To avoid undue hardship, nothing in this title shall be deemed to require a change in the plans, construction, or designated use of any building on which actual construction was lawfully begun prior to the date of adoption of the ordinance codified in this title, and upon which actual building construction has been carried on diligently. “Actual construction” is defined to include the placing of construction materials in permanent position and fastened in a permanent manner. Where excavation or demolition or removal of an existing building has been substantially begun preparatory to rebuilding, such excavation or demolition shall be deemed to be actual construction, provided that work shall be carried on diligently. (Ord. 691 §48, 1984).