Bardowl Pro Tools will be Live MON 8/10/26. Free tools are available now.
Size your deck joists, beams, ledger, guard posts, and stair stringers to the 2021 International Residential Code. Every value traces to a published code table. Built for Missouri jurisdictions, works anywhere the IRC applies.
The Deck Sizer runs inside the Bardowl Pro workspace. Sign in to open the calculator, run unlimited sizing checks, and export permit-ready documentation.
Joist spans come from IRC Table R507.6, beam spans from Tables R507.5(1)–(4), and ledger fastener spacing from Table R507.9.1.3(1) — the same tables your building inspector checks against. Where a configuration falls outside the prescriptive tables, the tool tells you so and routes you to a design review instead of guessing.
Most span calculators ignore engineered lumber. The Deck Sizer includes HI-Clear II Treated Douglas Fir Glulam — which carries full, unreduced design values — and Canfor/Anthony Pressure-Treated Southern Yellow Pine Glulam as first-class beam options, alongside treated dimensional lumber and LVL. It also supports the LVL rim ledger detail grounded in AWC DCA-6 Commentary C9.
Choose your jurisdiction — St. Louis, St. Charles, O’Fallon, or Wentzville — and the tool applies the right IRC edition and local amendments, including Wentzville’s cantilever prohibition. Planning a deck elsewhere? The IRC 2021 defaults apply nationwide.
Results from this calculator are preliminary sizing guidance for comparison and planning. They are not engineering, not sealed drawings, and not a substitute for design by a licensed professional under your local code. Final member sizing, connections, and load paths must be confirmed for your specific project.
Bardowl Design produces structural layouts and material specifications that builders and lumberyards can actually work from. Clear scope, defined assumptions, documented output.
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