a. Every building containing rooming units, and each individual apartment used for single room occupancy, shall contain at least one water closet, washbasin and bath or shower for each six persons lawfully occupying rooming units therein, and for any remainder of less than six persons. At least one water closet shall be located on any floor containing a rooming unit. If there are not more than two rooms on the first story above the basement in said rooming house, no water closet is required on such floor but the occupants of the room shall be counted in determining the required number of facilities.
b. Every occupant of a rooming unit shall have access to each required water closet, washbasin and bath or shower without passing through any other rooming unit or portion of the dwelling reserved for other occupants.
c. Any additional water closet installed to comply with the requirements of subdivision a of this section shall be located in a compartment, separate from any other water closet, bath or shower, except that a required washbasin may be provided in such compartment. Such additional baths, or showers, shall be located in compartments separate from every required water closet.
d. Sanitary facilities for the exclusive use of and accessible only to the occupants of one rooming unit may be combined in a bathroom. Neither the facilities nor the occupants shall be counted in determining the number of the facilities required in subdivision a of this section.