Any nonconforming building, structure or use may be changed to conform to this chapter, but shall not be changed back to a nonconforming status.

No existing building or premises devoted to a nonconforming use as permitted by this section shall be enlarged, extended, reconstructed or structurally altered unless such use is changed to a use permitted in the district in which such building or premises is located; and no nonconforming use shall be changed to another or different nonconforming use.

Notwithstanding the above, a one- or two-family dwelling and its accessory uses existing in a residential district may be expanded or enlarged, provided that such expansion or enlargement complies with all zoning ordinance requirements for a one- or two-family dwelling and accessory uses in the residential zoning districts.

No nonconforming use or structure which shall have been discontinued or abandoned for a period exceeding 12 months shall be resumed; provided, however, that no such use or structure shall be resumed if the premises upon which such use or structure existed is devoted to a conforming use after the discontinuance or abandonment of the nonconforming use.

A nonconforming use shall be considered abandoned if it is terminated by the owner; if a nonconforming use involving a building or structure is discontinued for a period of 12 consecutive months; or if a nonconforming use of land not involving a building or structure is discontinued for a period of six months. The subsequent use of the abandoned building, structure and/or land shall be in conformity with this chapter.

Any nonconforming use or structure existing on the effective date of this chapter may be restored or repaired in the event of partial destruction thereof, provided that the cost of such restoration and repair in compliance with all the existing construction codes of the Borough of Oakland does not exceed 50% of the market value of the structure, less foundation systems, at the time of the partial destruction.

If the value of repairing the condition is greater than 50% of the value of replacing the entire structure, it shall be considered completely destroyed and may be rebuilt to the original specifications only upon approval of a use variance as provided under Article V of this chapter and as further provided by state statute.

In the event of a partial destruction of a structure devoted to a nonconforming use, the owner or occupant shall, within 90 days after such event, give notice in writing to the Zoning Enforcement Official of his intention to restore or repair the structure and, within 90 days after date of notice, commence and diligently proceed to the completion of the work. In such event, the nonconforming structure or use may be rebuilt and used for the same purpose as before, provided that it does not exceed the height, area and volume of the original structure.

The percent damaged shall be the current replacement cost of the portion damaged and condemned, computed as a percentage of the current total replacement cost of the entire structure, neither to include the cost of the foundation.

Repairs and maintenance may be made to a nonconforming use, structure or lot, provided that the repair and maintenance work do not change the use, expand the building or the functional use of the building, increase the area of a lot used for a nonconforming purpose or increase the nonconformity in any manner.

Nothing contained in this section shall prohibit the modernization of existing nonconforming structures; provided, however, that such modernization does not entail any extension, enlargement, addition or change of the nonconforming use.