Whenever a zoning lot existing on December 15, 1961, or on any applicable subsequent amendment thereto, is divided by a boundary between districts in which different uses are permitted, the use regulations applicable to the district in which more than 50 percent of the lot area of the zoning lot is located may apply to the entire zoning lot, provided that the greatest distance from the mapped district boundary to any lot line of such zoning lot in the district in which less than 50 percent of its area is located does not exceed 25 feet. Such distance shall be measured perpendicular to the mapped district boundary.

Whenever the use regulations are so applied, the district boundary may be assumed to be relocated accordingly, and the bulk, off-street parking and loading, and all other regulations applying to such expanded district shall apply to the entire zoning lot. However, when the zoning lot is divided by a district boundary between a district limited to single- or two-family residences and a district permitting multiple dwellings, the use and bulk regulations of an R3-2 District shall apply in the R1, R2, R3A, R3X or R3-1 portion, and the use and bulk regulations of an R4 District shall apply in the R2X, R4A, R4-1 or R4B portion.

Except as specifically provided by the provisions of a special purpose district, the provisions of this Section shall apply to zoning lots which are divided by a special purpose district boundary line.