The following types of nonconforming uses may be continued, and upon the obtaining of a permit from the Board of Appeals as provided in § 200-65G, any such use may be enlarged to an aggregate extent of not to exceed 25% of the area of land occupied by such use or the floor area of the building in which such use is conducted but not so as to exceed the maximum building area, floor area or floor area ratio prescribed for the district; provided, however, that the total value of all alterations made in any such building shall at no time exceed 50% of its value at the date of nonconformity:
A. 
A use permitted in a C District of one class either with or without a permit from the Board of Appeals and existing as a nonconforming use in a C District of another class.
The following types of nonconforming uses may be continued, but shall not be enlarged or extended, nor shall any structural alterations be made in any building in which any such use is conducted:
A. 
A use permitted in an R District of one class and existing as a nonconforming use in an R District of another class.
B. 
A multifamily dwelling existing as a nonconforming use in a C or I District.
C. 
An office use permitted in a C-1 District and existing as a nonconforming use in an R District.
D. 
A nonconforming use in an I District, provided that any junkyard that is not completely enclosed within walls or a fence approved by the Board of Appeals as provided in § 200-67C shall, within two years after the adoption of this chapter, be so enclosed or be discontinued and removed or changed to a conforming use.
Any other nonconforming use shall be discontinued and removed or changed to a conforming use within a period of five years from and after the date of the adoption of this chapter.
A nonconforming building or a building in which a non-conforming use is conducted that is destroyed or damaged by any casualty to an extent not exceeding 50% of its value, exclusive of foundations, at the time of such destruction or damage, may be restored within one year after such destruction or damage, but shall not be enlarged except as provided in § 200-75. If any such building is so destroyed or damaged to an extent exceeding 50% of its value as above, it shall not be reconstructed except as a conforming building and for a conforming use; provided that any non-conforming building used as a one-family dwelling that is so destroyed or damaged to an extent exceeding 50% of its value may be reconstructed within one year after such destruction or damage so as to occupy the same space that it occupied prior to such destruction or damage, or any part thereof.
Nothing in this Article shall be deemed to prevent keeping in good repair a building in which a nonconforming use is conducted.
If any nonconforming use ceases for a continuous period of one year or more or is changed to or replaced by a conforming use, the land and building theretofore devoted to such nonconforming use shall thereupon be subject to all the regulations as to use for the district in which such land and building are located as if such nonconforming use had never existed.
Any use for the establishment of which a permit from the Board of Appeals is required under the use regulations for a particular district as set forth in Article V, whether such use is existing in such district at the time of the adoption of this chapter or is subsequently established therein on the obtaining of such permit, shall be deemed to be a conforming use in such district; provided that any subsequent replacement or enlargement of such use or of any building in which the same is conducted or the construction of any additional building for such use beyond the extent specified in any such permit shall be subject to the obtaining of a further permit therefor from the Board of Appeals.
The foregoing provisions shall apply to all nonconforming uses existing at the time of the adoption of this chapter and to all uses that become nonconforming by reason of any amendment thereof, but not to any use that is established in violation of law.