Joist
Definition and meaning of Joist in real estate.
Joist refers to a horizontal structural member run in parallel series to support a floor, ceiling, or roof framework.
In more detail
Joists span the open space between walls, beams, or foundations, transferring the weight of the floor or ceiling to the primary load-bearing walls. In typical residential framing, joists are placed on edge and spaced at standardized intervals, such as sixteen or twenty-four inches from center to center.
The size and spacing of joists depend on the span length, the weight they must support, and local building codes. Properly sized and spaced joists prevent floors from sagging or feeling bouncy when walked on.
Key facts
| Category | Property Types & Construction |
|---|---|
| Common spacing | Typically sixteen or twenty-four inches on center |
| Material types | Dimensional lumber, engineered I-joists, or steel |
| Required by | Local building codes and engineering specifications |
During the construction of a two-story home, carpenters install wooden joists across the first-floor walls to create the framework that will support the second-floor plywood subfloor and carpet.
Frequently asked questions
What is the difference between a joist and a beam?
A joist is a smaller structural member that directly supports a floor or ceiling. A beam is a larger, primary support that holds up the joists and transfers their load to posts or foundations.
Why do floors sag or bounce?
Floors typically bounce or sag because the joists are undersized, spaced too far apart, or damaged by moisture, wood-boring insects, or improper cutting during plumbing installations.