Unless otherwise restricted by application of regulations in Section 415.240, Air Navigation Space Regulations, the total height of any structure other than a wireless support structure, disguised support structure or substantial modification thereof subject to Chapter 430 of the City Code, including roof top mechanical equipment attached to such structure, shall not exceed two (2) stories or forty (40) feet in height, whichever is less, above the average finished ground elevation at the perimeter of such structure unless authorized by conditional use permit.