Stair riser ≤ 8¼ in, tread depth ≥ 9 in (NY-amended — steeper than the base IRC)
2025 RCNYS §R318.7.5.1 / R318.7.5.2 Stair riser + tread (NY-amended)Description
Risers must be at most 8¼ in tall, measured between leading edges of adjacent treads. The greatest riser in any flight must not exceed the smallest by more than 3/8 in. Treads must be at least 9 in deep, measured horizontally between vertical planes of the foremost projection of adjacent treads. Variation across treads in one flight: no more than 3/8 in. Open-riser openings ≥ 30 in above floor must not pass a 4-in sphere. Winder treads: ≥ 10 in at the walkline, ≥ 6 in at any point.
Why this exists
NY's 8¼ in riser / 9 in tread is STEEPER than the IRC-base 7¾ × 10 in. This single difference rejects most stock stair-design assumptions made from generic IRC references. Architects working in NY must size stair runs against the NY geometry — a 14-tread run at 7¾ × 10 lands at one length; the same vertical at 8¼ × 9 lands at a meaningfully shorter run.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxRiser | max | 8.25 | in | Stair riser maximum height |
minTread | min | 9 | in | Stair tread minimum depth |
variationTolerance | max | 0.375 | in | Variation across treads/risers in one flight |
winderWalkline | min | 10 | in | Winder tread depth at walkline |
openRiserSphere | max | 4 | in | Maximum sphere passing open-riser opening (>30 in above floor) |
Categories
Applies to
- Jurisdiction: New York State
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.
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 2026-05-15.