Exposure durability classifications are assigned on the basis of raw material composition and adhesive bond durability. Panels are typically produced to one of two classifications: Exterior or Exposure 1.
Exterior panels are designed for applications subject to permanent exposure to weather or moisture. They are fully waterproof. Exposure 1 panels are suitable for uses that are not permanently exposed to the weather, but where panels must resist effects of moisture due to construction delays, high humidity, or other conditions of similar severity. Exposure 1 panels have a fully waterproof bond and are made with the same exterior adhesives used in Exterior-rated panels. However, building products distributors and builders are cautioned to store panels on skids off the ground and to tarp the unit when there is potential of heavy rain or snow.
In the case of plywood, Exterior-rated panels are manufactured with C-C and better grade veneers, while Exposure 1 panels are classed as "Interior with exterior glue" panels because they can be constructed with veneer of D grade and better.