Deck Ledger Fastener Spacing (IRC R507.9)
On-center spacing, fasteners for the ledger length, and a span/table check.
Example
You enter
- Joist span (ft) 12
- On-center spacing (in, from IRC table) 16
- Ledger length (ft) 16
- Fastener type lag
You get
- Fasteners for ledger 13
- On-center spacing 16 in OC
Details, formula, and sources
Per IRC R507.9; the spacing is user-supplied from the adopted table for the fastener/span row.
Fastener count = floor(ledger_length_ft x 12 / on-center spacing) + 1; spans <= 18 ft are within the IRC table, beyond require an engineered connection.
IRC §R507.9 deck ledger connection provisions, by name.
Free read-only at codes.iccsafe.org; the AHJ-adopted edition governs.
Estimate. AHJ and licensed structural engineer govern.
Field names used by the API: joist_span_ft, spacing_in, ledger_length_ft, fastener, fastener_count
- Spacing user-supplied from the adopted IRC R507.9 table; bolt edge-distance and stagger apply; bottom-of-ledger spacing excludedIRC R507.9