County Seeks Input on Detached Accessory Dwellings

Pictured above: an example of an accessory dwelling currently not allowed in Arlington. Image courtesy of Radcliffe Dacanay |  Flickr

Pictured above: an example of an accessory dwelling currently not allowed in Arlington. Image courtesy of Radcliffe Dacanay | Flickr

Arlington County staff have released a set of new recommendations that would allow homeowners to build new detached accessory dwellings, a.k.a. backyard cottage, on their properties and to renovate existing detached buildings to create new accessory dwellings (see summary below).

You may recall that detached accessory dwellings were the one item left out of the 2017 update to the County’s accessory dwelling standards. At the time, staff had proposed allowing a one foot setback but were asked by the County Board to do additional research. These new recommendations are proposing a five foot setback for new or expanded buildings.

Accessory dwellings are helpful tools for providing additional housing options throughout our community.

They also provide an addition source of income for homeowners. Although they are not required to be rented at affordable rates, they are more likely than other new apartments to be affordable given their modest size and features. (Learn more about accessory dwellings here.)

Summary of Arlington County Staff Recommendations

Requirements for New Detached Structures:

Currently no new construction of detached AD structures is allowed. The new proposal would allow them if…

  • Up to 1.5 stories or 25 feet tall

  • Set back from side or rear property line by minimum of five feet

  • Max footprint of 560 square feet in an R-5/R-6 district or 650 square feet in other R-districts

  • Max size of 35% of combined floor area of main and AD unit, up to a max of 750 square feet

  • Occupied by no more than 3 people

Requirements for Vertical Expansion of Existing Accessory Building (e.g. detached garage)

Currently only interior alterations are allowed for existing “grandfathered” detached accessory buildings being converted into ADs. The new proposal would allow an existing structure not meeting the New Detached Structures rules (e.g. those closer than 5 feet from the property line) to be expanded if…

  • No expansion of building footprint

  • Expansion limited to max of 25 feet or 1.5 stories

  • New walls of expansion are not closer than five feet from any side or rear lot line (the same distance in the New Detached Structures proposal)

  • Same maximum sizes and occupancy as new structures

Expected Timeline to Adoption

March 12, 2019: Zoning Committee of the Planning Commission (ZOCO) meeting
March 15, 2019: Online written input closes
March 28, 2019: Urban Forestry Commission meeting
April 15, 2019: Commission on Aging meeting
April 23, 2019: County Board Request to Advertise
May 6, 2019: Planning Commission final consideration and recommendation
May 9, 2019: Citizens Advisory Commission on Housing (Housing Commission) meeting
May 18, 2019: County Board final consideration and action