Jack rafters – Johnson Level & Tool Mfg. RAS-1 User Manual

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JACK RAFTERS

JACK RAFTER LENGTH: The Jack Rafter Tables are differ-

ent than those for the other rafters. The table lists, in the

first column, the varying center-to-center spacing of the

jack rafters. Then in the second column is the difference in

length from one jack to the next (see Figures 14 and 15).

This difference in length is to be added to or subtracted

from the rafter length as you progress from jack to jack

(using the spacing selected). In our example of a 8" rise,

and lets assume a 24" spacing; we have a 2' 4-7/8" differ-

ence in length. Therefore, to obtain the length of the first

or longest jack rafter, measure the distance from the edge

FIG. 13 Valley Rafter

Layout.