Any lawful building, structure or use of premises existing at the effective date of the original zoning law of the city, as approved by the Olean Common Council on July 28, 1936, or any subsequent amendment thereof applying to such building, structure, or use of premises, may be continued although such building, structure, or use of premises does not conform to the provisions of this law provided however:
12.0.1 Nothing herein contained shall be construed to render lawful any use not lawfully conforming to provisions of the city's zoning law hereby repealed.
12.0.2 Any extension of a non-conforming use must conform to the provisions of this law.
12.0.3 No non-conforming building or structure shall be enlarged, extended or increased during its life to an extent exceeding 15% of its existing gross floor area or in aggregate value 50% of the replacement cost of the building, whichever is greater, unless said building or structure is changed to conform to the requirements of this law.
12.0.4 A building or structure containing a non-conforming use may be repaired or strengthened sufficiently to remove a hazard to public safety, as such hazard may be determined by the code enforcement officer, but not so as to perpetuate the non-conforming use or character of the structure. Nothing in this law shall prevent the strengthening or restoring to a safe condition any wall, floor or roof which has been declared unsafe by the code enforcement officer.
12.0.5 Only by approval of the zoning board of appeals shall a building used to house a non-conforming use be restored if damaged or destroyed by fire, flood, earthquake or other act of God. Substantial restoration shall be made within six months of the occurrence of the damage, except that this time limit may be extended by the zoning board of appeals in cases of practical difficulty or hardship. Any building damaged by such occurrence to the extent of more than 50% of its replacement value and not demolished shall be repaired or rebuilt within a six-month period to conform to the building line of the original structure.
12.0.6 No non-conforming use shall be maintained, renewed, changed or extended without a certificate of compliance having first been issued by the code enforcement officer.