Free Tool
Floor Joist Span Calculator
Look up the maximum span for a wood floor joist from the Ontario Building Code span table. Choose the species, grade, size, spacing and bridging, and check your span against it.
Floor Joist Span Calculator
Result
All sizes with these settings
Preliminary planning only. This tool does not replace the drawings. The designer or engineer of record and the building permit set govern every size, span and detail.
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Where the numbers come from
- Source. Table 9.23.4.2.-A, Maximum Spans for Floor Joists, General Cases, in Division B Part 9 of the 2024 Ontario Building Code. The values are read directly from the table.
- Span. Spans are measured from the inside face of one support to the inside face of the other, so enter the clear span, not the centre to centre distance.
- Strapping and bridging. Article 9.23.4.2. describes them: 19 by 64 mm strapping nailed to the underside of the joists, and cross-bridging or 38 mm solid blocking, placed not more than 2 100 mm from each support or other row.
- Not covered. Table 9.23.4.2.-B cases such as a concrete topping or a ceiling on wood furring, notched or drilled joists, point loads, engineered joists, stair openings and non-residential live loads need the other tables or a design.
- Conversion. Feet and inches are converted at 25.4 mm per inch. The maximum span is shown rounded down to the whole inch.
This tool is for preliminary planning. The designer or engineer of record and the building permit set govern.
Frequently asked questions
How far can a 2x10 floor joist span in Ontario?
It depends on the species group, grade, spacing and whether bridging or strapping is installed. For Spruce-Pine-Fir No. 1 and No. 2 joists of 38 by 235 mm at 400 mm on centre with strapping, Table 9.23.4.2.-A of the 2024 Ontario Building Code gives 3.96 m. The calculator reads the table for your exact inputs.
What does the table assume about the floor?
The spans apply only where the floor serves residential areas as described in Table 4.1.5.3., or where the live load does not exceed that for residential areas. They do not cover concentrated loads, concrete topping, ceilings on furring or other special cases. Those are covered by Table 9.23.4.2.-B or need design.
Is the span measured centre to centre of the bearings?
No. Maximum spans in the Part 9 span tables are measured from the inside face of one support to the inside face of the other, so it is the clear span between supports.
What do strapping and bridging change?
Strapping is 19 by 64 mm strips nailed across the underside of the joists, and bridging is cross-bridging or solid blocking between them. Both stiffen the floor and allow a longer span in the table. Article 9.23.4.2. sets the size and spacing of each.
Does passing the table mean the floor will feel solid?
Not always. The table is a code minimum. Longer spans can feel bouncy, and many builders choose a deeper joist, closer spacing or an engineered joist for a stiffer floor. The designer decides.
Is this a quote?
No. It is a planning tool. Contact us with your plans and we will arrange a free site visit.
For subfloor, I-joists and squeaks, read Floor Framing: Joists and Subfloor.
Related: Floor and joist systems, Subfloor and sheathing, Lumber and board foot calculator.
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