Each detached garage, accessory building and structure shall be located at least five feet farther back from the front property line than is the front wall of the dwelling; provided, however, that with respect to any corner lot, any detached garage, accessory building or structure shall be located only in the innermost corner of the lot (that is, the corner farthest removed from the abutting streets), at least 15 feet from the two nearest property lines, and so that the two nearest property lines do not abut any street.