Roof covering material is supported by roof framing. The framing must be strong and rigid. Roof framing consists of several distinct structural elements. The first and most basic of these elements is the rafter. Common rafters are perpendicular to the top of the wall plate. They extend from the plate or beyond to the ridge of the roof. Figure 1-1 shows a plan view of the roof framing for a simple structure. Note that several types of rafters other than common rafters are identified. Rafters are cut to the proper dimensions by locating the ridge cut, the seat cut, the plumb cuts, and the tail cut, Fig 1-2

Roof slope may be given on a drawing by showing a slope ratio diagram or fractional pitch indication. The slope diagram, Fig 1-4 represents the ratio between the rise and run of the roof. The fractional pitch is calculated using the following formula. Pitch=Rise/Run
PDF Roof slope may be also be shown using an angular dimension. However, this method is seldom used because it is difficult to measure as accurately as either of the other methods. A roof with a 45 degree slope has a 12:12 or ? pitch.  There are several common roof pitches used in residential home construction. When designing a roof for your new home, try to use on of the standard roof pitches.