2013 California Standards for Accessible Design Pocket Guide

4.      Reinforced walls for grab bars.   Grab bar reinforcement shall be installed continuous in the walls of showers 32 inches to 38 inches (813 mm to 965 mm) above the floor. The grab bar reinforcement shall be a minimum of 6 inches (152.4 mm) nominal in height.

       Glass-walled shower stalls shall provide reinforcement for installation of floor-mounted or ceiling-mounted grab bars.