CodeMandatory
Stair tread depth minimum 9 inches
Virginia USBC 2021 Amendment 20 (IRC R311.7.5.2)Description
The tread depth shall be not less than 9 inches. The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at right angles to the tread's leading edge.
Why this exists
Less than the IRC's 10" baseline. Combined with the 8.25" riser, Virginia's residential stair is steeper than other adoptions. Designers should still target the IRC 10"+7.75" geometry where space permits.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
minTread | min | 9 | in | Minimum tread depth |
Categories
Life safetyCirculation
Applies to
- Jurisdiction: Virginia
Source
Virginia DHCDauthoritative
2021 Virginia Construction Code (Part I of USBC) (2021)
Section: Amendment 20 (IRC R311.7.5.2)
Published 2024-01-18 · last verified 2026-05-10
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 2026-05-10.