When Tables 4.1 and 4.3 in NZS 3604:2011 Timber-framed buildings are being read, there is often confusion over when clause 4.4.4 applies.
To clarify, clause 4.4.4 only applies where copper azole (preservative code numbers 58 for copper azole and 88 for micronised copper azole) or copper quaternary (preservative code numbers 90 for copper quaternary and 89 for micronised copper quaternary) are used. The use of these treatments will require the upgrading of fasteners as outlined in clause 4.4.4 – typically to 316 stainless steel.
If the timber is copper chrome arsenate-treated (CCA preservative code numbers 01 and 02), use Tables 4.1 and 4.3 – clause 4.4.4 does not apply to CCA-treated timber.
Summarised from BRANZ Guideline magazine, October 2013.