Young Curly Brunette Girl Naked On The Floor

Floors in woodframe homes are usually constructed with joists centered no more than 16 inches or 40 centimeters apart, according to most building codes. Heavy floors, such as those made of stone, require more closely-spaced joists. If the span between load-bearing walls is too long for joists to safely support, then a heavy crossbeam (thick or laminated wood, or a metal I-beam or H-beam) may be used. A "subfloor" of plywood or waferboard is then laid over the joists.
Utilities
In modern buildings, there are numerous services provided via ducts or wires underneath the floor or above the ceiling. The floor of one level typically also holds the ceiling of the level below (if any).