Laying out hip, valley, and jack rafters takes experience and skill, but if you’re building a simple gable or shed roof, all you need is the common rafter, the basic building block of roof framing.
To lay out a common rafter, you need the pitch of the roof, expressed in units of rise per foot of run. In the gable-roof example shown here, a rafter with 6-in-12 pitch rises 6 in. for every foot of run. Run is the horizontal distance that the rafter covers. For a gable roof, the run is measured from the centerline of the ridge board to the outside edge of the top of the wall.