Rood decks attach to the top of rafters or joists to reinforce the roof structure and form a solid surface for installing roof coverings. However, without sufficient fastening, decking materials might loosen under heavy winds or shift and cause damage to the roof structure. Nailing schedules dictate the nailing requirements for roof decking materials, such as sheet goods or solid planks. Nailing schedule prescriptions include the nails' spacing, installation pattern and size. Ultimately, you must look to your local building authority for a roof nailing schedule. An understanding of common nailing schedules for roof decking prepares you to estimate and plan a roof installation or renovation.
About Roof Decks
A roof's deck or "sheathing" is a layer of material between a roof's structural framing members, such as rafters or joists, and the roof's covering material, such as shingles or panels. Sheet goods are the most common materials for roof decks in conventional wood frame construction. Sheet goods used for roof decking include plywood and oriented strand board, or OSB. Before the widespread adoption of sheet goods for roof sheathing, solid wood planks were the most common decking materials.
Nailing Schedule for Plywood Sheathing
Structural plywood and OSB sheathing typically share a nailing schedule. At least two edges of a plywood or OSB sheet must align with a roof joist or rafter; these edges are called the perimeter. The center of the sheet is called the field. You must drive all sheathing fasteners through the sheet material and into underlying rafters or joists. Along the perimeter of plywood or OSB sheathing, a standard nailing schedule calls for 8d common nails every 6 inches. Along the field, a standard schedule calls for 8d common nails every 12 inches.
Fastening Solid Wood Decking
Tongue-and-groove decking planks are among the most common solid wood sheathing products. You must align the ends of planks with rafters or joists and fasten the planks at every rafter or joist that crosses a plank's field. In general, tongue-and-groove decking requires one nail through the tongue edge and one nail through the face at each framing member. Nailing through the tongue-edge -- which is the edge with a protruding strip of wood -- requires driving the nail at an angle, called "toe-nailing." The nail size depends on the plank's thickness. For example, 2-inch-thick decking requires 16d nails.
High-Wind Nailing Schedules
High-wind areas have more complex nailing schedules than areas with normal wind conditions. In high-wind areas, nail schedules are either broken down into zones or increased across the entire roof. For example, roof corners and eave overhangs will have closer spacing than the center of the roof's face. Perimeter nail spacing at the corners can go as low as 3 inches apart. In the areas with the strongest winds, 6 inches is often the shortest spacing between field nails at the center of the roof's face. Consult your local building authority to determine if your project must adhere to a high-wind nailing schedule.
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