The number of nails needed for a roof varies on multiple factors, such as board face width, length and roof truss spacing. Boards used for sheathing range from those with a 4-inch face to 48-inch-long plywood sheets. A structure's roof truss spacing can vary from every 12 to 24 inches. Each of these factors plays a role in determining how many nails you'll need to use per board during roof sheathing application. Boards require a minimum of two nails per truss, while sheathing requires six nails due to face width and nail spacing.
The type of nails you'll need to use during the sheathing process depends on the roof material thickness. You should use 3-inch ring shank nails to allow at least 1 1/2 inches of truss penetration when working with lumber slats. You can use 2-inch galvanized nails when working with plywood or oriented strand board (OSB) sheets, which measure 4 feet by 8 feet.
Roof Truss Spacing
Roof truss spacing will vary on the structure's construction. There are typically 12-, 16- or 24-inch spans between each roof truss. You'll need to use nails wherever the roof sheathing makes direct contact with each truss. The number of nails you'll need depends on the face width of the sheathing you're using. Slats will require more courses and more nails, while large sheets of plywood or OSB will require fewer since you can space nails farther apart when working with the material.
Slats of wood used for roof sheathing are lumber boards with face widths ranging from 4 to 12 inches. Generally, you'll need to place two nails at each location where it makes contact with a roof truss. For slats featuring face widths of 12 inches, you will space three nails evenly apart about every 3 inches. A typical slat length can run from 12 to 16 feet. Slats were commonly used in early home construction but are not used much today. Now larger sheets of plywood, or OSB, are available at a cheaper cost.
Nail spacing for sheets of OSB and plywood is 8 inches per nail. This means that you'll need to use six nails per each truss that runs under the sheathing because each sheet measures 4 feet wide by 8 feet long; 4 feet equals 48 inches, which you then divide by 8 to determine that you'll need six nails where the board comes in contact with a truss. A truss spacing of 16 inches means that there are six trusses underneath the sheathing, so you'll use a total of 36 nails (six times six) per sheet. This number will vary if the trusses are spaced differently.