APA Rating
An APA rating is the performance certification stamped on structural wood panels by APA — The Engineered Wood Association, indicating the panel's span rating, exposure durability, species group, and manufacturing standard compliance.
In Detail
APA Rating System
APA — The Engineered Wood Association is the primary third-party certification body for structural wood panels in North America. An APA-rated panel has been manufactured, tested, and certified to meet specific performance standards (PS 1 for plywood, PS 2 for all structural panels).
The APA grade stamp includes:
- Panel grade or span rating (e.g., "32/16" or "Rated Sheathing")
- Exposure durability classification (Exterior, Exposure 1, Exposure 2, Interior)
- Panel thickness
- Mill number (identifies the manufacturing facility)
- APA trademark (the certification mark)
- Manufacturing standard (PS 1, PS 2, or both)
Building inspectors look for the APA stamp to verify that installed panels meet code requirements. Panels without an APA stamp (or equivalent ESR certification) may not be accepted for structural applications.
Related Terms
Span Rating
A span rating is the pair of numbers stamped on structural panels (like 32/16) indicating the maximum recommended center-to-center spacing of supports — the first number for roof rafters and the second for floor joists, both in inches.
Structural I
Structural I is a premium APA panel designation indicating the panel is made exclusively from Group 1 wood species (strongest species group) and has enhanced cross-panel properties, providing higher shear and racking resistance for demanding structural applications.
Related Materials
CDX Plywood
This is a test description for CDX plywood as we work on the technical backend of the website.
OSB (Oriented Strand Board)
Oriented strand board (OSB) is an engineered wood panel made from compressed wood strands bonded with waterproof resin. It is the most widely used structural sheathing panel in North American residential construction, offering uniform strength properties and lower cost than plywood.