Exposure durability classifications indicate suitability of wood structural-use panels for end-use applications. Panels qualify for one of two exposure durability classifications — Exterior or Exposure 1 — on the basis of raw material composition and adhe sive bond durability. As defined in the Classification sections of US Department of Commerce Voluntary Product Standards PS 1 and PS 2:

• Exterior panels are suitable for applications subject to repeated wetting and redrying or long-term exposure to weather or other conditions of similar severity.
• 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. Still, Exposure 1 panels have a fully waterproof bond and are made with the same exterior adhesives used in Exterior-rated panels.

In the case of plywood, Exterior-rated panels are manufactured with C grade and better veneers throughout the entire panel, while Exposure 1 panels were formerly identified as “Interior with Exterior Glue” because they can be constructed with veneer of D grade and better.

Gradestamps applied to certified structural-use panels must include the exposure durability classification, as shown in examples of gradestamps contained in our TECH TIP library, such as the TECH TIP on PS 1 and PS 2 Gradestamps.

Regardless of exposure durability classification, building products distributors and builders are cautioned to store p anels on skids off the ground and to tarp units when there is potential of heavy rain, snow, or construction delays. For additional information on this topic, please see our TECH TIP on Panel Handling and Storage.