2016 California Standards for Accessible Design Pocket Guide - Eff. Jan. 1, 2017

11B-306.3.1 General.

Space under an element between 9 inches (229 mm) and 27 inches (686 mm) above the finish floor or ground shall be considered knee clearance and shall comply with Section 11B-306.3. 

Exception:  At lavatories required to be accessible by Section 11B-213.3.4, space between 9 inches (229 mm) and 29 inches (737 mm) above the finish floor or ground, shall be considered knee clearance.