It is unlawful to build, erect, establish or maintain at any place on any sidewalk within the city any trapdoor, swinging, sliding or hinged door, scuttle hole, iron grating, opening for stairway where the same extends in whole or in part upon or across any part of the sidewalk, whether the same is enclosed or unenclosed, or any opening of any kind whatsoever leading or opening through such sidewalk to or into any basement, cellar or excavation; provided, that, the provisions of this section shall not apply to the maintenance, remodeling or enlarging of any opening already constructed and now a part of an appurtenance of any building or basement thereof, such remodeling and enlarging to be done under the direction of the chief of the fire department. (Prior code § 27-50)