A use, building or structure, lawfully in existence
at the effective day of this chapter, which shall be made nonconforming
at the passage of this chapter may be continued except as otherwise
provided in this section.
Where a lot exists as a separate isolated lot
and is improved with a building or structure which is nonconforming
due to location, said lot may be further improved by an addition to
said building or structure or any accessory building or structure
(provided that the existing nonconforming setbacks may be extended
but not further encroached upon).
Notwithstanding any other provisions of this
section, any existing lot not adjoining any other land owned by the
owner of such lot and which is nonconforming as to dimensions or area
may be improved with a new building or structure, in accordance with
the use requirements of this section, provided that the minimum setbacks
shall be as required in the zoning district; except that required
side street setbacks on corner lots may be reduced one foot for each
three feet the lot is under the minimum width required in the zone
district but shall not be reduced below 1/2 the minimum required setback.