A fly rafter is attached to the overhang of your roof. It extends beyond the end of the rafter, if necessary. Fly rafters help keep the plywood or other type of roof sheathing straight. The size of a fly rafter can vary depending on personal preference, but should be slightly smaller then the regular roof rafters. It can range from 2-by-8 inches to 2-by-10. Installing fly rafter boards is similar to installing any other rafter and they are beneficial when your roof has an overhang.
Things You'll Need
Measure the size of your roof rafters and determine how big the fly rafters need to be. If the roof rafters are 2-by-10 inches, then the fly rafters will be 2-by-8; if the roof rafters are 2-by-8 then the fly rafters will be 2-by-6.
Determine the height of the gable overhang and cut fly rafters to size based on the height. Two rafters will be needed to form the overhang. Add 3/4 of an inch to each of the cuts to make up for the missing ridge.
Measure and mark the rafters at the proper cut location and slide them into a miter saw. Push them up against the fence of the saw and line up the blade with the mark on the saw. Pull down on the lever and cut them to the proper size.
Line the two rafters up on the ground nine inches apart and cut small pieces to connect the two so it will look like a ladder. Set the nine-inch pieces between the rafters and hammer them in place to each rafter with roofing nails. Move down 24 inches and repeat the process all the way down the rafters. It will look like a ladder when you are complete.
Carry the rafter up to the overhang and nail it in place horizontally to the gable end of the roof. Hammer in roofing nails every eight inches to secure it. Repeat the process for the fly rafter on the other side of the gable.
Always wear safety goggles when you are working with a miter saw. This will help protect your eyes from bits of flying wood and other debris.