Deck Ledger Load Calculator
Line load on a deck ledger and the lag/bolt spacing it demands.
Half the deck hangs on the ledger. Most catastrophic deck collapses are ledger pull-offs — through-bolts with washers beat lags, and flashing beats both (rot kills more ledgers than load).
Formula
Deck Ledger Load Calculator is a free deck ledger for structural engineers, fabricators and site engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Deck Ledger Load Calculator
Line load on a deck ledger and the lag/bolt spacing it demands. The calculation implements w = q·(joist span)/2; s = capacity/w (IRC R507.9; DCA 6 deck guide). Half the deck hangs on the ledger. Most catastrophic deck collapses are ledger pull-offs — through-bolts with washers beat lags, and flashing beats both (rot kills more ledgers than load).
How to use Deck Ledger Load Calculator
- 1Enter Deck joist span (out from ledger) in m.
- 2Enter Deck design load in kN/m² (Residential deck: 1.6 DL + 2.0 LL ≈ 3.6).
- 3Enter Fastener design capacity in kN (½" lag in seasoned timber ≈ 1.5–2 kN shear).
- 4Read Ledger line load, Max fastener spacing instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Deck Ledger Load Calculator?
- ✓Implements the standard formula — w = q·(joist span)/2; s = capacity/w
- ✓Reference cited on-page: IRC R507.9; DCA 6 deck guide
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Deck Ledger Load Calculator use?+
It computes w = q·(joist span)/2; s = capacity/w, per IRC R507.9; DCA 6 deck guide. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Half the deck hangs on the ledger. Most catastrophic deck collapses are ledger pull-offs — through-bolts with washers beat lags, and flashing beats both (rot kills more ledgers than load).
Can I use this for real structural design?+
It implements the exact textbook/code formula cited below the result and is ideal for sizing, checking and learning. Final designs should be verified by a qualified engineer against the full code with all load cases.
Is the Deck Ledger Load Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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