The two types of plywood available are Rated and Structural One, but for shear wall use the plywood must have 5 plies. Rated Plywood can be made of any species of wood, while 10% stronger Structural 1 must be made of denser Southern Pine or Douglas Fir.  Overall it is not that big a deal if you use Rated instead of Structural one.


3 ply plywood tore in Northridge Earthquake

Plywood made with only 3 plies tore in the 1994 Northridge Earthquake and should not be used.

Shear walls made of 3 ply plywood tore in the Northridge Earthquake so the City of Los Angeles downgraded  the acceptable limits for 3-ply plywood to a maximum of #200 plf.  On page 10 of the Wood-Frame Subcommittee Findings Report published immediately after the Northridge Earthquake it says: “The performance of 3-ply construction has raised questions of its ultimate capacity.  Horizontal tearing has occurred on some outer face plies above the inner ply seam.  Values for all 3-ply panel construction were therefore reduced to 200lbs/ft maximum.”