No building permit by the Code Enforcement Official, lawfully issued prior to the effective date of this Zoning chapter, or of any amendments hereto, and which permit, by its own terms and provisions, is in full force and effect at said date, shall be invalidated by the passage of this Zoning chapter, or any such amendment, but shall remain a valid and subsisting permit, subject only to its own terms and provisions and laws, rules and regulations pertaining thereto, and in effect at the time of the issuance of such permit, provided that all such permits shall expire not later than 60 days from the effective date of this Zoning chapter, unless actual construction shall have therefore begun and continued pursuant to the terms of said permit.