The importance of users selecting the right fastener type for the type of treated wood being used has been highlighted in a new Technical Note.
Over recent years, there has been an increase in the use of alternative treatment chemicals in the New Zealand timber market. Whilst these products are understood to be treated to appropriate Hazard Classes in accordance with NZS 3640 and/or AS/NZS 1604:2012 Series as Acceptable Solutions (and/or Codemark) under the New Zealand Building Code (NZBC), the effect of the chemicals used in these treatments on fasteners, must also be considered.
Koppers Performance Chemicals (Koppers), the pre-eminent supplier of timber treatment chemicals to the New Zealand timber market, has put together a Technical Note, ‘Fasteners for Treated Timber’. In this Technical Note, available for download below, Koppers confirms that MCA treatments of timber, plywood and other wood-based products will require fasteners to be Grade 304 Stainless for all Sheltered and Exposed positions in all exposure Zones in accordance with NZS 3604.
Further, this Technical Note clarifies that NZS 3604 states, "Wood treated with Copper Azole (CuAz) or ACQ is expected to be more corrosive and will require fasteners to be a minimum of Type 304 stainless steel when used in Sheltered or Exposed situations. Micronized Copper Azole (known in market by its acronym, MCA) is by the current definition a Copper Azole preservative and therefore requires stainless steel fasteners in accordance with NZS 3604, part of the NZBC Acceptable Solution for Durability, B2/AS1.”
When asked about the effects of corrosion on fasteners, Koppers advised, “New Zealand building standards have some unique requirements for long-term fastener performance, and it is important that users select the right fastener type for the type of treated wood being used.
Cameron Rodger, Technical Director for the Carter Holt Harvey Group, summed this up by noting, “With alternative treatments becoming more readily available, this information illustrates the importance of using suitable fasteners for the type of treatment, given the consequences of not complying to New Zealand building regulations.”
