(c) Additional required water-closets and wash basins which are installed in order to comply with the provisions of this paragraph whether provided separately or in combination, shall be in a compartment separate and apart from every bath or shower required under the provisions of paragraph b, and each such additional required bath or shower shall be in a compartment separate and apart from every water-closet and wash basin required under the provisions of paragraph b, except that any such additional required water-closet, bath or shower or wash basin may be included in a single compartment containing any or all of such facilities, if such compartment is accessible only from or only within a room, apartment or suite of rooms and the occupant or occupants of such room, apartment or suite are exclusively entitled to use all such facilities contained in such compartment. 5. Old-law tenements. In every old-law tenement there shall be provided for the exclusive use of each family at least one water-closet compartment located within the dwelling. Such compartment shall be constructed and ventilated as approved by the department but such compartment shall be located on the same story as that on which the apartment occupied by each such family is situated and shall be equipped with lock and key. The provisions of this subdivision shall not apply (a) to any dwelling which the department of city planning certifies is in an area to be acquired for a public improvement and for which a request for acquisition has been submitted to the board of estimate by a public agency; or (b) to any dwelling in an area for which an urban renewal plan has been submitted to the planning commission, as provided in section five hundred five of the general municipal law, if the planning commission shall certify that compliance with the provisions of this subdivision would be inconsistent with the plan; or (c) for which a demolition permit has been or shall be issued by the municipality pursuant to local law or ordinance. The exemption provided in (a), (b), and (c) of this subdivision shall be valid for a period of six months after the date of the acquisition request or the date of the submission of the urban renewal plan to the commission or the date of the issuance of the demolition permit as the case may be. Such exemption may be extended from time to time by the department provided, however, that such exemption shall not extend beyond November first, nineteen hundred sixty-five. 6. Single room occupancy. a. Every apartment used for single room occupancy shall have at least one bath or shower, one wash-basin and one water-closet for each six adult persons who may lawfully occupy the rooms in such apartment as provided in section two hundred forty-eight, and for any remainder of less than six persons. If additional baths or showers or water-closets are installed within an apartment in order to comply with the provisions of this paragraph each water-closet shall be in an enclosure separate and apart from every bathroom or shower room and each bath or shower shall be in an enclosure separate and apart from every water-closet. b. There shall be access to each required water-closet and bathroom without passing through any sleeping room, except that any water-closet, wash-basin or bathroom which connects directly with any sleeping room shall be deemed to be available only to the occupants of such room and shall not be included in the computations for the required number of water-closets and bathrooms. 7. Saving clause. No change need be made in the number, construction, arrangement, lighting or ventilation of water-closet compartments, bathrooms or general toilet rooms in any portion of any dwelling if the number, construction, arrangement, lighting or ventilation of such water-closet compartments, bathrooms or general toilet rooms was lawful on July first, nineteen hundred sixty-one.