2013 California Standards for Accessible Design Pocket Guide

11B-504.2 Treads and risers.

All steps on a flight of stairs shall have uniform riser heights and uniform tread depths. Risers shall be 4 inches (102 mm) high minimum and 7 inches (178 mm) high maximum. Treads shall be 11 inches (279 mm) deep minimum.

Exception:  Curved stairways with winder treads are permitted at stairs which are not part of a required means of egress.