Figure 1-60.—Ceiling frame tying exterior walls together.
JOISTS
Joists are the most important framing members of
the ceiling. Their size, spacing, and direction of travel
are given on the floor plan. As mentioned earlier, the
spacing between ceiling joists is usually 16 inches OC,
although 24-inch spacing is also used. The size of a
ceiling joist is determined by the weight it carries and
the span it covers from wall to wall. Refer to the
blueprints and specifications for size and OC spacing.
Although it is more convenient to have all the joists
running in the same direction, plans sometimes call for
different sets of joists running at right angles to each
other.
Interior Support
One end of a ceiling joist rests on an outside wall.
The other end often overlaps an interior bearing partition
or girder. The overlap should be at least 4 inches. Ceiling
joists are sometimes butted over the partition or girder.
In this case, the joists must be cleated with a
3/4-inch-thick plywood board, 24 inches long, or an
18-gauge metal strap, 18 inches long.
Ceiling joists may also butt against the girder,
supported by joist hangers in the same manner as floor
joists.
Roof Rafters
Whenever possible, the ceiling joists should run in
the same direction as the roof rafters. Nailing the outside
end of each ceiling joist to the heel of the rafter as well
as to the wall plates (fig. 1-61) strengthens the tie
between the outside walls of the building.
A building maybe designed so that the ceiling joists
do not run parallel to the roof rafters. The rafters are
therefore pushing out on walls not tied together by
ceiling joists. In this case, 2 by 4 pieces are added to run
Figure 1-61.—Nailing of ceiling joists.
1-35
