Technical Booklet D Structure·Page 29·4B.10
Floor joists spanning over 2.5 m require strutting
Floor joists spanning more than 2.5 m must be braced with solid or herringbone strutting positioned according to span length. Solid strutting must be at least 38 mm thick and extend 0.75 times the joist depth; herringbone strutting must be 38 mm x 38 mm but only used when joist spacing is not more than 3 times the joist depth.
Floor joists spanning in excess of 2.5 m should be strutted by one or more rows of solid or herringbone strutting in accordance with Table 4B.4. Solid strutting should be at least 38 mm timber thickness extending at least 0.75 times the depth of the joists. Herringbone strutting should be of at least 38 mm x 38 mm timber size but should not be used where the distance between joists is greater than 3 times the depth of the joists.
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