Stair riser, tread, and headroom
IRC R311.7Description
Stairs must have a riser height of 7-3/4 inches maximum, tread depth of 10 inches minimum, and headroom of 6'8" (80 inches) minimum measured vertically from the nose of each tread.
Why this exists
These dimensions are the minimum that lets an adult use the stairs without ducking and without missing treads in low light. Older homes built to looser standards regularly produce stair-fall injuries — IRC tightened these in 2012 and again in 2018.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxRiserHeight | max | 7.75 | in | Maximum riser height (7-3/4 inches). |
minTreadDepth | min | 10 | in | Minimum tread depth (10 inches). |
minHeadroom | min | 80 | in | Minimum vertical headroom from nosing (6'8"). |
Categories
Source
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.
Plan symbols this applies to
These plan symbols invoke this directive when placed on a floor plan. Click any to see where it's drawn and what other rules apply to it.
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
- Smoke alarms required throughout dwelling · IRC R314
- Carbon monoxide alarms in sleeping areas · IRC R315
Last reviewed 2026-05-09.