The load per linear foot on the girder.
The total load on the girder.
The material to be used.
1-4. Depth. When the depth of a girder is doubled, the safe load is increased four times. For
example, a girder that is 3 inches wide and 12 inches deep will carry four times as much weight as a
girder 3 inches wide and 6 inches deep. To obtain greater carrying capacity, it is better to increase the
depth than to increase the width of the girder. The sizes of built-up wood girders for various loads and
spans may be determined by using Table 1-1.
Table 1-1. Sizes of built-up wood girders