The following rules shall apply to building projections into required yards:
(a) An enclosed balcony, fire escape, unenclosed and uncovered porch or metal awning may project into a required front or rear yard for a distance not exceeding ten feet, and into a required side yard not exceeding three feet.
(b) Sills, belt courses, cornices, eaves and ornamental features may project into required yards for a distance not exceeding twelve inches.
(c) An enclosed vestibule containing not more than forty square feet may project into a front yard for a distance not exceeding four feet.