The lawful use of a building, structure or property which existed at the time this chapter, or an applicable amendment to this chapter, took effect and which is not in conformity with the provisions of this chapter, including the routine maintenance of such a building or structure, may be continued, subject to the following conditions:
A.
No modification or additions to a nonconforming use or structure shall be permitted unless they comply with this chapter. The words "modification" and "addition" include, but are not limited to, any alteration, addition, modification, structural repair, rebuilding or replacement of any such existing use, structure or accessory structure or use. Ordinary maintenance repairs are not considered an extension, modification or addition; these include painting, decorating, paneling and the replacement of doors, windows and other nonstructural components and the maintenance, repair or replacement of existing private sewage or water supply systems or connections to public utilities. Ordinary maintenance repairs do not include any costs associated with the repair of a damaged structure. The construction of a deck that does not exceed 200 square feet and that is adjacent to the exterior wall of a principal structure is not an extension, modification or addition. The roof of the structure may extend over a portion of the deck in order to provide safe ingress and egress to the principal structure.
B.
If a nonconforming use or the use of a nonconforming structure is discontinued for 12 consecutive months, any future use of the building, structure or property shall conform to the appropriate provisions of this chapter.
C.
Any legal nonconforming use of property which does not involve the use of a structure and which existed at the time of the adoption or subsequent amendment of this chapter adopted under § 62.23(7)(h), Wis. Stats., may be continued although such use does not conform with the provisions of the chapter. However, such nonconforming use may not be extended or increased.
D.
The maintenance and repair of nonconforming boathouses which are located below the ordinary high-water mark of any navigable waters shall comply with the requirements of § 30.121, Wis. Stats.
E.
Uses which are nuisances under common law shall not be permitted to continue as nonconforming uses.