What is the reason that each layer in a sheet of plywood is oriented perpendicular to the others?

The layers in a sheet of plywood are oriented perpendicular to one another primarily for strength. This construction technique significantly enhances the overall structural integrity of the plywood. By alternating the grain direction of each layer, the plywood gains improved resistance to warping, splitting, and delamination. This arrangement helps to distribute loads evenly across the surface, making the product stronger and more stable compared to solid wood of the same thickness.

While other factors like thickness, aesthetic considerations, and ease of cutting do play a role in plywood design and usability, the orientation of the layers is fundamentally aimed at optimizing strength and durability in construction applications. The perpendicular layering directly contributes to plywood's capability to bear weight and withstand stress, which is critical for its use in various building projects.