• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Valley Rafters
Figure 2-41.-Rafter table method.

Builder 3&2 Volume 02 - Construction manual for building structures
Page Navigation
  62    63    64    65    66  67  68    69    70    71    72  
Figure 2-38.-Equal-span intersecting roof. Figure 2-40.-Equal pitch but unequal span framing. Figure 2-39.-Ridge-end shortening allowance for equal-span intersecting valley rafter. hip  rafter.  The  valley-rafter  tail  has  a  double  side  cut (like the hip-rafter tail) but in the reverse direction. This is because the tail cut on a valley rafter must form an inside, rather than an outside, corner. As indicated in figure 2-39, the ridge-end shortening allowance in this framing  situation  amounts  to  one-half  of  the  45° thickness  of  the  ridge. Figure 2-40 shows a framing situation in which the span of the addition is shorter than the span of the main roof. Since the pitch of the addition roof is the same as the  pitch  of  the  main  roof,  the  shorter  span  of  the addition brings the addition ridge down to a lower level than that of the main-roof ridge. There are two ways of framing an intersection of this type. In the method shown in figure 2-40, a full- length valley rafter (AD in the figure) is framed between the  top  plate  and  the  main-roof  ridgeboard.  A  shorter valley rafter (BC in the figure) is then framed to the longer one. If you study the framing diagram, you can see that the total run of the longer valley rafter is the hypotenuse of a right triangle with the altitude and base equal to the total run of a common rafter in the main roof. The total run of the shorter valley rafter, on the other hand, is the hypotenuse of a right triangle with the altitude and base equal to the total run of a common rafter in the addition. The total run of a common rafter in the main roof is equal to one-half the span of the main roof. The total run of a common rafter in the addition is equal to one-half the span of the addition. Knowing the total run of a valley rafter, or of any rafter for that matter, you can always find the line length by applying the bridge measure times the total run. 2-27







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.