When installing tongue and groove plywood subflooring, in which direction should the grain run?

When installing tongue and groove plywood subflooring, the grain of the plywood should run parallel to the joists. This orientation is crucial because it provides the necessary strength and stability to the floor structure. Plywood is engineered with layers of wood, and when the grain runs with the joists, it maximizes support and minimizes sagging or bending since the weight is distributed across the joists.

Additionally, arranging the plywood with the grain aligned to the joists helps prevent potential warping and enhances the overall performance of the flooring system. By ensuring this alignment, installers can also facilitate proper fastening and reduce the likelihood of cracks or failures in the subfloor under load.