The Span Rating shows the maximum inches between supports members that the panel may be installed over. When there are two numbers, the first refers to roof applications, the second to floor applications. For example, the 32 means that the roof rafters may be a maximum of 32 inches apart on center. The 16 means that floor joists may be a maximum of 16 inches apart on center.

The Exposure Durability Classification defines whether the panel should be used for interior or exterior applications:

• Exterior panels have a fully waterproof bond and are designed for applications subject to permanent exposure to the weather or moisture.
• Exposure 1 panels are designed for protected construction and industrial applications and can be exposed to the elements for a short time, but not permanently.
• Exposure 2 panels are intended for protected construction and industrial applications where the potential for conditions of high humidity and water leakage exist.
• Interior panels are manufactured with an interior grade glue and are intended for interior applications only.

The thickness of the panel is also included on the stamp.

Information courtesy of Georgia-Pacific