Performance of wood-based composites in a protected aboveground test in southern Japan
Five kinds of untreated wood-based composites (medium density fiberboard, hardwood plywood=HP, softwood plywood, particleboard and aspen oriented strand board, hereinafter abbreviated as MDF, HP, SP, PB and OSB, respectively) were exposed to subterranean termites and microbial (decay) attack under protected aboveground conditions in a southern part of Japan (Kagoshima Prefecture) for six years. Annual visual inspection was conducted and the degree of biological attacks was rated according to the AWPA standard since installation.
As expected, both biological attacks generally developed with time. However, none of MDF, HP and PB specimens sustained decay attack even after six years’ exposure. Termites started attacking wood-based composites earlier and the severity of attack was higher than decay fungi. This was common to all tested wood-based composites in the current field evaluation. A few specimens showed low resistance to subterranean termites. The first failure was noticed on one of OSB and two SP samples after three years’ exposure due to delamination and/or destruction caused by termites. MDF performed best, and followed by HP, PB SP and OSB, although they were unexceptionally attacked by termites. These results suggest the necessity of protective treatment to ensure a longer service life of wood-based composites even for an aboveground use when it is supposed to be conducive to biodeterioration.