How Far Apart Are Floor Joists: Essential Guidelines and Tips

July 9, 2024

Floor joists are essential structural components in building floors, spanning across open spaces between load-bearing walls and structural beams. These joists need to support the anticipated load for the building over long durations to ensure stability. An important aspect to consider is how far apart are floor joists, which typically range from one to two feet apart. The required depth of these joists increases with spacing to manage stress and prevent deflection.

how far apart are floor joists
"Level floor joists" by wheezinggirl is licensed under CC BY 2.0. To view a copy of this license, visit

How Far Apart Are Floor Joists: Key Considerations

The spacing of floor joists is crucial in determining the support and stability of any floor or shed. For residential constructions, floor joists are generally spaced 16 inches on center. However, floor joists for sheds can be spaced 12 inches O/C, 16 inches O/C, and sometimes 24 inches apart, depending largely on the intended use and load requirements. Remember that a general rule for sizing joist depth is taking half of the intended joist span in feet, adding two, and using that number in inches.

Consulting with a structural engineer or a local building inspector is highly recommended to ensure that the chosen size and spacing of floor joists meet local building codes based on your specific project needs.

how far apart are floor joists
"DURING- foundation is complete, the engineered floor joists have been set, and the plywood subfloor is now ready to be installed" by NLT CONSTRUCTION is licensed under CC BY 2.0. To view a copy of this license, visit

Using a Floor Joist Calculator

A floor joist calculator is an invaluable tool for any flooring or deck framing project. This calculator can determine the number of floor joists needed and estimate the material cost, effectively serving as both a floor joist span calculator and a cost calculator. By inputting the joist span and spacing into the calculator, you can get an accurate estimate of the maximum allowable span and ensure that your construction meets safety and stability standards.

For best results, follow these steps when using a floor joist calculator:

  • Measure the span and intended spacing for the joists.
  • Input these measurements into the calculator along with the anticipated load requirements.
  • Use the results to select appropriately sized and spaced joists.

Tips for Choosing the Right Floor Joists

When choosing the right floor joists, consider the following tips:

  • Ensure proper spacing to support the load: How far apart are floor joists will affect the structural integrity – tighter spacing provides more support.
  • Select the right material: Engineered wood joists, like prefabricated I-joists, offer additional strength and stability compared to traditional lumber.
  • Reduce stress with blocking: Inserting smaller pieces of wood between joists can enhance overall floor stability.

how far apart are floor joists
"Floor joists" by retropc is licensed under CC BY-NC-SA 2.0. To view a copy of this license, visit

Addressing Structural Issues

Over time, issues such as widely spaced joists can lead to structural problems like floor creaks or sagging. One case showed a 50-year-old house with cracking subfloors due to far-apart joists. Temporary fixes, like screwing 2x4s to the underside, failed to resolve the issue. If you face similar problems, consider major repairs such as replacing the subfloor or sistering the joists to strengthen the structure. For significant concerns, always seek professional advice.

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