Accessory dwelling units

Who does this land on?

Owners of one and two family houses in the outer boroughs, buyers pricing a lot on the assumption a second unit can be added, and anyone converting a garage or a rear structure.

What governs it?

• The Zoning Resolution as amended, which sets where an accessory dwelling unit is permitted and on what conditions
• The construction codes, which set egress, light, air, ceiling height and fire separation for the new unit
• The Multiple Dwelling Law and the Housing Maintenance Code, which apply once the building crosses into multiple dwelling territory
• Flood hazard area requirements, which restrict habitable space below the design flood elevation
• The Landmarks Preservation Commission, where the property is landmarked or in a historic district

How does the process run?

1. Confirm the zoning district and whether the amendment reaches it, because the permission is not citywide
2. Confirm the lot conditions the amendment requires, including lot type and whether the property sits in a mapped flood hazard area
3. Confirm the property is not in a historic district or subject to a restriction that would foreclose the work
4. Test the proposed space against the construction code requirements for a dwelling unit, which is where garages and cellars usually fail
5. File an alteration application through a registered design professional and obtain an amended certificate of occupancy
6. Complete the work, pass inspections, and get the amended certificate before the unit is occupied or advertised

Where does it bite in a transaction?

• A lot is bought at a premium for an accessory unit the district does not permit
• A garage conversion is designed before anyone checks the flood map
• A unit is completed and occupied before the amended certificate issues
• A rental listing goes up for a unit the City has never approved, which is how the complaint arrives

What else should you read before you file or sign?