Occupancy Permits. No building or structure or part thereof shall hereafter be constructed or altered until issuance of a proper permit. No new use, extension or alteration of an existing use, or conversion from one use to another, shall be allowed in any building, structure or land or part thereof until issuance of a proper permit; except that no permit shall be required for the raising of agricultural crops, orchards or forestry. No occupancy permit shall be issued for any use or change in use unless such use or change in use is in conformity with the provisions of this Chapter. Notwithstanding any Building Code provision to the contrary, temporary occupancy permits are disfavored and may not be issued except upon specific application to and authorization by the Director of Public Works and, if otherwise authorized, may be approved at the discretion of the Director only in cases where the applicant in writing has demonstrated clear and substantial hardship necessitating issuance.