Extension or enlargement. The nonconforming use of a building or of a lot shall not be extended or structurally enlarged so as to use other portions of the building or lot, except insofar as is permitted by law to assure the structural safety of a structure, unless the Zoning Hearing Board shall, by special exception as hereinafter provided, authorize the extension or enlargement of such use or building. The Zoning Hearing Board, upon proper application, may grant such special exception, provided that:
(1) It is clear that such extension is not materially detrimental to the character of the surrounding area or to the interest of the City.
(2) The area devoted to the nonconforming use shall not be increased by more than a total of 10%. This increase shall occur only once during the life of a nonconforming use.
(3) Any extension or enlargement of the building or of a lot having a nonconforming use shall conform to all applicable area and bulk regulations of the district in which it is situated and to all regulations applicable to such a use in the City.