CodeMandatory
Stair walkline
IRC R311.7.3Description
The walkline used for tread-depth measurement is 12" from the inside edge of the stair, where occupants actually step.
Why this exists
On winder stairs, treads can be wedge-shaped. The walkline rule fixes where the tread depth must be ≥10".
Categories
Life safetyCirculation
Source
ICCno manifest entry
International Residential Code (2024)
Section: R311.7.3
Published 2024-01-01 · last verified 2026-05-09
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Garage / dwelling fire separation · IRC R302.6
- Habitable space minimum ceiling height · IRC R305.1
- Egress window net opening dimensions · IRC R310.2
- Stair riser, tread, and headroom · IRC R311.7
- Smoke alarms required throughout dwelling · IRC R314
Last reviewed 2026-05-09.