How to Put Roof Decking on a Ranch Home

Calculate the amount of decking material you'll need for the roof. Measure the width and height of one side of the roof. Multiply these numbers by each other to find the area of one side of the roof, then multiply the area by two to find the total area of the roof. Increase the total area of the roof by 15 percent to account for material that may be wasted on mistakes. To calculate 15 percent, take the total area and multiply it by 0.15. Purchase the total amount of decking that you have just determined you will need.

Pick a side to start working on. Lay the first panel of decking over the lower left-hand corner of the roof. Plywood comes in sheets of 8 feet by 4 feet. Situate the panel horizontally, so that it is wider than it is tall. Position the left edge of the panel so it is flush with the gable on the left. Place the bottom edge of the panel so it is in line with the bottom edge of the roof rafter. The right side of the decking should line up with the center of a rafter. If it does not, mark the panel where it falls over the center of the closest rafter and cut the panel with a circular saw.

Nail down the decking to the rafters with roofing nails positioned every 6 inches on the outer edges of the panel and every 12 inches throughout the center of the panel. The nails should penetrate the panel and go directly into the rafters. Use a roofing nail gun and roofing nails to make this part go more quickly.

Lay down the next panel in the course to the right of the first panel. Leave a 1/8-inch gap between the first panel and this second panel to accommodate expansion in times of high moisture. Line up the second panel so that the right and left edges fall directly over a rafter. The rafters should be installed at distances to make this possible. If not, you may need to cut the plywood with a circular saw. Nail down the second panel of decking to the right of the first panel, using the same procedure that you used to nail down the first panel.

Continue to nail down sheets of plywood across the first course until you have reached the other side of the roof. Cut the last piece of plywood to fit with a circular saw if a whole sheet of plywood will not fit.

Cut the first panel of the second course in half, using a circular saw. This will give you a piece of 4-by-4 foot plywood. By starting the second course with a half-sized piece of plywood, you will stagger the placement of the panels in the second course over the panels in the first course, much like bricks on a wall. To continue this pattern, alternate the size of the first piece of plywood that you use in each course. The third course will start with a full-sized sheet, the fourth with a half-sized sheet, and so on.

Nail down the second course of plywood in the same way that you nailed down the first course. Leave a 1/8 inch gap between all pieces of plywood. This should include a space between the first course and second course. Continue to nail down plywood until you've reached the top of the roof. You may need to cut the final course to fit in the space left at the top of the roof.

Repeat Steps 2 through 7 on the other side of the roof.