Joist parameters
Enter your lumber species, size, and spacing — diagram updates live
IRC R507.5▲ Plan view (overhead)
▶ Cross-section (end view)
Both diagrams update when you change species, size, or spacing — enter your span to see pass/fail
Distance between supports
🇨🇦 Canadian mode coming soon. In Canada, deck joist spans are governed by the National Building Code (NBC) Table A-9.23.4.2 and Canadian Wood Council (CWC) span tables, which differ from IRC. Values and species groups are not identical to the US table. A dedicated Canada mode is under development — for now, use the CWC Wood Design Manual or consult your local AHJ.
🛒 Building your deck? Find lumber and hardware:
⚠️ Span values are based on IRC 2021 Table R507.5 for residential decks (40 psf live load, 10 psf dead load). Always verify with your local AHJ and a structural engineer for complex projects, hot tubs, or loads exceeding 40 psf.
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