Pursuant to Section 62.23(7)(h), Wis. Stats., a nonconforming use may not be extended. The total structural repairs and alterations in such a nonconforming use's building, premises, structure, or fixtures shall not during its life exceed fifty percent (50%) of the assessed value of the building, premises, structure, or fixture unless permanently changed to a conforming use. The nonconforming use of a structure, land, or water existing on the date that the nonconformity came into being may be continued although the use does not conform with the provisions of this Chapter, except that:
(a) Change to More Restrictive Use Category. The nonconforming use of a structure may be changed to a use of the same or more restricted classification, but where the nonconforming use of a structure is hereafter changed to a use of a more restrictive classification, it shall not thereafter be changed to a use of a less restricted classification.
(b) Discontinuation of Nonconforming Use. If a nonconforming use is discontinued or terminated for a period of twelve (12) months, any future use of the structure, land or water shall conform to the provisions of this Chapter.
(c) Maintenance of Nonconforming Use Parcels. Parcels containing a nonconforming use of land or water may be maintained or repaired including grading, paving, and surfacing, or the repair and replacement of bumper or wheel stops, fences, screening and drainage ways, provided that the amount of land, water or storage (i.e. vehicles, equipment and/or materials) devoted to such nonconforming use as it existed prior to the date that the nonconformity came into being is not extended, enlarged or moved.