(a) For a building devoted in whole or in part to a nonconforming use, work may be done in any period of twelve (12) consecutive months to complete ordinary repairs, or on the repair or replacement of nonbearing walls, fixtures, wiring or plumbing to an extent not exceeding fifty (50) percent of the assessed value of the building, provided that the cubic content of the building, as it existed at the time of passage or amendment of this Zoning Ordinance, is not increased.
(b) Nothing in this Zoning Ordinance shall be deemed to prevent the strengthening or restoring to a safe condition, a building, or part thereof, declared to be unsafe by an official charged with protecting the public safety, upon the order of such official.