Tips

Topic: Roof Framing.

Plywood Cut.

On of the interesting aspects of cutting hip roofs is laying the sheathing down. Even though the hip forms a 45° with the corner of the roof, the plywood isn't cut at a 45°. The angle to cut the sheet of plywood at is equal to the side cut of the jack rafters.

To calculate the plywood cut for any regular hip roof simply divide the base run of 12 by the unit length for the pitch used and preform the ArcTangent function on the quotient. If you were working with a 9/12 roof it would be Tan^-1(15/12) = 51.34° where 15 is the unit length of a 9/12 common rafter.

You can then place the 12 on the tongue at the corner of the sheet of plywood and 15 on the body at the edge and mark the tongue to produce the correct angle for the cut.