Any additions to a nonconforming use (e.g., an existing duplex in a single-family zone) that would expand or intensify the nonconforming use. Expansions/additions to such nonconforming uses shall not be considered an intensification when the combined development of all units on the subject property does not exceed the cumulative limitations of the underlying zone. Where more than one dwelling unit exists on a legal lot, the development allowances of the underlying zone shall be applied on a pro-rata basis (for example, if two dwelling units exist on one lot, each would be allowed one half of the lot coverage and/or floor area ratio applicable to the zone). Where all of the units on the lot are under common ownership, or, in the case of multiple ownership, where all owners of units on the property are in agreement, a different combination of percentages may be established and recorded on the subject property by covenant.