The effects of different kerfing and center-boring treatments on the checking of ACQ treated pine posts exposed to the weather

There is interest in Australia in using kerfing and center boring to reduce the checking of preservative-treated posts, but information to optimize su ch treatments for radiata and slash pine posts is unavailable. In this stud y, a variety of single- and double-kerfing and center-boring treatments wer e applied to untreated green 125- or 150-mm diameter radiata pine and slash pine posts. Kerf depths and the diameter of center-bored holes were varied , and posts were either air- or kiln-dried before they were pressure treate d with an ammoniacal copper (ACQ) wood preservative. Treated posts were exp osed to the weather for I year in Canberra, Australia, and the number and s ize of checks in the posts were then assessed. Increasing the depth of kerf in double-kerfed posts resulted in significant decreases in the sizes of c hecks and, with the exception of 150-mm-diameter radiata pine posts, the nu mber of checks. The effect of increasing kerf depth or the diameter of the center-bored hole on checking in single-kerfed and center-bored posts, resp ectively, was less pronounced. Overall, kerfing was more effective than cen ter boring in reducing the number and sizes of checks that developed in exp osed posts. Posts that were kiln-dried at high temperature before treatment , but after kerfing or center boring, developed shallower checks than posts that were air-dried before treatment. The smaller posts (125 mm in diamete r) developed shallower checks than the larger posts (150 mm in diameter). H owever, in general, the effects of wood species, post diameter, and drying method on checking were small compared with the effects of kerfing or cente r boring.