Intersecting

Figure 2-35.-Backing or dropping a hip rafter. the top edge of the hip rafters. Dropping means to deepen the bird’s-mouth so as to bring the top edge of the hip rafter down to the upper ends of the jacks. The amount of drop is taken on the heel plumb line (fig. 2-34, view D). The backing or drop required is calculated, as shown in figure 2-34, view B. Set the framing square to the cut of the rafter (8 inches and 17 inches) on the upper edge, and measure off one-half the thickness of the rafter from the edge along the blade. A line drawn through this mark and parallel to the edge (view C) indicates the bevel angle if the rafter is to be backed. The perpendicular distance between the line and the edge of the rafter is the amount of the drop. This represents the amount the depth of the hip rafter bird’s-mouth should exceed the depth of (view D). INTERSECTING the common rafter bird’s-mouth An intersecting roof, also known as a combination roof, consists of two or more sections sloping in different directions. A valley is formed where the different sections come together. The two sections of an intersecting roof mayor may not be the same width. If they are the same width, the roof is said to have equal spans. If they are not the same width, the roof is said to have unequal spans. Spans In a roof with equal spans, the height (total rise) is the same for both ridges (fig. 2-36). That is, both sections are the same width, and the ridgeboards are the same height. A pair of valley rafters is placed where the slopes of the roof meet to form a valley between the two sections. These rafters go from the inside corners formed by the two sections of the building to the corners Figure 2-36.-Intersecting roof with equal spans. 2-25