Dimension Ratios
The International Building Code (IBC) and the Uniform Building Code (UBC) place limits on the dimensions of wood-frame shear walls.  These restrictions are based on the poor performance of tall, narrow wood-frame shear wall segments observed in previous earthquakes. The limits are in the form of maximum height-to-width ratios (h:b).   The maximum allowable ratios are a function of the type of shear wall construction and the location (seismic zone) of the structure.  Much of the information in UBC Table 23-II-G is presented below.  Be sure to pay special attention to the footnotes as they may dictate your design.
Material Horizontal Diaphragms maximum. Span :Width  Shear Walls maximum Height :Width 1.  Diagonal Sheathing, conventional 3:1 1:11 2.  Diagonal Sheathing, special 4:1 2:12 3.  Wood Structural panels... nailed all edges 4:1 2:12,3 4.  Wood Structural panels... no blocking 4:1 not permitted 1 .In Seismic Zones 0, 1, 2, 3, the maximum ratio may be 2:1 2  In Seismic Zones 0, 1, 2, 3, the maximum ratio may be 3½:1 3  In Seismic Zones 4, the maximum ratio may be 3½:1 for walls not exceeding 10 feet in height on one side of the door to a one-story     Group U Occupancy
Topics of this module include: Introduction, Load Path, Segmented Design Method, UBC Design Table, Wall Shear, Chord Design, Anchorage, Deflection, Perforated Design Method, Method Comparison, Shear Wall Failures