Protection of basement and cellars. Every multiple dwelling of class “b” having 20 or more sleeping rooms and exceeding 2 stories in height and having a basement or cellar, the floor above which is not of fireproof construction, shall have its basement or cellar ceiling protected with metal lath and 3/4 of an inch of portland cement or gypsum plaster, or the basement or cellar shall be protected with an approved automatic sprinkler system or an approved and self supervised and properly maintained automatic fire alarm system. The floor of the cellar or lowest floor of every dwelling shall be free from dampness, and, when necessary in the judgment of the health officer or such other appropriate public official as the mayor may designate, shall be concreted with not less than 3 inches of concrete of good quality and with a finished surface.