![]() Since the pitch of the addition roof is the same as the pitch of the main roof, equal spans bring the ridge pieces to equal heights. Figure 2-38 shows an equal-span framing situation, in which the span of the addition is the same as the span of the main roof. In an equal-pitch roof, the valley rafters always run at 45° to the building lines and the ridge pieces. Also, the unit of run and unit of rise of an addition or dormer common rafter are assumed to be the same as the unit of run and rise of a main-roof common rafter. In the discussion of valley rafter layout, it is assumed that the roof is equal pitch. ![]() There are unequal-pitch valley-rafter methods. Most roofs having valley rafters are equal-pitch roofs, in which the pitch of the addition or dormer roof is the same as the pitch of the main roof. A valley rafter follows the line of intersection between a main-roof surface and a gable-roof addition or a gable-roof dormer surface. Consequently, they are the same length as the hip rafters. This places them parallel 10 the hip rafters. Valley Rafters Valley rafters run at a 45° angle to the outside walls of the building. Note that the ridgeboard is lower on the section with the shorter span. In addition, a valley cripple jack rafter is placed between the supporting and shortened valley rafters. ![]() Like an intersecting roof with equal spans, one with unequal spans also requires valley jack rafters and hip-valley cripple jack rafters. A shortened valley rafter runs from the other inside comer of the building to the supporting valley rafter. An intersecting roof with unequal spans requires a supporting valley rafter to run from the inside corner formed by the two sections of the building to the main ridge (fig. Hip-valley cripple jack rafters are placed between the valley and hip rafters. Valley jack rafters run roofs, but they are quite rare and require special framing from the valley rafters to both ridges. Figure 2-37.Intersecting roof with unequal spans. ![]()
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