Accessory off-street parking spaces shall be permitted for dwelling units in non-residential buildings erected prior to January 1, 1977, or portions thereof, that are converted to residential use, provided:

(a)        no more than 200 spaces or a number of spaces equal to 20 percent of the number of dwelling units in the converted building, whichever is less, shall be permitted;

(b)        no curb cut shall be permitted on any street where the converted building has a street frontage of 40 feet or less;

(c)        no portion of any such parking facility shall be more than 23 feet above curb level;

(d)        no exhaust vents shall open onto any street or public park or publicly accessible open space, and no portion of the parking facility, other than entrances and exits, shall be visible from adjoining zoning lots, streets or parks; and

(e)        all such parking facilities shall be provided on the same zoning lot as the residential uses to which they are accessory, except as otherwise provided in Section 91-511 (Authorization for off-site parking facilities for converted buildings).