Shear Wall Height

The shear wall height H_S is the distance from the bottom of the bottom wall plate to the top of the top wall plate, exclusive of floor joists or other building elements not part of the wall. This height is shown in CSA O86 figure 11.7.

Gable End Walls

Note that this is the height used on the gable end of the building, even though the height to the sloping roof is used as the moment arm in hold-down force calculations. This height is used because -

• it corresponds to the storey height h_s used for allowable storey drift in storey drift calculations.
• the deflection equation assumes rectangular walls
• it can be assumed that the roof as a unit deflects the same amount as its juncture with the supporting wall

A slight discrepancy might occur in the case that the gable end wall is a tall wall composed of studs that extend to the roof, and there is no ceiling at eave height. The bending term in that case does not take into account the full length of the stud. However, the difference is small, and the bending term does not in general dominate.

However, judgment should be used in applying the deflection calculations to vaulted ceiling assemblies.