When the owner of a lot of record located at the intersection of two (2) streets requests to construct a main building, or construct an addition to an existing main building on a lot of record, the building line for such main building or addition shall be established on the side street from the side property line by calculating twenty-five percent (25%) of the front lot line width; but in no case shall this building line be less than twelve (12) feet from the side property line. The front building line for an interior lot of record shall be established as the average of the front building lines of the two (2) main buildings on either side of the lot of record under consideration; however, if building lines are delineated on the side street of a subdivision plat of record, such lines shall be the prevailing and required building lines.