5/8"-4'x8' ORIENTED STRAND BOARD | Every Weyerhaeuser panel is strong, stiff, and stable-it's manufactured flat, installs flat, stays flat, and has been engineered to precise specifications to resist problems like cupping, warping, and sagging. Apply panels perpendicular to supports. Use appropriate fasteners at the recommended schedule and gap panels 1/8" on the ends and sides of each panel. All edges are sealed for moisture and weather resistance.This panel carries an Exposure 1 rating and is for limited exposure and must be covered. Each sheet is Association Grade stamped and also carries the span ratings. Check the Building Code for the application required in your area. Other manufacturers are substituted at times, Weyerhaeuser is our main supplier.