Conformance with zoning regulations. Zoning affects every structure and use. Except as hereinafter specified, no building, structure or premises shall hereafter be used or occupied, and no building or part thereof or other structure shall be erected, moved, placed, reconstructed, extended, enlarged, or altered, except when in conformity with the regulations herein specified for the zoning district in which it is located. In case any building or part thereof is used, erected, altered or occupied contrary to law or to the provisions of this chapter, such building shall be declared a nuisance and may be required to be vacated, torn down, or abated by any legal means and shall not be used or occupied until it has been brought into conformance. If construction on a building is lawfully begun prior to adoption of this chapter, nothing in this chapter shall be deemed to require any change in the planned or designed use of any such building, provided that actual construction is being diligently carried on, and further provided that such building shall be entirely completed for its planned or designed use within one year from the effective date of the ordinance from which this chapter is derived, or affecting amendment.