For non-residential uses, other than non-profit hospital staff dwellings, the Board of Standards and Appeals may extend the maximum permitted radius for off-site parking spaces located in Commercial or Manufacturing Districts, as specified in Sections 25-53 (Off-site Spaces for Permitted Non-residential Uses), 36-43 (Off-site Spaces for Commercial or Community Facility Uses) or 44-32 (Off-site Spaces for All Permitted Uses), from 600 to 1,200 feet, whenever the Board finds:

(a)        that the required accessory off-street parking spaces cannot reasonably be provided on the zoning lot because of physical conditions including irregularity, narrowness or shallowness of lot size or shape, or exceptional topographical or other physical conditions; and

(b)        that, within 600 feet of a boundary of the zoning lot, there is substantial difficulty in obtaining a site of sufficient size to accommodate the required accessory off-street parking spaces because such sites are occupied by substantial improvements.