Fig. 60. - Obtaining: Bevel Across the Back of Jack Rafters.
Let us now consider the backing of the hip rafter, an item which on common house and barn framing is of but little importance, yet it is well enough to know how it is done. Almost any roof is as good without as with the hips backed, and when the roof is completed it is impossible to tell which method was pursued. In cases where the hip rafter is doubled or very thick it is advisable to back it, but ordinarily this is unnecessary, being a waste of time. Where backing is necessary, a rule near enough for all practical purposes is as follows: Working from the center of the back of rafter set the bevel to cut off ⅝ inch in 1 inch for three-fourth pitch roofs. ½ inch in 1 inch for one-half pitch roofs. ⅜ inch in 1 inch for one-third pitch roofs. ½ inch in 1 inch for one-quarter pitch roofs.
Fig. 61. - Backing a Hip Rafter.
As the above table may not be considered a scientific way of doing the work, Fig. 61 is presented. Draw a horizontal line, A B, and from A draw another at an angle representing the bottom cut of the hip rafter, as A C. On the line A C square up the thickness of the rafter to D. Mark the center and draw the line C F at an angle of 450 to A D. On the line E F square up from E to G, and the lines for the backing are G E F. The other lines are merely to show that the piece is off the bottom end of the hip rafter itself.