(A) Any lawful building, structure, or use existing at the time of the enactment of this chapter may be continued, even though such building, structure, or use does not conform to the provisions of this chapter for the district in which it is located, and whenever a district shall be changed hereafter, the then existing lawful use may be continued (subject to the provisions of §§ 156.140 et seq.).
(B) Any legal non-conforming building or structure may be continued in use provided there is no physical change other than normal maintenance and repairs, except as otherwise permitted herein.
(C) Any building for which a permit has been lawfully granted prior to the effective date of this chapter, or of amendments hereto, may be completed in accordance with the approved plans, provided construction is started within 90 days and diligently prosecuted to completion. Such buildings shall be thereafter deemed to be a lawfully established building.
(`92 Code, § 40-6-1)