Will County, IL Accessory Structures: ADU Owner Occupancy (2026)

Owner occupancy. The owner of record must reside in either the principal or accessory dwelling unit for a minimum of six months of each calendar year.

(e)   Methods of creation. An accessory dwelling unit may be created through any of the following methods:

1.   Converting existing area within the interior of a house (e.g., attic or basement) to an ADU;

2.   Adding floor area to an existing house to accommodate an ADU;

3.    Constructing a detached accessory dwelling unit on a parcel with an existing house;

4.   Converting space within a detached accessory building; or

5.    Constructing a new house with an internal or detached accessory dwelling unit.

(f)   Number of residents. The total number of residents that reside in the accessory dwelling unit and the principal dwelling unit, combined, may not exceed the number permitted for a household.

(g)   Location of entrances. Only one entrance to a house containing an accessory dwelling unit may be located on a facade that faces a street, unless the house contained an additional street-facing entrance before the accessory dwelling unit was created. Detached ADUs are exempt from this regulation.

(h)   Size. The floor area of an ADU may not exceed 49% of the gross floor area of the principal dwelling unit on the subject lot (excluding any attached garage), or 650 square feet, whichever is less.