Abstract
The Australian National Standard for the preservative treatment of wood (Standards Australia, AS/NZS1604.1) defines the penetration zone and the preservative retention that must be present in the penetration zone for each of six hazard classes.
For Hazard Class H3 (AS/NZS 1604.1) sawn structural members 35 mm thick or less, and of natural durability classes 2, 3, or 4 (AS/NZS 5604.2), the penetration zone is all sapwood plus 5mm from any (heartwood) surface (a heartwood percentage area limitation applies).
The Standard allows the use of chemical indicators to determine the extent of sapwood and heartwood as well as preservative penetration. Preservative penetration indicators change colour in the presence of certain levels of a specific active ingredient (usually copper in copper containing preservatives or zinc used as a tracer in light organic solvent (LOSP) systems).
However, interpreting penetration patterns is subjective, and the National Centre for Timber Durability and Design Life (NCTDDL) initiated a project intended to create a guide to help interpret penetration tests.
A survey was conducted with 43 selected Australian and New Zealand timber protection industry professionals, who were asked to interpret 20 sets of copper penetration test photographs.
This report presents the results received.