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Floor Joist Span Calculator

The SkyCiv floor joist span calculator allows you to calculate the maximum span of timber joints. The calculations in this tool are based on the American Wood Council’s standards. The floor joist calculator considers factors including the joist size, thickness, height, wood type, and wood grade as well as loading and deflection factors. Various common types of wood and grades are available within the below floor joist spacing calculator.

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About the Flooring Joist Span Calculator

How to use the floor joist span calculator?

To begin using the floor joist calculator enter the details of the joist on the left-hand side. These details will include:

  • Joist Size
  • Joist Thickness
  • Joist Height
  • On-Center Spacing

Then complete the advanced details including:

  • Wood & Grad
  • Deflection Limit
  • Load per Area Unit

Run the floor joist spacing calculator to determine the maximum span

Flooring joist calculator assumptions and limitations:

  • This tool supports only natural solid lumber joists
  • This tool uses the American Wood Council’s standards for reference. ‘
  • These calculations are only approximations and should be used as the starting point to get an idea about the Joist Span.

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Flooring Joist Span Calculator FAQs

Your Questions Answered

What is a floor joist?

Site classification is a metric used to categorize the expected movement of a founding material following changes in moisture content. The higher the expected movement, the stiffer the slab on grade needs to be to avoid cracking. AS 2870 has 7x site classifications which are tabulated below.

A floor joist is a member that supports the weight of a floor and loads placed on a floor. These are horizontal structural members that are found parallel to the ground and help distribute the weight to the underlying structural foundations. Flooring joists are vital to the stability and strength of a floor structure. The above flooring joist calculator can be used to determine the appropriate size of joists depending on loading and other factors.

Floor joist span tables are references used by engineers, builders, and construction workers to estimate the appropriate size of joists based on factors such as the joist parameters and floor loading. The above floor joist calculator can be used in place of a floor joist span table.

The on-center spacing is the spacing between each joist. Generally, the larger the spacing (distance between each joist) then the lower the maximum allowable span is.

Floor joist span calculators and tables can be used for LVL timber as long as considerations around the material properties and behavior of the lumber are taken into account.

Yes, floor joist span calculators and tables can be used for deck design as long as all considerations are taken into account.

Yes, floor joist tables are generally available for timber floor joists. The correct table needs to be used based on the type of wood, lumber, or timber joist. Alternatively, the above floor joist spacing calculator contains options for many types of wood including:

  • Alaska Cedar
  • Alaska Hemlock
  • Alaska Spruce
  • Alaska Yellow Cedar
  • Aspen
  • Baldcypress
  • Beech-Birch-Hickory
  • Coast Sitka Spruce
  • Cottonwood
  • Douglas Fir-Larch
  • Douglas Fir-Larch (North)
  • Douglas Fir-South
  • Eastern Hemlock-Balsam Fir
  • Eastern Hemlock-Tamarack
  • Eastern Softwoods
  • Eastern White Pine
  • Hem-Fir

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