All nonconforming uses or structures not designated Class A shall be Class B nonconforming uses or structures. Class B nonconforming uses and structures shall comply with all the provisions of this article relative to nonconforming uses and structures.

Nonconforming uses or structures shall be designated Class A, providing that the Planning Commission finds all of the following exist with respect to the use or structure:

The decision to grant a Class A designation shall be made, in writing, setting forth its findings of fact and basis for the designation. For changes or improvements to a Class A use or structure, site plans shall be required and the Planning Commission may condition its approval on the following, and by the following procedure to ensure the public health, safety or welfare or the spirit and purpose of this chapter:

In any district in which single-family dwellings are permitted, notwithstanding limitations imposed by other provisions of this chapter, a single-family dwelling and customary accessory buildings may be erected on any single lot of record recorded with the Register of Deeds at or before the effective date of adoption or amendment of this chapter. This provision shall apply even though such lot fails to meet the requirements for area or width, or both, that are generally applicable in the district; provided that yard dimensions, setbacks and other requirements not involving area or width, or both, of the lot shall conform to the regulations for the district in which such lot is located, unless a yard requirement variance is obtained through approval of the Zoning Board of Appeals. However, if two or more lots or combinations of lots and portions of lots with continuous frontage in single ownership are of record at the time of passage or amendment of this chapter, and if all or part of the lots do not meet the requirements established for lot width and area, the lands involved shall be considered to be an undivided parcel for the purposes of this chapter, and no portion of said parcel shall be used or divided in a manner which diminishes compliance with lot width and area requirements established by this chapter.

Where, at the effective date of adoption or amendment of this chapter, a lawful use of land exists that is made no longer permissible under the terms of this chapter as enacted or amended, such use may be continued, so long as it remains otherwise lawful, subject to the following provisions:

Where a lawful structure exists at the effective date of adoption or amendment of this chapter that could not be built under the terms of this chapter by reason of restrictions on area, lot coverage, height, yards or other characteristics of the structure or location on the lot, such structure may be continued so long as it remains otherwise lawful, subject to the following provisions:

Irrespective of other requirements of this article, if no structural alterations are made, any nonconforming use of a structure and premises may be changed to another nonconforming use of similar or less nonconformance, provided that the Board of Appeals, either by general rule or by making findings in the specific case, shall find that the proposed use is equally appropriate or more appropriate to the district than the existing nonconforming use. In permitting such change, the Board of Appeals may require appropriate conditions and safeguards in accord with the purpose and intent of this article. Where a nonconforming use, structure, or use and structure in combination is hereafter changed to a less nonconforming character, it shall not thereafter be changed to a greater nonconforming character.

On any building devoted in whole or in part to any nonconforming use, work may be done in any period of 12 consecutive months on ordinary repairs, or on repair or replacement of nonbearing walls, fixtures, wiring or plumbing to an extent not exceeding 25% of the building's replacement cost prior to the initiation of repairs, exclusive of foundations, provided that the cubic content of the building as it existed at the time of adoption or amendment of this chapter shall not be increased. Nothing in this article shall be deemed to prevent the strengthening or restoring to a safe condition of any building or part thereof declared to be unsafe by any official charged with protecting the public safety, upon order of such official.

A change of tenancy or ownership of a nonconforming use is allowed, provided there is no increase in the degree of nonconformance of the nonconforming use.

Whenever the boundaries of a district shall be changed so as to transfer an area from one district to another district of another classification, the provisions of this article shall also apply to any existing uses that become nonconforming as a result of the boundary changes.

Nonconforming buildings or structures may be structurally changed, altered or enlarged with the approval of the Zoning Board of Appeals when the Zoning Board of Appeals finds that the request is a case of exceptional hardship in which failure to grant the relief requested would unreasonably restrict continued use of the property or would restrict valuable benefits that the public currently derives from the property as used in its nonconforming status, except that any approval for structural changes, alteration or enlargement may be granted only with a finding by the Zoning Board of Appeals that approval will not have an adverse effect on surrounding property and that it will be the minimum necessary to relieve the hardship.

Nonconforming uses of structures or land existing at the effective date of this chapter that were established without a zoning compliance approval or without a valid building permit, or those nonconforming uses which cannot be proved conclusively as existing prior to the effective date of this chapter, shall be declared illegal nonconforming uses and are not entitled to the status and rights accorded legally established nonconforming uses by this article.

Permits for construction on, expansion of, or substitution of nonconforming lots, uses or structures require a zoning permit pursuant to Article XXIV. Other permits and approvals may also be required.

Residential dwelling units, which are existing and so used at the effective date of this chapter shall not be considered nonconforming structures for purpose of replacement as provided in §§ 155-19.07 and 19.09.