Any structure, for which construction was begun prior to the effective date of this chapter, or of any amendment thereto, may be completed and used in accordance with the approved plans and specification for such structure. Any structure for which construction has not begun pursuant to approved plans shall be subject to the provisions of this chapter and any amendments thereto, even if all preconstruction approvals have been granted. For purposes of this section, "beginning construction" shall mean excavation and the pouring of footings or the installation of any other means of permanently attaching a structure to the ground.