Solution: The side cut of the valley when allowed to rest in the plane of the b 6 / 12 plate = angle B, Fig. (2) Find the side cut of the valley rafter when it rests against the ridge of the minor roof. The numbers just given will give the plumb cut and the seat cut of this valley rafter. Length of valley rafter, then, is found by taking 19.20" on the tongue with 10" (5/6 of 12") on the blade, advancing the setting as many times as there are feet in the run of the common rafter over b. Solution: c2 = a2+b2=(7½)2+62, (a : 12 :: 5 :8, whence a = 7½) c=9.60'Įxpressing this run of valley in terms of 12" of run of common rafter over b. 88-a, in terms of the run of the common rafter over b. (1) Find the run of valley rafter over c, Fig. Minor roof, Rise = 5', Run = 6' = 5/12 pitch. Given: Main roof, Rise = 8', Run = 12' = ⅛ pitch. The following example will make clear the method of attack where it is desired to develop a constant for hip or valley in terms of the common rafter of one of the pitches. The runs for such jacks may be obtained with sufficient accuracy by measurements taken from an accurately made scale drawing. Lengths of cripple jacks will not be of uniform length, as in even pitched roofs. Lengths of hip and valley jacks are determined as in Sec. The amount to be removed from each side must be separately determined according to the angle the hip makes with the plate. The backing of hips on roofs of uneven pitches, while the amount to be removed on each side of the hip will vary, is determined by the principles developed in Sec. Side or cheek cuts for valley, hip or jacks are determined according to principles developed in Sec. Since the angle of intersection changes with every change of pitch, it is hardly worth while developing a constant to be used on the tongue in framing hip and valley rafters on irregular pitches. In selecting the numbers to use on the tongue and the blade of the square, in laying out seat and plumb cuts of hip or valley rafters of intersecting roofs of different pitches, any numbers may be used providing they have a ratio equal to that of the run and rise of the rafter being framed. Lengths of common rafters will be determined for any pitch by the tables already made use of, the run being known or determined. From such a plan it may be seen that the seat and plumb cuts of common and jack rafters are determined in the usual manner, being different upon the different pitches, of course, but determined as for any given pitch. It is advisable to prepare a framing plan as shown in Fig. It remains for the student to make the applications to uneven pitches. All of the principles necessary for framing such a roof have been developed. ![]() Not infrequently a roof must be framed in which several pitches are involved. My differing pitches are 52 and 40 degrees.Framing A Roof Of Uneven Pitch. Perhaps even get a reducing measurement after marking first 2 jacks. Mark 600s off my last full common on the valley rafter, measure each one off the ridge beam, jobs a goodun. Obviously I already know my plum cut angle on jacks. Then can do a scaled sketch or use bevel to figure out angle to cut on jacks. Also done lots on layboards with flat ceilings but obviously a lot easier! So far my plan is to take valleys upto ridge beam- purlin connection using lines to work out my angles. ![]() I've done one in the past and think I just sussed it as I went with lines, levels and bad language. I am also assuming that the valley won't be at 45deg on plan as the steeper roof goes further back into main roof than half its width. ![]() However I can't now use my reckoner to get the angle of the valley for plum and seat cut. The steeper pitched roof is lower than the main roof so the ridge beam connects onto a purlin hung off doubled up attic trusses. Am on a job at the minute with as per title different pitch roofs connecting and vaulted ceiling.
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