Radiata pine heartwood billets, 50 x 100 x 1000 mm³ were end-sealed and treated with copper-chrome-arsenate preservative (NZ Type I) to a range of retentions and penetration patterns. Cross-sections, 10 mm thick, were cut from the centre of each billet and used for determination of preservative distribution, for preservative analysis and for decay tests. The decay test consisted of laying samples on the surface of soil beds in the FRI Fungus Cellar to induce decay of untreated and sub-threshold treated regions of samples. Location and extent of decayed areas in each sample were measured and their effect on residual strength properties were calculated using a computer programme orginally developed to determine the effect of cross-sectional defects on strength properties of laminated beams. Results showed that depending on the location of the decayed area, up to 14% of the cross-section could be lost through decay without significant loss of strength and over 30% could be lost while retaining 80% residual strength and stiffness. Relationships were also established between extent of decay, preservative retention and preservative distribution to demonstrate that compliance with local timber treatment specifications did not necessarily guarantee the timber's immunity from decay.

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