The Definition for Joist Spacing for Wood Floors

Joist Spacing

• Wood floor joist spacing refers to the standard distance between each individual floor joist. It is measured from the center of one joist to the center of the next joist. Even joist spacing ensures that floor joists are parallel to one another and also parallel to the rim joists, which form the outer edge of the floor's structure. Common joist spacing can be anywhere from 12 inches to more than 24 inches.

Determining Spacing

• Joist spacing for a particular construction project depends on a number of factors. One is the type of wood used for the joists. In general, larger pieces of lumber allow for larger joist spacing since each joist can support more weight. The number of vertical posts that support the home, as well as the general structural design, also impact joist spacing. Builders use data tables and advanced computer models to determine joist spacing for specific projects.

Weight

• Joist spacing is important because floor joists are responsible for supporting the weight of the floor, home contents and people within the home. The weight that a system of floor joists needs to support is measured in pounds per square foot, or psf. This consists of a dead load and a live load. The dead load refers to permanent weight from the floor and upper portions of the home's structure. Live load, which is usually much more than the dead load, includes people, appliances, home contents and the added weight and pressure that come from earthquakes, wind, snow and rain falling on the home.

Considerations

• Home builders design and install floor joists using spacing that is more than sufficient for the expected weight. However, using more material raises construction costs and slows down the building process. Unnecessary floor joists also limit options for installing stairways. This means that architects and builders are searching for the most open floor joist spacing that will still provide structural integrity. Consult with a professional before altering floor joist spacing in your home or installing new joists for an addition.