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.