254 Section 2 Foundations and Framing The type shown in Figure 10-36 is manufactured from sheet steel. A V-shaped cross section makes it rigid. No nails are required and it is driven into place with a regular hammer. After the bridging is installed, the floor frame should be carefully checked to see that nailing patterns have been completed in all members. After this is done, the frame is ready to receive the subflooring. Subflooring is a covering of boards or panels, nailed to the joists, over which a finish floor is laid. Procedure Installing Wood Bridging 1. Snap a chalk line across the tops of the joists at the center of their span. 2. Use two 8d nails to attach the top of the bridging to each side of every joist. Alternate the positioning of the bridging, first on one side of the chalk line and then on the other. 3. After the subflooring is complete or before the under surfaces of the floor are enclosed, the lower ends of the bridging are nailed to the joist. 10.5 Special Framing Problems A building’s design may include a section of floor that overhangs a lower floor or basement level. When the floor joists run at right angles to the walls, use longer joists, Figure 10-37. If the run of joists is parallel to the supporting wall, extend cantilevered joists inward two to three times the length of the overhang, Figure 10-38. The exact spacing between joists and length of the members depends on the weight of the outside wall. This information is covered in IRC Section R502.3.3. Entrance halls, bathrooms, and other areas are often finished with tile or stone that is installed on a concrete base. To provide room for this base, the floor frame must be lowered. When the area is not large, 9 1/4" 2 x 10 joist 16" O.C. 14 1/2" Goodheart-Willcox Publisher Figure 10-35. A carpenter’s framing square can be used to lay out bridging. The line for the lower cut can be found by shifting the tongue of the square to the 14 1/2″ mark on the stock. A B Timber Engineering Co. Figure 10-36. Using steel bridging. A—One type of steel bridging. B—Installation method. Copyright Goodheart-Willcox Co., Inc.