Figure 1-60.—Ceiling frame tying exterior walls together.JOISTSJoists are the most important framing members ofthe ceiling. Their size, spacing, and direction of travelare given on the floor plan. As mentioned earlier, thespacing between ceiling joists is usually 16 inches OC,although 24-inch spacing is also used. The size of aceiling joist is determined by the weight it carries andthe span it covers from wall to wall. Refer to theblueprints and specifications for size and OC spacing.Although it is more convenient to have all the joistsrunning in the same direction, plans sometimes call fordifferent sets of joists running at right angles to eachother.Interior SupportOne end of a ceiling joist rests on an outside wall.The other end often overlaps an interior bearing partitionor girder. The overlap should be at least 4 inches. Ceilingjoists are sometimes butted over the partition or girder.In this case, the joists must be cleated with a3/4-inch-thick plywood board, 24 inches long, or an18-gauge metal strap, 18 inches long.Ceiling joists may also butt against the girder,supported by joist hangers in the same manner as floorjoists.Roof RaftersWhenever possible, the ceiling joists should run inthe same direction as the roof rafters. Nailing the outsideend of each ceiling joist to the heel of the rafter as wellas to the wall plates (fig. 1-61) strengthens the tiebetween the outside walls of the building.A building maybe designed so that the ceiling joistsdo not run parallel to the roof rafters. The rafters aretherefore pushing out on walls not tied together byceiling joists. In this case, 2 by 4 pieces are added to runFigure 1-61.—Nailing of ceiling joists.1-35
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