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.
In Detail
What Is Structural I?
Structural I is an APA panel designation that indicates superior structural properties compared to standard rated panels. To qualify for the Structural I designation, panels must be manufactured exclusively from Group 1 wood species — the strongest species group, which includes Douglas Fir-Larch, Southern Pine, and Western Larch.
The key advantage of Structural I panels is enhanced cross-panel strength. Because all plies use the strongest species, the panel's properties are more uniform in both the strong axis and cross-panel directions. This matters most in shear wall applications where the panel must resist racking loads from multiple directions.
When to Specify Structural I
- High-wind zones (Vasd ≥ 130 mph) where enhanced shear wall capacity is needed
- Seismic Design Categories D, E, and F where lateral force resistance is critical
- Engineered shear wall designs that require specific panel shear values above standard rated panels
- Diaphragm designs where cross-panel capacity affects the engineering
Related Terms
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.
Shear Strength
Shear strength is the maximum stress a material can withstand before failing along a plane parallel to the applied force — in construction, this determines how well a structural panel or shear wall resists lateral loads like wind and seismic forces.
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