July Guideline clarification: nails for enclosed (dry in service) copper-based treated framing

A question has arisen over BRANZ's interpretation of NZS 3604:2011 Table 4.3 and the type of fixings that can be used in dry enclosed situations where the framing is treated with a copper-based treatment.

BRANZ's interpretation in the July Guideline is based on the Build 137 article (page 40) that states, where the timber moisture content remains at 18% or less, bright steel nails can be used with CCA-treated timber and hot-dip galvanised nails used with copper azole and copper quaternary preservative-treated timber.

Note 5 to Table 4.3 in the standard refers to clause 4.4.4, which says that stainless steel fixings are required for copper azole and copper quaternary treated timber in exposed and sheltered locations (part a), while in all other locations (part b), hot-dip galvanising is sufficient. Clause 4.4.4 makes no specific mention of fixing requirements for CCA-treated framing.

Published in building.