In ordinary wood-frame construction, which element provides the primary support for floors?

• A. Tied into bearing walls.
• B. Secured by pier and beam construction.
• C. Typically supported by joists.
• D. Fire rated and protected.

Answer: (C)

The key idea is that the floor is carried by the floor framing members called floor joists. These joists run across the room and bear on supporting members—usually a bearing wall, a beam, or a combination—transferring the load of the floor (dead load plus live load) down to the walls or beams and ultimately to the foundation. Even in pier-and-beam construction, the same path exists: the joists carry the floor and are supported at their ends by beams and piers below.

Understanding this helps you see why floor joists are the primary element for floor support. Other aspects mentioned—being tied into bearing walls describes how loads are transferred through the framing, the foundation type (pier and beam) describes what supports those beams, and fire rating concerns relate to safety, not the main structural support for the floor itself.