| Primary value | 250 mm |
| Applies to | Single-family houses · Apartment internal stairs |
| Exceptions | Assembly / educational / commercial → 300 mm min |
| Measured as | Horizontal depth of the tread from riser face to nosing, excluding any nosing overhang. |
| Source | NBC 2016 — Part 4, Clause 4.4.2 ✓ Verified |
13 related items across IS codes, knowledge articles, design rules, maps and tools
250 mm is the smallest depth on which an adult foot can land securely while descending. Below this, descent becomes hazardous because the heel doesn't have a stable platform.
Comfortable residential stairs use 275–300 mm treads. Below 250 mm feels tight; above 300 mm requires more horizontal space than tight Indian apartments allow.