Proposal would allow over 22,000 homes in Ann Arbor to add accessory apartments Updated 12:39 PM; Facebook Share ANN ARBOR, MI — Ann Arbor officials say the city’s restrictions on adding accessory apartments to homes are keeping homeowners from building them, but new rules could allow them on over 22,000 properties. About a couple dozen Ann Arbor homeowners have applied to add accessory dwelling units — known as ADUs — to their properties since the city adopted an ADU ordinance in 2016. In some cases, ADUs can be in detached structures such as a carriage house or an apartment above a garage, or a separate rental unit within a home or home addition.