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Fixing stringers

It is common for timber decks to be supported on a stringer bolted to the adjacent building structure. NZS 3604:2011 Timber-framed buildings requires M12 bolts spaced in accordance with Table 6.5. Bolts must be fixed through solid framing.

A second question is whether coach screws can be used. BRANZ engineers advise that they can, provided:

  • the fixings are at 600 mm centres
  • penetration into framing is at least 85 mm
  • the pilot hole diameter is the same as the root diameter of the screw.

All fixings will need to meet the durability requirements of NZS 3604:2011 section 4.

Summarised from BRANZ Guideline, February 2015.