CSLB General Building (B)Framing and CarpentryHard
An engineer specifies Structural I plywood, rather than standard sheathing-grade plywood, for shear wall panels in a high seismic design category. What is the primary structural reason for this specification?
- AStructural I plywood is required only for fire-resistance purposes
- BStructural I plywood has higher allowable shear capacity due to stricter veneer grade and grain orientation requirements
- CStructural I plywood is lighter and easier to install on tall walls
- DStructural I plywood eliminates the need for edge nailing
Show answer & explanationAnswer & explanation
Correct answer: B. Structural I plywood has higher allowable shear capacity due to stricter veneer grade and grain orientation requirements
Structural I plywood is manufactured with all plies of a minimum grade and specific cross-grain orientation, giving it higher allowable shear values than standard sheathing plywood. This makes it preferable for shear walls resisting high seismic or wind lateral loads, where maximizing wall shear capacity per foot is critical.
Why the other options are wrong
- A. Fire resistance is not the purpose of the Structural I designation.
- C. Weight and ease of installation are not the governing structural reason.
- D. Edge nailing is still required regardless of panel grade.
Structural I Plywood
A plywood grade manufactured with stricter veneer quality and grain orientation controls, giving it higher allowable shear values than standard sheathing plywood, often required for high-demand shear walls.
- Higher published shear capacities than CDX sheathing
- Required in high seismic/wind shear wall designs per engineering
- All plies meet minimum strength/grain requirements
Memory trick: Structural One, strength has begun.