Figure 2-48.—Method of framing gable dormer with sidewalls.
method of framing, the shortening allowance for the
upper end of a valley rafter is one-half the 45° thickness
of the inside member in the upper doubled header. There
is also a shortening allowance for the lower end,
consisting of one-half the 45° thickness of the inside
member of the doubled common rafter. The figure also
shows that each valley rafter has a double side cut at the
upper and lower ends.
Figure 2-48 shows a method of framing a gable
dormer with sidewalls. As indicated in the framing
diagram, the total run of a valley rafter is again the
hypotenuse of a right triangle with the shorter sides each
equal to the run of a common rafter in the dormer. You
figure the lengths of the dormer corner posts and side
studs just as you do the lengths of gable-end studs, and
you lay off the lower end cutoff angle by setting the
square to the cut of the main roof.
Figure 2-49 shows the valley rafter shortening
allowance for this method of framing a dormer with
sidewalls.
Figure 2-49.-Valley rafter shortening allowance for dormers
with sidewalls.
Figure 2-50.-Types of jack rafters.
Jack Rafters
A jack rafter is a part of a common rafter, shortened
for framing a hip rafter, a valley rafter, or both. This
means that, in an equal-pitch framing situation, the unit
of rise of a jack rafter is always the same as the unit of
rise of a common rafter. Figure 2-50 shows various types
of jack rafters.
A hip jack rafter extends from the top plate to a hip
rafter. A vane y jack rafter extends from a valley rafter
to a ridge. (Both are shown in fig. 2-51.) A cripple jack
rafter does not contact either a top plate or a ridge. A
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