Figure 2-32.—Run of hip rafter projection.18 inches for a roof with an 8-inch unit of rise, the lengthof the hip or valley rafter tail is figured as follows:1.2.Find the bridge measure of the hip or valleyrafter on the framing square (refer to figure2-16). For this roof, it is 18.76 inches.Multiply the bridge measure (in inches) of thehip or valley rafter by the projection (in feet) ofthe common rafter overhang:3. Add this product to the theoretical rafter length.The overhang may also be stepped off as describedearlier for a common rafter. When stepping off thelength of the overhang, set the 17-inch mark on the bladeof the square even with the edge of the rafter. Set theunit of rise, whatever it might be, on the tongue evenwith the same rafter edge.Rafter Side CutsSince a common rafter runs at 90° to the ridge, theridge end of a common rafter is cut square, or at 90° tothe lengthwise line of the rafter. A hip rafter, however,joins the ridge, or the ridge ends of the common rafter,at other than a 90° angle, and the ridge end of a hip raftermust therefore be cut to a corresponding angle, called aside cut. The angle of the side cut is more acute for ahigh rise than it is for a low one.The angle of the side cut is laid out as shown infigure 2-33. Place the tongue of the framing squarealongFigure 2-33.—Laying out hip rafter side cut.the ridge cut line, as shown, and measure offone-half the thickness of the hip rafter along the blade.Shift the tongue to the mark, set the square to the cut ofthe rafter (17 inches and 8 inches), and draw the plumbline marked “A” in the figure. Then, turn the rafteredge-up, draw an edge centerline, and draw in the angleof the side cut, as indicated in the lower view of figure2-33. For a hip rafter to be framed against the ridge, therewill be only a single side cut, as indicated by the dottedline in the figure. For one to be framed against the ridgeends of the common rafters, there will be a double sidecut, as shown in the figure. The tail of the rafter musthave a double side cut at the same angle, but in thereverse direction.The angle of the side cut on a hip rafter may also belaid out by referring to the unit length rafter table on theframing square. (Look ahead to figure 2-41.) You willsee that the bottom line in the table is headed SIDE CUTHIP OR VALLEY USE. If you follow this line over tothe column headed by the figure 8 (for a unit of rise of8), you will find the figure 10 7/8. If you place theframing square faceup on the rafter edge with the tongueon the ridge-end cut line, and set the square to a cut of10 7/8 inches on the blade and 12 inches on the tongue,you can draw the correct side-cut angle along thetongue.2-23
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