Every part of a required yard shall be open and unobstructed to the sky, except for accessory buildings in a rear or side yard, and except for the ordinary projections of skylights, sills, beltcourses, cornices, and ornamental features projecting not more than one (1) foot. This requirement shall not prevent the construction of fences not more than six (6) feet in height except on that portion of a lot(s) within thirty (30) feet of the intersection of two (2) or more streets. Terraces, uncovered porches, patios, plat forms and ornamental features which do not extend more than three (3) feet above the level of the ground (first) story may project into a required side or rear yard, provided these projections are at least two (2) feet from the adjacent lot line. The ordinary projections of chimneys or flues are permitted into the required side, rear and front yards. An open, unenclosed porch or paved terrace may project into the front yard not more than ten (10) feet.