To avoid undue hardship, nothing in this chapter shall be deemed to require a change in the plans, construction, or designated use of any building, structure or use for which a building permit has been legally issued prior to the effective date of adoption or amendment of the ordinance codified in this title, except that applications for extension of a building permit shall not be approved to exceed a period of one year from the date of adoption or amendment. (Ord. 4128 (part), 1981; Ord. 3380 (part), 1968).