Any nonconforming structure or use lawfully existing on the effective date of this title, or any subsequent amendments to this title, may be continued and maintained in conformance with provisions of this chapter, provided no enlargement of area, space or volume occupied by the nonconforming use occurs. Any nonconforming structure authorized by a valid building permit prior to the effective date of the ordinance codified in this title, or any subsequent amendments to this title, may be completed and used in accordance with the plans, specifications and regulations under which such permit was issued. Expiration of authorized permits will result in a loss of vested right for construction and use of such structure. (Ord. 4229 § 2, 1987.)