Ten-year performance of treated northeastern softwoods in aboveground and ground-contact exposures

Abstract

The commercial value of several softwood species of the northeastern United States could be increased if these woods could be treated to meet existing American Wood Preserversa Association (AWPA) Standards and used in durable structures. We evaluated the long-term durability of incised and unincised white pine, red pine, eastern spruce, balsam fir, and eastern hemlock treated with ammoniacal copper arsenate (ACA) and chromated copper arsenate (CCA1Type C). The treated wood was exposed above ground and in ground contact in the southern and northeastern United States. Simulated decks were tested above ground in Cumberland, Maine, and Amherst, Massachusetts. Stakes were tested in ground contact in Saucier, Mississippi, and Cumberland, Maine. Replicates of all test species and conditions, including untreated controls, were represented in the test plots and decks. Both the stakes and deck material were monitored annually for structural condition and appearance. After 10 years of aboveground exposure, all untreated decks (controls) failed as a result of decay. Wood treated with CCA showed somewhat better durability than did wood treated with ACA. Except for white pine, treated incised wood species showed no evidence of decay. Incised white pine treated with ACA failed by excessive checking. Unincised white pine treated with CCA also failed, as a result of transverse scaling and radial checking. In ground-contact field trials, failure patterns of untreated stakes showed more differences than did performance patterns of treated stakes at different exposure sites. Overall, these results suggest that treated northeastern softwood species could be used for durable construction.

Citation

Crawford, Douglas M.; De Groot, Rodney C.; Gjovik, Lee R. Ten-year performance of treated northeastern softwoods in aboveground and ground-contact exposures. (Research paper FPL ; RP-578):9 p. : ill. ; 28 cm.