AS 1720.5:2015 Australian Standard Timber structures
3.4.5.1 Top chords
The fixing of battens to every ply of truss top chords with screws or nails in conjunction with diagonal bracing shall be deemed to provide lateral restraint. For hip trusses and girder trusses, the fixing of supported trusses to the chords shall also be deemed to provide lateral restraint to the chords in addition to the battens. The spacing of batten restraints on hip trusses shall take into account the angle the battens make with the truss. Timber roof battens butt spliced over a truss shall be disregarded from providing lateral restraint unless specific splicing details that deliver restraint are provided. For concrete tile roofs, every second roof batten shall be regarded as an ineffective lateral restraint.
NOTES:
1 For top hat metal battens to be effective in providing lateral restraint, they should be fastened at their base feet to every ply of truss chord.
2 Top hat metal batten profiles screwed to top chords only through the crest of the batten are not deemed to provide adequate lateral restraint.
3 Where required, splices in battens or purlins should be arranged such that in any top chord no more than one-third of battens or purlins are spliced and no two splices are adjacent. There should be no splices in battens or purlins over girder trusses.
4 For light roofs (e.g sheet metal), all roof batten splices should employ specific details to render them effective for lateral restraint against the top chord.
5 Top hat metal battens simultaneously fixed at their base feet through overlapping splices are generally assumed to provide adequate continuity.
6 Where the further design methods for members given in AS 1720.1 are used to assess forces on lateral restraints, n should be taken as the number of equally spaced restraints over the entire length of a straight chord (including splices) between pitch changes and not just the length of a single panel between joints. In typical circumstances, n is the chord length divided by the batten spacing, rounded down to the nearest integer.