What Is Floor Joist

The floor joist is nailed to the plate material and spans the open area under the floor.

What is floor joist.

Each type of wood has a specific span and spacing requirement. Floor joist spacing is the distance a floor joist board can be separated from an adjacent floor joist. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction. The floor sheeting is usually made from 3 4 or thicker sheets of plywood or osb.

The rim joist fig. Floor joists are an important part of the supportive structure of a floor. The floor sheeting is also engineered to provide a solid floor. They hold up the weight of a building absorb impacts on the floor and create structural support so that the floor will be stable and secure.

The width of a board is an important factor in determining the distance a floor joist can span playing a much larger role than the thickness. Joists span across the tops of load bearing walls and may be supported at mid span by a beam or other member. In the past 2x4s or 2x6s were sometimes used as floor joists. For example if you double the thickness or number of joists in a floor the distance the boards can span will increase by approximately 25.

B the framing member that runs around the perimeter of your house and that the floor joists butt into often gets riddled with large holes this space is the logical exit point for dryer and furnace vents big electrical service wires and fireplace fresh air intakes. This spacing is combined with a floor joist span to determine the maximum capacity load of a floor. In buildings with basements the first level of floor joists serves the same purpose. This size is no longer acceptable when framing a structure.

In building constructions the term joist refers to a horizontal framing member that is the primary structural element of a floor or ceiling frame. Floor joists installed on second or third or higher levels double as ceiling joists for the level below. They are covered with subflooring panels of plywood or oriented strandboard osb to complete the floor s structural assembly and create the solid continuous platform on which you install tile carpet or other finish flooring. Considering the cross section of a typical joist the overall depth of the joist is critical in establishing a safe and stable floor or ceiling system.

Joists are spaced at regular intervals much like the studs in a wall frame. Joists must exhibit the strength to support the anticipated load over a long period of time.