Finding the backing angle of the hip on a regular roof with a framing square

A regular roof is one in which the hips or valleys meet at 90 degrees.

Example: Find the backing angle on a hip rafter with 8:12 roof? The hip is 4” wide.

1. Using a framing square hold 8” on the tongue and 17” on the body. This will give you the plumb and level cuts on the hip.
2. Draw a level line 2” long on the hip. (1/2 the thickness of the hip material)
3. Draw a line parallel to the top of the hip to the end of the timber.
4. On the end of the timber connect the line (step 3) to the center line of the hip.

This is the backing angle of the hip. It is also the bevel angle for the saw.

View the PDF to see a drawing of this. Backing Angle