FIELD DURABILITY OF CCA-TREATED AND ACA-TREATED PLYWOOD COMPOSED OF HARDWOOD AND SOFTWOOD VENEERS

Current American Plywood Association standards for plywood panel produ cts are based on structural performance and allow hardwood veneers to be included in southern pine plywood. However, the American Wood Prese rvers' Association's (AWPA) standard for permanent wood foundations re quires that plywood be made only of softwood plies. Hardwoods are gene rally more difficult to protect from decay using waterborne preservati ves than are softwoods. The objective of the study reported herein was to document field performance of plywood composed of both hardwood an d softwood veneers treated with waterborne preservatives and to determ ine if AWPA requirements are warranted. Results are given for hardwood -and softwood-treated plywood tests after 10 years of ground exposure in southern Mississippi. With reference to southern pine plywood and t he current AWPA standard for preservatively treated wood used in perma nent foundations, we conclude that the requirement that plywood be com posed only of softwood plies is prudent.