A zoning permit shall be secured from the Zoning Officer prior to construction, reconstruction, erection or alteration of any building, structure or portion thereof, any change in the use of a building or land, and prior to the change or extension of a legal nonconforming use. However, a zoning permit shall not be required for the following:
A. Alteration of an existing building not involving any exterior addition thereto. However, a building permit shall be secured from the Building Inspector for this purpose prior to commencing such an alteration.
B. Farm buildings situated 50 feet or more from any street or property line, but all such farm buildings shall be erected in conformity with the use, area and height regulations applicable in the district in which such farm buildings are located.