Any use which is made a nonconforming use by this chapter or by any subsequent amendments thereof may be continued, except as hereafter provided.

Unless otherwise provided in this article, a nonconforming use shall not be enlarged or extended, except that in any C or M District any nonconforming use within a building may be enlarged to an extent not exceeding 25% in the aggregate of the gross floor area devoted to such nonconforming use. In no case shall enlargement extend beyond the lot occupied by such nonconforming use or violate any height, yard, parking area or other open space requirement of this chapter. When the total of all enlargements equals 25% of the gross floor area existing at the time such use became a nonconforming use, no further enlargements shall be permitted.

Unless granted a variance by the Concord Zoning Board of Appeals, no building or structure containing a nonconforming use which has been damaged by fire or other causes to the extent of 50% or more of its equalized assessed value, as determined by the Town Assessor of the Town of Concord, shall be rebuilt or repaired except in conformance with the regulations of this chapter. In such reconstruction, neither the gross floor area nor the cubical content of a nonconforming use shall be increased from the floor area or cubical content of the nonconforming use prior to the time of damage.

In any district, whenever a nonconforming use of land, premises, building or structure has been discontinued for a period of one year, such nonconforming use shall not thereafter be reestablished, and all future use shall be in conformity with the provisions of this chapter. Such discontinuance of the active and continuous operation of such nonconforming use for such period of one year is hereby construed and considered to be an abandonment of such nonconforming use, regardless of any reservation of an intent not to abandon the same or of an intent to resume active operations. If actual abandonment in fact is evidenced by the removal of buildings, structures, machinery, equipment and other evidences of such nonconforming use of the land and premises, the abandonment shall be construed and considered to be completed within a period of less than one year, and all rights to reestablish or continue such nonconforming use shall thereupon terminate. The provisions of this section shall not apply to agricultural lands participating in federal or state agricultural programs, nor shall they be construed to interfere with normal agricultural practices of crop rotation.