AWPA refreshes ground contact standards
New standard changes by the American Wood Protection Association will kick in May or June of this year when the AWPA 2016 Book of Standards is printed, offering more explicit guidance on the degree of protection required for “above ground” or “ground contact” materials.
In essence, the new standards lean more toward the side of higher preservative retention levels of treatment when dealing with ground contact wood and wood-based materials.
It has always been the case that wood materials used in contact with the ground, fresh water, or other situations favorable to deterioration fell into the UC4A Ground Contact category, requiring higher preservative retention levels of wood preservation treatments. The AWPA’s UC3 categories for above-ground uses require less treatment, as stands to reason.
The new standard elaborates on those “other situations favorable to deterioration,” which may be above ground. The UC4A standard states that above-ground wood and wood-based materials that are crucial to the performance of the structure (of a deck, for instance) and are difficult to replace, or may someday come in contact with the ground fall under the higher UC4A category.
While the UC4A standard had always cited examples of fence posts, deck posts, guardrail posts, structural lumber and timbers for UC4A guidance, the new standard adds “joists and beams for decks and freshwater docks.”
As points of emphasis, the new standard spells out six above-ground instances where the UC4A standard comes into play:
A “reasonable expectation” for soil or vegetation to accumulate in contact with the building component;
When air can’t circulate underneath the construction and between decking boards;
When components are less than 6 inches above ground and supported on permeable materials (concrete or treated wood);
When in components are in direct contact with non-durable untreated wood;
When components get wet frequently, as in a floating dock; and
In a tropical climate.
Furthermore, standards are expected to take effect sometime in the late second quarter of 2016. From there, it remains to be seen how, if or when the AWPA’s guidance will work its way into local building codes.