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Installing Cross Bridging Or Blocking
Cross bridging or
blocking must
be installed to keep the joists
from twisting. The distance between rows of cross-bridging or
blocking must not exceed 2.1 metres (7 feet). The distance
from
the ends of joists to cross-bridging or blocking must not exceed 2.1
metres (7 feet).Figure 25 shows you how the framing square is used to lay out the cross-bridging for cutting.
Use a framing square to lay out cross bridging. Determine the distance between floor joists and the joist's height. Assume a 38 by 235 mm (1.5 inches by 9.25 inches) floor joist at 400 mm (16 inches) on centre. Its height will be 235 mm (9.25 inches) reduced to 225 mm (8.86 inches) because of joist shrinkage and the distance between floor joists will be 362 mm (14.5 inches).
To install cross bridging, snap a chalk line across the joists. Nail two 57mm (2.25 inches) nails to each end of the cross-bridging before nailing it to the top of the joist. The bottom nails are nailed when the sub floor has been laid and the joist shrinkage is complete.
