No lot, piece or parcel of land in single ownership on the effective date hereof, whether improved or vacant, shall be assembled, divided or subdivided unless each resulting part thereof shall conform to the minimum lot area requirements of this chapter applicable thereto and unless buildings on each part thereof shall conform to the setback, yard, lot area, occupancy and other provisions of this chapter applicable thereto after such division or subdivision. In determining conformity, contiguous land of the grantee of any such part shall be considered.