A lawful preexisting nonconforming use may be expanded (or subject to a series of expansions) by special exception approval, so long as the total percentage increase of the nonconforming condition that existed at the time of enactment of the ordinance that created the nonconforming condition is not increased by an aggregate amount greater than 100% of the nonconformity. The extent of the nonconforming use expansion shall be regulated based upon both total building floor area and total impervious coverage for the nonconforming use. This provision shall not allow an increase in a nonconforming height or an increase of the nonconformity of a sign or the number of nonconforming dwelling units.