(a) The following projections beyond street or alley lines and encroachments upon public property are specifically prohibited.
(1) Steps which are not contained within permitted base courses;
(2) Steps which project beyond the permitted projection of base courses;
(3) Areas for light and ventilation of below- grade rooms or spaces;
(4) The projection of doors when opening or opened in a horizontal direction;
(5) Storm doors and enclosures;
(6) Fire escapes, fire tower balconies, balconies serving as horizontal exists, or other similar means of egress, except when specifically approved by the Board of Building Standards and Building Appeals;
(7) Under-grade uses prohibited by Section 3109.20.
(b) Sidewalks shall not be used for the display of goods, wares or merchandise, or for other similar commercial purpose.
(c) The prohibitions of this section shall not be interpreted as permitting the construction of any projections or encroachments not specifically permitted by this Building Code.