For all buildings located on lots with frontage on Colorado Avenue, minimum height of the lowest finished ceiling including intermediate floors such as mezzanines and balconies above sidewalk grade shall be not less than eleven and three-quarters feet (11.75') measured from the average sidewalk grade along the building frontage to the bottom of the ceiling, such minimum to apply within an area extending into the building a distance of twenty-five (25) feet from the Colorado Avenue property line.