While there are decades of experience with borate-treated wood in coated, exterior applications in New Zealand and the UK, other countries have been more reluctant to use this process. As part of a research program on the potential use of borates by the Canadian wood products industry, Forintek set up, in 1990, an L-joint test of untreated and borate-diffusion treated hem-fir (western hemlock and amabilis fir). The treated material had a low initial retention of only 0.2% boric acid equivalent. The borate treated L-joints showed no signs of decay for 7 years, and after 10 years only 12% showed signs of decay. None had failed. In contrast 93% of the untreated L-joints showed signs of decay after 10 years and two thirds had failed. These field test results confirm those obtained from practical experience, considering that the L-joint test represents a higher leaching and biodeterioration hazard than a window.

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