Accessory Dwelling Units

An ADU (accessory dwelling unit) is an additional, self-contained dwelling on a typical single-family lot. It can be attached, such as in the lower level of the main dwelling, or detached at the rear of the property.  These smaller units represent the “missing middle,” filling the gap between single-family homes and multi-unit dwellings downtown. While ADUs are not the sole answer to Decatur’s missing middle, they represent a big step in the right direction. Residents of ADUs contribute to the vitality of the community, and ADUs make it possible for more families to own and maintain a home in the city. 

ADUs were permitted as a housing type in December 2012. They are allowed in most single-family and multi-family residential zoning districts – R-85, R-60, R-50, RM-18, RM-22, and RM-43. One ADU per primary dwelling unit is possible. Other considerations: 

  • An ADU may be developed in or to the rear of an existing or new main dwelling. 
  • To keep true to its accessory size, an ADU may have a floor area up to 800 square feet, and should not exceed 40 percent of the floor area of the primary dwelling. If the ADU is combined with the garage, the total floor area may be up to 1,000 square feet.
  • An ADU may have up to two bedrooms. 
  • The owner is required to reside in either the main dwelling or the ADU for at least eight months of the year; an affidavit will be required of the owner confirming residency. 
  • If detached from the main dwelling, an ADU must be located in the rear yard and have a footprint no greater than 30 percent of the rear yard.  
  • In combination with the main dwelling, the total floor area should not exceed 40 percent of the lot area. 
  • Similarly, the total lot coverage of all impervious surfaces should not exceed 40 percent of the lot area. 

As a housing option, ADUs demonstrate the values of diversity and affordability promoted by the City of Decatur. They serve to fill a gap in Decatur’s housing market by providing a new, neighborhood scale rental housing option for those looking for affordable living arrangements in a more traditional single-family-home setting.