Partition walls (nonload-bearing walls):

Partition walls, which are nonload-bearing walls, are best if they are constructed perpendicular to the floor joists below. This orientation helps distribute any minor loads from the partition wall more effectively across the joists. When a partition wall is perpendicular to the joists, it reduces the risk of loading the joists unevenly, which can lead to sagging or structural issues over time.

In residential construction, the proper configuration of partition walls is essential for maintaining the integrity of the flooring system. Since these walls do not support the roof or upper levels, their primary role is to separate spaces. Constructing them perpendicular provides a stable arrangement, minimizing stress on the joist system.

The other options, while they mention valid construction principles, do not optimize the performance and safety of the floor system associated with partition walls as well as the suggested perpendicular orientation does. Choosing the right alignment for any wall is crucial for the durability and safety of the structure.