Legally preexisting buildings, lots and uses. This chapter shall not apply to legally preexisting buildings, lots and structures, nor to the legally preexisting use of any building, structure or land, but only to the extent to which it was used at the time of the original enactment of this chapter. This chapter shall apply to any new construction and/or any change in use, alterations, extension or movement of a building or structure and to any change in use of a building or structure and to any change in use of land subsequent to enactment of this chapter.