What are 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. 

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. 

Arlington County adopted an ordinance in 2008 that allowed 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 – were not allowed in Arlington. In December 2017, the County Board approved updates to the ordinance that streamlined the rules and allows conversion of existing detached accessory buildings (such as garages) to be converted to accessory dwellings. 


Learn More

Arlington’s accessory dwelling permit process is managed by the zoning office of the Department of Community Planning, Housing, and Development.  Follow the links below to learn more.

The website www.accessorydwellings.org provides numerous examples of real accessory dwellings with photos, floor plans, and owner stories.