Subsequent to the effective date of these regulations, no change in the use or occupancy of land or any change in use of occupancy in an existing building, other than for single-family dwelling purposes, shall be made, nor shall any new building be occupied for any purpose other than a single-family dwelling until an occupancy compliance certificate has been issued by the Administrative Officer. Every occupancy compliance certificate shall state that the new occupancy complies with all provisions of these regulations and no subsequent modifications shall be made to the occupancy, use or method of operation that would be in violation of these regulations. All construction and occupancy compliance certificates shall be covered by a weatherproof material and shall be affixed to a sturdy sign, and displayed between the curb line and sidewalk at all times during construction. Failure to do so shall be a violation of this code.