Placing Floor Joists

Figure 1-27.—Metal cross bridging. tops of the bridging. Instep 3, reverse direction and nail tops of the opposite pieces into place. Another approved system of cross bridging uses metal pieces instead of wood and requires no nails. The pieces are available for 12-, 16-, and 24-inch joist spacing (fig. 1-27, view A). You can see how to install this type of cross bridging in views B, C, and D. In view B, strike the flat end of the lower flange, driving the flange close to the top of the joist. In view C, push the lower end of the bridging against the opposite joist. In view D, drive the lower flange into the joist. SOLID BRIDGING.— Also known as solid blocking, solid bridging (fig. 1-28) serves the same purpose as cross bridging. This method is preferred by many Builders to cross bridging. The pieces are cut from lumber the same width as the joist material. They can be installed in a straight line by toenailing or staggering. If staggered the blocks can be nailed from both ends, resulting in a faster nailing operation. Straight lines of blocking may be required every 4 feet OC to provide a nailing base for a plywood subfloor. Placing Floor Joists Before floor joists are placed, the sill plates and girders must be marked to show where the joists are to Figure 1-28.—Solid bridging. be nailed. As we mentioned earlier, floor joists are usually placed 16 inches OC. For joists resting directly on foundation walls, layout marks may be placed on the sill plates or the header joists. Lines must also be marked on top of the girders or walls over which the joists lap. If framed walls are below the floor unit, the joists are laid out on top of the double plate. The floor layout should also show where any joists are to be doubled. Double joists are required where partitions resting on the floor run in the same direction as the floor joists. Floor openings for stairwells must also be marked. 1-13