Continuance, expansion, reconstruction. It is the intent of this chapter to promote land use conformities. Any use of land, or any building, structure, or parts thereof, legally existing at the time of the adoption of this chapter, or at the time a zone or regulation is changed by amendment hereafter, which does not conform to the use requirements of this chapter, or its amendments, may continue but may not be expanded, reconstructed, structurally altered, or permitted to become more nonconforming in any way, except as specified below.