Dedication requirements for streets and sidewalk improvements shall be subject to the following conditions:

    A.    The maximum area of land required to be so dedicated shall not exceed twenty-five percent of the area of any such lot as such lot existed on the effective date.  In no event shall such dedication reduce the lot below the minimum lot size required within its zone;

    B.    No such dedication shall be required with respect to those portions of such a lot presently occupied by a building which was existing on the effective date and which will continue to exist following the completion of the work proposed in the building permit;

    C.    No additional improvement shall be required on such a lot where complete roadway, curb, gutter and sidewalk improvements exist within the present dedication contiguous thereto; provided, however, required additional dedications for future street construction shall be made;

    D.    No building or structure shall be erected on any such lot after the effective date within the area of dedication required by this chapter. (Prior code § 21-13)