In addition to all applicable setback restrictions, no accessory structure shall be placed on any lot between the principal building and the front lot line, or between the principal building and any side lot line abutting any street. For the purpose of this subsection, the “principal building” shall be deemed to include not only the physical structure, but also a line from that point on the structure closest to the relevant front or side lot line and parallel to such front or side lot line across the width of the lot.