A second residential unit within and subordinate to an existing single family home. Designed to be complete; usually has separate access. Usually managed through a special permit process. Approval can be based on a wide variety of criteria: eligibility of applicants or occupants, size, location or design of unit, duration of permit or saturation within a given area, or parking, water/ sewage, or additional health and safety provisions. Conditions designed to lessen impacts (traffic, parking, aesthetics) generally upheld.


To provide a source of revenue for homeowners while providing additional housing opportunities for members of the community, especially those with limited incomes.


Political challenge to create support for neighborhood intensification.

Capacity Requirements:

  • Technical studies required to support the plan.
  • On-going oversight may be required to insure enforcement.


Can create a diversity of housing stock to meet a wide variety of community needs over time and contribute to making complete neighborhoods.


Westchester County model ordinance resource link

AARP All About ADUs resource link.