Direction of Face Grain
For greatest strength and stiffness, plywood should be installed with the face of grain perpendicular to the supports. Section properties parallel to the face grain of the plywood are based on panel construction which gives minimum values in this direction. Properties perpendicular to the face grain are based on a usually differ
ent panel construction, which gives minimum values in that direction (Figure 1.6).
For design purposes, calculations must take into account in which direction the stresses will be imposed in the panels. If stresses can be expected in both directions, then both the parallel and the perpendicular direction should be checked.