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Timber treatment
By Trevor Pringle, ANZIA, BRANZ Principal Writer, February 2012.
Download Build128_Pg19_BuildRight_TimberTreatment (pdf)
Executive summary
The treatment requirements for timber framing were changed in 2011, so it’s a good time to recap the required levels of treatment for different timber members.
In April 2011, B2/AS1 Amendment 7 introduced new tables for radiata pine and Douglas fir to replace those in NZS 3602:2003, an Acceptable Solution for choosing timber and wood-based products for use in buildings. H3.1 LOSP treatment was no longer permitted for framing timber. H1.2 boric treatment became the minimum requirement for radiata pine and Douglas fir framing timbers – the exception being H3.2 treatment for cantilevered floor joists and associated framing (see Table 1). Amendment 7 also allows the use of untreated Douglas fir framing within clearly defined building design parameters.
Use of any other framing timber or treatment must be submitted for consent, together with supporting information to show the timber will be sufficiently durable as framing, as an alternative method. Naturally durable timbers are seldom used for timber framing, but western red cedar or redwood can be used untreated for finishing, exterior joinery and claddings (see the BRANZ book Selecting timber).
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