(a) A lawfully established use of a building or land established prior to the adoption of this Zoning Code that does not conform to the use regulations for the district in which it is located, shall be deemed a legal nonconforming use and may be continued, except as provided in this chapter.
(b) A legal nonconforming building or structure may be continued in use provided there is no physical change other than necessary maintenance and repair, except as otherwise permitted in this chapter.
(c) A building for which a permit has been lawfully granted prior to the effective date of this Zoning Code, or of an amendment thereto, may be completed in accordance with the approved plans if the construction is started within six months after the date of the permit and diligently prosecuted to completion. Such building shall, thereafter, be deemed a lawfully established building.