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 AD Ordinance Updates

Since the accessory dwellings ordinance was enacted in 2009, there have been only 20 AD permits approved. Under the Affordable Housing Master Plan updates to the current AD regulations were shown to be a tool that could help increase the supply of affordable housing. Accessory dwellings are a vital part of the Missing Middle Housing that would provide much needed access to additional housing options in our community, especially for small households and older adults as a way to age in place.

To kick off the update of the regulations, the County launched a Working Group made up of members of the Housing Commission, the Commission on Aging, the Civic Federation, and the Alliance for Housing Solutions to assist the county in encouraging greater use of ADs. In May, the County held a community forum on the upcoming accessory dwellings update.  Read more about the preliminary ideas discussed at the May forum here.

AHS will be examining the issue of accessory dwellings at its September 20th2017 Leckey Forum. Check back here for more information on the tools and options under consideration as the County’s process moves forward.

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County Resources