run would give a pitch of 4:12, 6:12, or 8:12. There are two methods of indicating pith.

(1) Method 1. The pitch is indicated as a ratio of the rise to the span of a roof, stated in

fractions (3/4, 5/8, 1/2, and 5/12). The units of span and rise must be the same (inches or feet), and

the faction is reduced to its lowest common denominator (see Figure 3-11, page 3-8).

To obtain the unit rise, multiply the pitch by 24. For example, if the pitch is given as

1/3, multiply 1/3 by 24 (1/3 x 24 = 8). Therefore, the unit rise is 8 inches per foot (8-12

pitch).

If the pitch is given as 5/12, multiply 5/12 by 24 (5/12 x 24 = 10). Therefore, the unit

rise is 10 inches per foot (10-12 pitch).

(2) Method 2. The pitch is stated as the ratio of rise (in inches) per 1 foot of run (12

inches). Using this method, 4, 6, or 8 inches of rise per foot of run would give a pitch of 4-12, 6-12, or

8-12. A roof with 1/2 pitch can be said to have a 12-12 pitch. Remember 1/2 x 24 = 12.

l. Rise. The rise of a rafter is the vertical (or plumb) distance that a rafter extends upward

from the plate.

m. Plumb Line. The line is the line formed by the cord on which the plumb bob is hung (see

Figure 3-28).

n. Plate. The plate is the wall-framing member that rests on the top of the wall studs (see

Figure 3-8, page 3-4).

o. Ridge. The ridge is the highest horizontal roof member. It ties the rafters together at the

upper end (see Figure 3-8).

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