(4) Follow the Length Per Foot Run common rafters row across to the right until you are in the column under the number that corresponds with the pitch desired. The number in the intersecting box is your other working number. Remember that number.(Notice that this number has a decimal)
For this Instructable I am making an 8/12 rafter, If you do not have a framing square with the "Common Rafters Per Foot Run" table on it, the numbers for the various roof pitches are as follows. . . . .
(2/12 pitch=12.17) (3/12 pitch=12.37) (4/12 pitch=12.65) (5/12 pitch=13.00) (6/12 pitch= 13.42)
(7/12 pitch=13.89) (8/12 pitch=14.42) (9/12 pitch=15.00) (10/12 pitch=15.62) (11/12pitch=16.28)
(12/12pitch=16.97) (13/12pitch=17.69) (14/12 pitch=18.44) (15/12 pitch=19.21) (16/12 pitch=20.00)
(17/12 pitch=20.81) (18/12 pitch=21.63)