Except as provided in §§ 169-77 and 169-78 of this chapter, any use of land or a building or structure or part thereof lawfully existing at the time that this chapter or any amendment thereto becomes effective may be continued, subject to the provisions of §§ 169-79 through 169-83 of this chapter, although such building or structure or use does not conform to the provisions of the district in which it is situated. No unlawful use of property or unlawful building or structure existing on the effective date of this chapter shall be deemed a nonconforming use, structure or building.

When a nonconforming use has been discontinued for a period of one year, it shall not thereafter be reestablished, and the future use shall be in conformity with the provisions of this chapter.

Notwithstanding any other provision of this chapter, any nonconforming billboard, sign or advertising device in existence in any residential district on the effective date of this chapter or an amendment thereto shall be discontinued within three years from the effective date of such adoption or amendment. See Chapter 138, Signs and Billboards.

No nonconforming use shall be changed to any use other than a conforming use for the district in which it is situated.

Alterations and extensions of a nonconforming use, in order to comply with the provisions of this section, are permitted, provided that such alterations or extensions shall not tend to increase an inherent nuisance nor shall such alterations or extensions violate any provisions of this chapter regarding yards, lot area or lot coverage for the district in which the use is situated or to increase any existing violation of such provisions.

Except as otherwise heretofore set forth, no building or structure designed for or intended to be utilized for a nonconforming use shall be constructed, reconstructed or altered unless construction, reconstruction or alteration is already underway on the effective date of the enactment of this chapter and is being diligently pursued so that such building or structure will be completed within 18 months from the effective date of this chapter. All outstanding building permits for construction, reconstruction or alteration which do not meet these requirements shall be rendered null and void by the enactment of this chapter.

The limitations of §§ 169-81 and 169-82 hereof shall not apply to a building or other structure utilized as a dwelling or accessory thereto which is nonconforming only in respect to yard space or land area per dwelling and nonconforming to the district in which located, except no building shall be altered, added to or reconstructed to extend further into an already deficient yard space or to reduce an already deficient amount of land area per dwelling.