TABLE 1-7. Sizes of Built-up Wood Girders for Various Loads and Spans (Based on Douglas Fir 4-Square Guide-
sides of the girder alternately.
If the girder-
Joists usually carry a uniform load composed of the
supporting pier is to be built up, it is to be done in the
weight of the joists themselves, plus superimposed
same manner as described for the girder.
loads of materials and personnel. The latter loads are
commonly termed "live loads;" the weight of joists
1-31. FLOOR JOISTS
and floors is called "dead load." The joists carry the
flooring directly on their upper surface, and first-
Joists are the pieces which make up the body of
floor joists are supported at their ends by sills and by
the floor frame. The flooring or subflooring is nailed
girders (fig. 1-7). Joists in second and subsequent
to them. They are usually 2 or 3 inches thick and the
floors are supported by bearing partitions, or bearing
depth is varied to suit the conditions. Joists as small
walls. They are spaced 16 or 24 inches apart, center
as 2 x 6 are sometimes used in light buildings, but
to center. If additional strength is necessary, it is
these are too small for floors with spans more than 10
feet though they are frequently used for ceiling joists.