INTRODUCTION Structural wood panels, primarily consisting of engineered plywood and oriented strandboard (“OSB”) products, dominate the exterior sheathing market. The most common panel size is 4x8 feet, with typical thicknesses ranging from 3/8-inch to more than 1 inch. Plywood structural panels may be performance-rated according to the provisions of voluntary product standard PS-1-951, published by the National Institute of Standards and Technology (NIST). OSB structural panels may be rated according to the provisions of NIST voluntary product standard PS-2-922. However, similar rating standards are also published by governmental agencies in Canada and Japan and by APA – The Engineered Wood Association, and other structural panel trademarking organizations.