A hurricane tie (also known as a hurricane clip or strap) is a specialized metal connector designed to secure the roof structure to the wall frame. These connectors resist uplift forces created by high winds that attempt to lift the roof off the house. The connection’s integrity depends entirely on the fasteners used, making the correct nail size critical for performance. Using the wrong nail size, type, or length can significantly reduce the connector’s load capacity, compromising the home’s defense against severe weather.
The Critical Nail Specifications: Size, Diameter, and Length
The most common nail sizes specified for hurricane ties are the 8d and 10d structural connector nails. For structural connectors, the traditional penny size designation (“d”) is often misleading. A standard 8d common nail is typically 2.5 inches long, which is too long for most hurricane tie applications on standard framing.
The industry standard is a shorter, specialized fastener, most often an 8d x 1-1/2 inch nail. This specific length is engineered to penetrate the metal connector and the first wood member, such as a rafter. This prevents the nail from protruding excessively through the wood, which could reduce the connection’s ability to resist uplift or cause the wood member to split.
While length is important for proper installation, the nail’s diameter is the primary factor determining its shear strength, which is the force required to cut the nail. The required diameter for the 8d structural connector nail is typically 0.131 inches. Some heavy-duty ties may require a 10d connector nail, which has a slightly larger diameter of 0.148 inches.
The manufacturer’s load tables are based on these precise diameter and length specifications, not just the penny designation. Therefore, selecting a nail that matches the specified diameter is more accurate than relying solely on the “8d” or “10d” label. Using a thinner nail, even if it is the correct length, will significantly reduce the tested uplift capacity of the hurricane tie.
Beyond Size: The Importance of Nail Type and Penetration
The material and design of the fastener are crucial for maintaining the connection’s structural integrity. Only structural connector nails, sometimes called joist hanger nails, should be used with hurricane ties. These nails are manufactured from hardened steel to provide the necessary shear strength to withstand the lateral and uplift forces generated during a storm.
Avoid using common box nails, drywall nails, or roofing nails, as these lack the necessary material strength and diameter for structural applications. The use of a non-structural nail will void the tie’s load rating and create a weak point in the roof-to-wall connection.
Corrosion resistance is another requirement, especially in coastal or high-humidity environments. Structural connector nails must have a protective coating, such as Hot-Dip Galvanized (HDG) or a proprietary coating like ZMAX. This finish prevents rust, which can quickly compromise the nail’s diameter and its shear strength over time.
The correct nail length ensures proper penetration depth into the wood members. The goal is to achieve double shear nailing, where the nail passes through the metal tie, the first wood member, and fully into the second wood member. This maximizes the surface area of the nail resisting the load, providing the highest possible capacity. The shorter 1-1/2 inch nail is often specified to ensure maximum penetration without the tip exiting the side of a standard 2x lumber piece.
The Final Authority: Manufacturer Specifications and Local Codes
While general guidelines exist, the manufacturer is the authority on the correct nail size. Every structural connector is tested and rated based on a specific fastener, and the published load capacity is only valid if that exact nail is used. The required nail size, including the diameter and length, is often stamped directly onto the metal tie or listed in the product’s technical literature.
Before purchasing any fasteners, the builder or homeowner must consult the local building department. Building codes often supersede general recommendations and may have specific requirements for wind-prone areas. For example, some regions have adopted specific rules, such as the “third nail” requirement, which mandates a certain number of fasteners to qualify for insurance discounts or meet minimum safety standards.
The nail’s protective finish must match the finish of the hurricane tie to prevent a chemical reaction called galvanic corrosion. A ZMAX-coated tie, for instance, should be installed with ZMAX-coated nails to avoid the accelerated deterioration that occurs when dissimilar metals are in contact. Following the manufacturer’s instructions and local code requirements guarantees the connection will perform as designed during a high-wind event.