To find the line length of a rafter with a total run of 10 feet 4 inches, multiply 17.69
inches by 10 1/3 and divide by 12 to get the answer in feet (17.69 x 10.333 = 182.79).
The total of 182.79 inches is divided by 12 to equal 15 3/12 feet. Therefore, 15 feet 3
inches is the line length of the rafter.
(5) Table Method 2. The rafter table is on the back of the blade of some squares. Figure 3-
13 shows the run, rise, and pitch of the rafters of the seven most common roof pitches. The figures are
based on the length of the horizontal measurement of the building from the center to the outside (run).
The rafter table on the outside edge, on the back of the square, gives both the body and the tongue in
twelfths. The inch marks on the square may represent inches or feet, and the twelfth marks may
represent twelfths of an inch or twelfths of a foot. The rafter table is used in connection with the marks
and figures on the outside edge of the square. You will notice that at the left end of the table there are
figures representing the run, rise, and the pitch.
Figure 3-13. Table Method 2
Run. In the first column, the figures are all 12. These may be used as 12 inches or
12 feet, because they represent the run of 12 inches.
Rise. The second column of figure represents various rises per foot: 4, 6, 8, 10, 12,
15, and 18.
Pitch. The third column of figures, in fractions, represents various pitches: 1/6, 1/4,
1/3, 5/12, 1/2, 5/8, and 3/4 (see Figure 3-14, page 3-10).
3-9
EN5156
Previous Page
