The following uses and structures constitute obstructions which are nevertheless permitted in any required yard area:
(a) Awnings and canopies;
(b) Window air conditioners;
(c) Chimneys which project no more than three feet into a rear yard;
(d) Eaves, gutters or downspouts which project no more than sixteen inches into a yard;
(e) Flagpoles;
(f) Walls or fences, as regulated for type and height;
(g) Steps, excluding fire escapes; and
(h) Off-street parking areas which are not covered by a structure.