In the mid 1990s, Forintek Canada Corp. initiated a study of the termite resistance of borate-treated lumber above ground, protected from rain in Canada, Japan and Hawaii. Predominant termite species at three test were Reticulitermes flavipes in Canada, and Coptotermes formosanus in both Japan and Hawaii. The material included hemlock and amabilis fir lumber treated with disodium octaborate tetrahydrate and chromated copper arsenate (CCA) and local reference materials. In Canada all of the treated material was found to be performing equally well after ten years, with some pieces showing residual signs of early superficial nibbling or cosmetic damage. Attack was moderate on untreated controls. Similar results were found in Japan with the exception of 2% borate shell treatments with DDAC in which two samples were rated as moderately or severely attacked. In Hawaii, where termite attack was more severe 2% and 3% BAE (boric acid equivalent) borate through treatments and ammoniacal copper zinc arsenate performed better than the other treatments. The tests in Japan and Hawaii were terminated after ten years. CT scanning of the Hawaii samples revealed the 3% through borate treatments contained the least termite damage and 2% through borate treatments had negligible attack. Compression stiffness testing of Hawaii borate treated samples showed only the 2% shell treated samples showed statistically significantly lower stiffness than the 3% through treated samples which had no internal damage. Chemical analysis of Hawaii and Japan samples showed the amount of borate retained was less on the outer surfaces, particularly on the top and sides. There was no correlation between the treatment type and the percentage of borate retained, or between the rating given the piece for decay and the percent of borate retained. The results demonstrate that borate treatments can provide long-term protection from destructive termite attack to structural lumber. A 2% BAE through-treatment performed better than CCA treated hem-fir in Japan and Hawaii.

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