Recommended installation of sheet subflooring over joists is:

The recommended installation of sheet subflooring over joists is perpendicular to the joists. This method is essential because it helps to maximize the structural integrity and stability of the flooring system. Installing subflooring perpendicular to the joists provides a larger surface area for the fasteners, which results in a stronger bond and minimizes the risk of movement or squeaking over time.

Furthermore, by orienting the subflooring in this manner, you distribute the load more evenly across the joists, enhancing the overall strength of the floor structure. It also helps in reducing the possibility of sagging or warping that might occur if the subfloor was installed parallel to the joists, where support might be less uniform.

Selecting this orientation is standard in carpentry and construction practices, and it complies with building codes that emphasize proper installation techniques to ensure safety and durability in flooring systems.