Sill-Plate Anchor Bolt Count (IRC R403.1.6)
Lays out sill-plate anchor bolts at the IRC max spacing with a bolt near each end.
Example
You enter
- Wall / plate length (ft) 40
- Maximum anchor spacing (ft) 6
- Bolt distance from each end (in) 9
You get
- Span between end bolts 38.5 ft
- Anchor bolts 8
Details, formula, and sources
bolts = max(2, ceil((wall - 2 x end distance) / max spacing) + 1). A 40 ft wall at 6 ft spacing with 9 in end distances takes 8 bolts; a short 8 ft wall still needs 3 because the 6.5 ft between end bolts exceeds the 6 ft spacing - a mid bolt the two-bolt minimum alone would miss. IRC R403.1.6 caps spacing at 6 ft; the code and engineered plan govern. Distinct from anchor-embedment capacity.
effective_len_ft = wall_length_ft - 2 x (end_distance_in/12); bolts = max(2, ceil(effective_len_ft / max_spacing_ft) + 1).
Sill-plate anchor-count rule by name (bolts from the span between end bolts over the max spacing, min two); IRC R403.1.6.
The anchor-count layout is public IRC R403.1.6 prescriptive geometry; the adopted code edition and any engineered plan govern.
Estimate. AHJ and licensed professional govern.
Field names used by the API: wall_length_ft, max_spacing_ft, end_distance_in, effective_len_ft, bolts
- Max spacing 6 ft per IRC R403.1.6; high-wind/seismic or engineered plans tighten itIRC R403.1.6
- End distance a bolt within 12 in of each end and corner; minimum two bolts per plateIRC R403.1.6