What are Accessory Dwelling Units (ADUs)
An Accessory Dwelling Unit is a second, smaller dwelling unit 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). ADU Guidebook
Adopted ADU Changes as of 2021
The changes include allowing ADUs in more zoning districts and relaxing the standards in zoning districts where ADUs are currently allowed. These changes eliminate the requirement that the ADU must be in an existing detached building; newly constructed detached ADUs will be allowed. The proposed changes would also allow ADUs in the R3 Townhouse and R4A, R4B, R4C, R4D and R4E Multiple-Family Dwelling Districts when the lot has one single-family home on it.
Interactive Map Tool
An interactive map to explore the potential areas where ADUs would be permitted throughout the City: ADU Map
ADU requirements may be found here.
Please reference 5.16.6 D - Accessory Uses and Structures.
February 9, 2021 Planning Commission Working Session
Questions and comments may be submitted in advance to City of Ann Arbor Planning Services by emailing to [email protected].
Frequently Asked Questions
How does the creation of an ADU impact property tax assessment?
The PRE (Primary Residence Exemption) is based on the percentage occupied by the owner, the unit would be assessed similar as a 2 family rental. The assessment would also increase for extra finish and kitchens.
What are the neighborhood notification requirements for a new ADU?
No neighborhood notifications requirements exist. Although no site plan, public hearing, or public notice are required, building permits are necessary for construction.
How many ADUs have been proposed since the 2016 amendments were approved?
Since 2016, 43 applications for ADUs have been submitted. Some are currently under review, some are under construction, and some have been completed.
The code for ADUs mentions a “family". What is the City's definition of a “family"?
Limits on Occupancy of Dwelling Unit:
- Dwelling Unit may be occupied by one of the following Family living arrangements:
- One or more Persons related by blood, marriage, adoption, or guardianship living as a single Housekeeping Unit, in all districts.
- A maximum of four Persons plus their Offspring living as a single Housekeeping Unit, in all districts.
- A maximum of six Persons living as a single Housekeeping Unit in Multiple-Family and mixed use districts only.
- A Functional Family living as a single Housekeeping Unit that has received a Special Exception Use permit pursuant to Section 5.29.5
How do ADUs advance City planning Goals?
ADUs advance a number of stated City planning goals including: a) increasing housing diversity, b) increasing housing affordability (by increasing the supply of new rental housing), c) supporting transit (by increasing density in existing neighborhoods near transit corridors), d) encouraging individuals to age in place or age with family nearby, e) reducing the amount of impervious surface per dwelling unit (since ADU's will be built in neighborhoods that already have streets, driveways and sidewalks), f) allowing property owners a diversity of possible uses by allowing an ADU to be used by an aging relative, used as a home office, used by children of the owner who are returning to town, and/or used as a rental unit for added income.
