The provisions of this chapter shall apply to all new development on each lot or site upon application for a building permit, except for the following:
1. Reconstruction or replacement of a lawfully existing use or structure following a casualty loss.
2. Remodeling, rehabilitation, or improvements to existing uses or structures which do not substantially change the location of structures, parking, or other site improvements.
3. Additions or enlargements of existing uses or structures which increase floor area or impervious coverage area by less than 20 percent of the building established on the site on the effective date of this ordinance. Where such cumulative additions or enlargements are 20 percent or greater, these provisions shall apply only to that portion where the new development occurs.