All cellars or spaces beneath the first floor or basement of any building of the grades referred to in this act shall be damp-proof and water-proof, and when, in the opinion of the Chief of the Division of Housing and Sanitation, conditions require it, they shall be concreted with good concrete and a finished surface to a depth of not less than four inches, and the walls shall be coated with the same or other nonpermeable surfacing to such depth as to prevent the incoming of water.