Change to Acceptable Solution for timber preservative treatment
MBIE has published an amendment to Acceptable Solution B2/AS1 for timber durability. This guidance looks at the latest amendment.
The information was confirmed as current in November 2017. It originally appeared in Codewords 60.
B2 /AS1 amendment 8 references the following three Standards together with modifications as noted below:
- NZS 3640:2003 Chemical Preservation of Round and Sawn Timber, adding amendments 4 and 5
- NZS 3602:2003 Timber and Wood-based Products for use in Building
- NZS 3604:2011 Timber-framed buildings
B2/AS1 amendment 8 took effect from 14 February 2014, and B2/AS1 amendment 7 was effective until 14 August 2014.
Acceptable Solutions and Verification Methods for Building Code Clause B2 Durability has more information.
Modifications relating to citation of NZS 3640, NZS 3602, and NZS 3604 are:
NZS 3640
B2/AS1 amendment 8 includes the following two modifications to NZS 3640:
- Comment clause C3.1 is cited as normative text.
- Clause 6.3.1.1.1 is reinstated as “Complete sapwood penetration shall be achieved”.
NZS 3602
Modifications to the previous citation of NZS 3602, in B2/AS1 amendment 7, remain unaltered. This latest citation of B2/AS1 includes a special provision for treated LVL framing with the inclusion: Laminated Veneer Lumber (LVL) treated using LOSP borne azoles as specified for H3.1 in NZS 3640 Table 6.2 satisfies the minimum treatment requirement of H1.2.
NZS 3604
References to NZS 3604, as modified by references to NZS 3640 and NZS 3602 noted above.