Accessory Dwellings


Accessory dwellings are additional, often small, housing units located within or adjacent to single-family homes. They are frequently known by more descriptive names such as basement apartments, granny flats, backyard cottages, in-law suites, and carriage houses. A property owner with an accessory dwelling can live in either the main dwelling or the accessory dwelling while renting out the other unit.

Arlington County adopted an ordinance in 2008 that allows accessory dwellings generally no greater than 750 square feet within a single-family home. Detached accessory dwellings – such as backyard cottages or detached carriage houses – are not currently allowed in Arlington.

Accessory dwellings are one way of adding to the supply of housing in single-family neighborhoods without altering the character of the area. Because of their size and characteristics, these units are often rented at rates that can be affordable to low- or moderate-income individuals.

2017 ADU Ordinance Updates

In 2017 Arlington County is working on an update of the 2008 ADU ordinance to encourage more of these units in Arlington. See the latest information on the update process here.

 Learn More

  • The website provides numerous examples of real accessory dwellings with photos, floor plans, and owner stories.
  • Arlington’s accessory dwelling permit process is managed by the zoning office of the Department of Community Planning, Housing, and Development.