synthetic felts, use the correct nail length and avoid over-penetration that could weaken the deck.
• Driving Technique — Drive nails perpendicular to the surface to avoid bending or skiving the felt. Do not overdrive; the nail head should sit flush with the felt without tearing.
• Pattern And Spacing — Typical patterns place nails every 6 to 8 inches along the edges and 12 to 18 inches in the field, depending on wind loads and code requirements. Start at the bottom edge and work upward to minimize water entry paths.
• Edge Nailing — Place nails 1 inch from the edge to reduce edge tear. For high-wind areas, reduce spacing along eaves and rakes to improve uplift resistance.
• Seal And Inspect — After fastener installation, inspect for loose nails, misalignment, or torn felt. If a nail is loose, re-nail with a new one and inspect neighboring nails for stability.

Common Mistakes And Troubleshooting

Avoiding common errors protects the roof’s integrity and the underlayment’s performance.

• Using Inappropriate Nail Size — Nails that are too short or thin may pull out in high winds, leading to leaks.
• Overdriving Nails — Pushing nails too deep can compress or tear felt, creating weak spots that leak.
• Incorrect Pattern — Irregular nail spacing can create wind uplift paths and increase the chance of water intrusion.
• Improper Storage — Storing nails in damp conditions can lead to corrosion before installation.
• Ignoring Local Codes — Codes may mandate specific materials or patterns for felt installation in certain regions.

Maintenance And Longevity

Proper maintenance extends the life of both the underlayment and the nails. Consider these practices:

• Regular Inspections — After severe weather, inspect the roof edge, hips, and valleys for loose nails or tears in the felt.
• Replacement Protocols — If felt shows signs of wear or damage, replace the affected sections with matching nails and underlayment material to maintain a continuous protective layer.
• Corrosion Monitoring — In coastal or humid regions, monitor for rust around fasteners and plan periodic replacements with corrosion-resistant options.
• Warranty Compliance — Follow manufacturers’ guidelines for nail material and installation methods to keep warranties valid.
• Eco-Friendly Considerations — When possible, choose corrosion-resistant, recyclable fasteners to reduce environmental impact without compromising performance.