Timber Joist Span Calculator (Indicative)
Assumptions: domestic floor, joists at selected centres, imposed load ≈ 1.5 kN/m², dead load ≈ 0.5 kN/m², service class 1–2, joist breadth ≈ 47 mm, minimum bearing ≈ 40 mm. Spans shown are clear spans (support-to-support).
Max indicative clear span:
—
(based on selections)
Span Table
| Section Size (mm) | C16 – Max Clear Span (m) | C24 – Max Clear Span (m) |
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Usage notes: If supporting a lightweight partition perpendicular to joists, reduce spans by ~10%. For partitions running parallel, double up joists beneath the partition line. Notching/holes reduce capacity—follow current guidance.
Disclaimer: This tool is for guidance only and may not reflect the latest building regulations, standards, or your specific loading. Always verify with current codes and a competent designer. For approvals, please contact your local authority / Building Control.