Accessory Dwelling Units

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What are Accessory Dwelling Units (ADUs)ADU pic 4.png

An Accessory Dwelling Unit is a second, smaller dwelling units either developed out of an existing single family house (such as a basement, attic or addition) or as part of an accessory structure (such as a converted garage or carriage house). 

Currently, the City of Ann Arbor Zoning Ordinance allows for these units to be developed in the primary residence through a special exemption process, with additional requirements that the occupant be related and not pay any rent.

Ann Arbor ADU Guidebook (PDF)

ADU Archive

Amendments Approved on August 4, 2016 City Council approved amendments on August 4, 2016 to the Zoning Ordinance to allow ADUs in single-family residential zoning districts meeting certain requirements. Below is more information regarding City Council and Planning Commission action history, general information about accessory dwelling units, and resources associated with this planning initiative. 

City Council Action

Second Reading, Public Hearing and Action Vote - City Council approved amendments to the Zoning Ordinance regarding ADUs following a second reading and a public hearing at the August 4, 2016 meeting. 

First Reading - City Council passed the first reading of the amended proposed ordinance at their July 7, 2016 meeting.  A second reading and vote on the amended proposed ordinance will be held in one month, on Thursday, August 4, 2016.  The Staff Memo (PDF) for the first reading is available. 

Planning Commission Recommendation

On Tuesday, April 19, following a public hearing, the Planning Commission recommended approval of the proposed ordinance (PDF) to the Zoning Ordinance regarding accessory dwelling units.  The Planning Commission also asked staff to develop a draft guidebook for homeowners with information on how to develop an ADU and suggest options on how to preserve affordability of the ADUs, potentially with the use of other incentives already available to the City.  The draft guidebook will accompany the proposed amendments for City Council consideration.   

Why are we talking about changes?

Ann Arbor's made accommodations in their ordinance to accommodate ADUs in 2001-2002.  However, only 2 units have been applied for and approved.  Since that time, the housing market went through a boom, bust and recovery.  The 2015 Housing Affordability and Economic Equity Analysis documented increasing housing costs in Ann Arbor in particular, which were pricing out moderate income and working families as well as young adults and seniors.  One of the recommendations in the study was to consider Accessory Dwelling Units with the lens of adding additional affordable housing units, while also providing some income to existing home-owners which could help existing residents stay in their homes.

Ann Arbor City Council requested that the Planning Commission consider changes to more easily allow for ADUs in Ann Arbor, effectively starting this process.


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​Planning & Development Services
301 E. Huron St.
Ann Arbor
Planning Manager

Brett Lenart, AICP 
734.794.6000 x42606