Accessory Apartments and Dwelling Units

Learn more about creating an accessory dwelling in your basement, above or in a garage or by building a new freestanding structure.

An Accessory Dwelling, also known as an Accessory Dwelling Unit (ADU), is a secondary structure or apartment on a single family lot. It has it’s own kitchen, bathroom and a separate entrance. The unit can be attached to the main house or detached.

Accessory Apartment. Converting a basement in a rowhouse or a single family house into an apartment.

Accessory Apartment Addition. Building an addition on a house to create a separate apartment

Detached Accessory Dwelling Unit. Building a new free-standing structure or adding a living unit over a new or existing garage.

These versatile units can be a great fit for multi-generational, non-traditional and blended families and used as:

  • Living space for an elderly parent
  • Living space for adult children
  • Living quarters for a nanny or caregiver
  • Guest quarters
  • Long-term rental apartment
  • Short-term rental of bedroom or apartment (Airbnb)
  • Owners can move into this space and rent out the main house

As the units increase the supply of reasonably-priced housing, local jurisdictions have recently changed or are reviewing residential zoning laws to allow for an ADU as a “matter of right,” so it can be built with a permit and does not require a zoning variance. Creating this type of unit, especially a new structure on your property, is a substantial investment. However, it is worth considering due to the income that can be generated, as well as tax benefits.

Under the right conditions, they can provide additional income that can allow a homebuyer to borrow additional money.

Design Considerations

If it is attached, placement of separate entry/separation from main house

If detached, creating privacy from main house

Universal design/accessible features

Open floorplan

Above an existing garage

Parking spaces

Outdoor areas – how it ties to existing home’s yard and entertaining areas