This guidance looks at an alternative solution for treated framing to ensure ongoing identification on the timber.
The information was confirmed as current in November 2017. It originally appeared in Codewords 63.
Pink-coloured framing is almost universal throughout building projects these days.
‘Pink” has been the identifying colour for boron-treated framing since its introduction in the early 1950s.
A disadvantage with this treatment identification branding is that the pink colouring fades over time and end brand markers are removed during construction. This results in loss of ongoing identification on the timber for treatment type, Hazard class, etc. (colour fading does not affect the treatment level).
More permanent treatment marking, such as continuous branding down the length of the timber (in the same way as timber stress grading) is considered a more reliable branding option for treatment. However, most timber suppliers claim this is incompatible with production processes and adds cost to the timber to brand in this way.
The treatment Standard NZS 3640 Chemical Preservation of Round and Sawn Timber provides a continuous branding option for those suppliers wanting to use it. Table 5.1 states that timber framing can be branded either by:
- one end of each piece, or
- repetitively along the length at 1.5m centres.
Irrespective of the branding option above, the Standard also requires certain timber framing to be coloured (pink in the case of H1.2 boron) with a colour-fast rating of 5 in accordance with BS ISO 12040. However, experience has shown that transparent colouring (dye or pigment) cannot be made permanent.
If continuous branding is in permanent ink, or imprint stamp, it is not logical that additional colour identification should also be added. Long after any colouring has faded or end tags have disappeared, continuous and permanent face branding alone will provide a more reliable option for ongoing recognition of timber treatment in framing.
Continuously branded timber without associated colour pigmentation is strictly outside the Standard and Acceptable Solution at this stage. However, MBIE is of the view that continuous face branding alone (in accordance with Table 5.1 and cl 5.1.3 and 5.1.4 of NZS 3640) is compliant with the Building Code as an alternative solution.