Effect of weathering on surface quality and structural properties of six species of untreated commercial plywood siding after 6 years of exposure in Alabama

The effect of 6 years of outdoor exposure on untreated and unstained 5/8-in ch commercial plywood siding in Alabama was determined. The study was parti cularly concerned with the effect of weathering on attractiveness and disco loration of original surface color, surface quality, delamination, and on p ercent of retention of original strength properties. Considering the color, surface quality, and the retained mechanical properties of the exposed spe cies, the Douglas-fir plywood ranked best. The redwood panels lost their mo st important asset, the attractive initial color. The baldcypress panels de veloped some surface checking but had no decay and maintained a high streng th ratio. The southern yellow pine panels developed severe surface checking and decay. The lauan panels were the worst of all with severe checking, de cay, and the lowest retention of mechanical properties. The results suggest that plywood siding should be surface treated on the job with a quality st ain or paint.