In sub-flooring, which type does not have joints over the joists?

In sub-flooring, the type that does not have joints over the joists is tongue and groove. This design features boards that are manufactured with grooves along one side and tongues on the adjacent side. When these boards are fitted together, the tongue of one board fits snugly into the groove of another. This connection allows for a more stable and uniform surface, as the joints are staggered rather than aligning directly over the joists. This arrangement enhances the sub-floor's structural integrity and reduces the potential for squeaks or movement.

In contrast, other types of sub-flooring, such as square edge and butt joints, often have seams that can align over the joists, which may lead to instability. Square edge boards fit together without interlocking mechanisms, and butt joints involve two boards butting against each other, which can create weaknesses at the joints if they fall directly over a joist. Therefore, the tongue and groove design is particularly advantageous for creating a stable and robust sub-floor system.