An ADU is any small dwelling unit —with its own bathroom and kitchen — that is built upon the same site as a primary residential building. These units are usually rented out to tenants. You may have also heard them referred to as mother-in-law apartments, in-law suites, guest houses, or granny flats. These spaces include units in attics, basements, rear additions, and backyard buildings (coach houses). These units are intended to host a single household.
ADUs can be constructed on properties that have existing, legal residential units. The Chicago ordinance makes a distinction between coach houses
, which are new units created in detached buildings in the backyard, and conversion units
, which are new units constructed in an existing principal residential building that is at least 20 years old, typically in attic or basement spaces.
Please refer to our manual for Building Better Basements