Selecting deck joists from NZS 3604
Deck joists selected from NZS 3604:2011 Timber-framed buildings Table 7.1b (wet in service) require lateral support at mid span when they span more than 2.5 metres and have a depth of four or more times their thickness (clause 220.127.116.11).
Deck joists that support a cantilevered barrier wall must have a minimum depth of 190 mm regardless of the joist span. (A cantilevered barrier is one that has attachment to the deck joists at the base of the barrier.)
Where deck joists are cantilevered, they require lateral support (solid blocking) between the joists along the line of the cantilever support wall or bearer.
- Read more on cantilevered joists for decks(external link)
Summarised from BRANZ Guideline December 2013