Joliet, IL Accessory Structures: ADU Permits (2026)

A Joliet homeowner pursuing a second dwelling unit on a single-family parcel works through several overlapping frameworks. First, the Zoning Ordinance (Chapter 47) establishes residential districts including R-1 (single-family), R-2 (two-family), R-3 (multi-family), and mixed-use districts. A second independent dwelling generally requires that the lot sit in R-2 or a higher-density district where two-family or multi-family use is permitted by right, or that the owner obtain a variance or special use permit from the Zoning Board of Appeals through the process in Chapter 47. Second, Section 47-5.3 of the Zoning Ordinance governs accessory uses incidental to a principal residential use; this section traditionally has not been read to authorize a second fully independent dwelling with its own kitchen, bathroom, and external entrance. Third, the Illinois Residential Code (Capital Development Board adoption of the International Residential Code under 71 Ill. Adm. Code 600) governs construction; building permits are issued by the Joliet Inspectional Services Division within the Department of Community and Economic Development. Fourth, the Illinois Plumbing Code (77 Ill. Adm. Code 890) governs water and sewer fixtures, requiring an Illinois-licensed plumber. Fifth, the Illinois Fire Code (adoption of NFPA 1 by the Office of the State Fire Marshal) and Joliet Fire Prevention Bureau review egress and separation. Homeowners should confirm the parcel's current zoning with the Joliet Planning Division at 815-724-4050 before designing.