Performance of finishes on western juniper lumber and particleboard during outdoor exposure

The increasing number of western juniper trees per acre and the expansion of its range is resulting in watershed degradation, loss of site productivity, decrease in forage production, loss of wildlife habitat, and overall reduction in biodiversity. Previous studies and anecdotal evidence indicate western juniper has fairly good resistance to decay and insect attack, and it might be suitable for decking and siding applications as well as for particleboard furnish. We evaluated the performance of smooth-planed and saw-textured western juniper lumber and particleboard finished with a variety of paints and stains. Our objectives were to evaluate substrate stability (resistance to checking and warping), aboveground durability, and susceptibility to discoloration and mildew growth. We found that the performance of western juniper is similar to that of other highly colored and dimensionally stable wood species such as western red cedar. Western juniper is somewhat prone to mildew and extractives bleed through some paints. The two-coat latex paint was effective in blocking extractive bleed from lumber, but discoloration was a serious problem with particleboard. Clear penetrating finishes lasted only 1 to 2 years, and semitransparent finishes performed well only on saw-textured lumber. Two-coat, film-forming finishes gave excellent performance on both smooth-planed and saw-textured lumber.

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