Five-year performance ratings are presented for two types of untreated, uncoated wood joints (L and lap) in aboveground tests under shaded conditions. The effect of shading on moisture entrapment in pine and maple L and lap joints was evaluated in a moderate decay zone (Madison, Wisconsin). Variations were observed between wood species, visual ratings, joint type, moisture content readings, and fungal growth on the specimens. Representative fungal fruiting bodies were identified as members of the Peniophorella praetermissa species complex by microscopic and DNA analyses. After 5 years, the highest average rating (indicative of most severe deterioration) occurred in white pine L-joint specimens followed by maple lap joints and maple L joints. Pine and maple L-joint specimens demonstrated considerably lower rating variation between specimens compared with lap-joint specimens. White pine lap joints shaded with a tarp had lower average moisture content but showed similar average ratings to pine lap joints shaded by a tree. Regardless of the shading method, white pine lap joints had the lowest average decay rating. Under shaded conditions in a moderate decay zone, untreated and uncoated L-joint performance was notably more uniform from specimen to specimen than lap-joint performance following 5 years of outdoor exposure. A single-point moisture content taken at the time of inspection was not a reliable indicator of the degree or rate of decay for aboveground joint test assemblies evaluated in this study. Likewise, uniform specimen wetting or drying is not predictable under shaded conditions.

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Author notes

The authors are, respectively, Supervisory Research Microbiologist and Research Plant Pathologist, USDA Forest Serv., Forest Products Lab., Madison, Wisconsin (, This paper was received for publication in March 2011. Article no. 11-00040.