Any lawful structures, building or use of a building or premises or part thereof at the time this chapter or any amendment thereto is adopted may be continued although such structure, building or use does not conform to the provisions thereof, provided that such structure or building has not been abandoned or such use discontinued for a period of 2 years or more.

No building which has been damaged by fire or other causes to the extent of more than 3/4 of its fair market value shall be repaired or rebuilt except in conformity with this chapter.

The Board of Appeals may permit any nonconforming use of a building or land to be changed to any other nonconforming use not substantially different in character or more detrimental or objectionable to a neighborhood or, if in a part of a building designed or intended for such use, extended throughout such building.

The Board of Appeals may permit a nonconforming temporary building or use incidental to the development of a neighborhood, such permit to be issued for an initial period of not more than 2 years. Such permits may be renewed by the Board for successive periods of not more than 1 year each.

The record owner of any land may waive the provisions of this article at any time by filing a duly recorded instrument with the Registry of Deeds, in which case the bylaw then or thereafter in effect shall apply.