Nothing contained in this Zoning Ordinance shall require any change in the overall layout, plans, construction, size or designated use of any building or part thereof, for which approvals and required building permits have been granted before the enactment of the Zoning Ordinance, the construction of which in conformance with such plans has been started prior to the effective date of the Zoning Ordinance, and completion thereof has been carried on in a normal manner and not discontinued for reasons other than those beyond the builder’s control.