Figure 2-53.—Jack rafter framing diagram.
The best way to figure the total runs of valley jacks
and cripple jacks is to lay out a framing diagram and
study it to determine what these runs must be. Figure
2-53 shows part of a framing diagram for a main hip roof
with a long and short valley rafter gable addition. By
studying the diagram, you can figure the total runs of
the valley jacks and cripple jacks as follows:
The run of valley jack No. 1 is obviously the same
as the run of hip jack No. 8, which is the run of
the shortest hip jack. The length of valley jack
No. 1 is therefore equal to the common difference
of jacks.
The run of valley jack No. 2 is the same as the
run of hip jack No. 7, and the length is therefore
twice the common difference of jacks.
The run of valley jack No. 3 is the same as the
run of hip jack No. 6, and the length is therefore
three times the common difference of jacks.
The run of hip-valley cripple Nos. 4 and 5 is the
same as the run of valley jack No. 3.
Figure 2-54.-Line and actual lengths of hip roof ridgeboard.
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