Joliet, IL Accessory Structures: ADU Impact Fees (2026)

Illinois municipalities operate under a limited impact-fee framework. The Illinois Road Improvement Impact Fee Law (605 ILCS 5/5-901 through 5-919) authorizes counties of more than 400,000 population to adopt road impact fees following a comprehensive road improvement plan and an advisory committee process; Will County (population approximately 700,000) qualifies and has used this authority in select unincorporated areas, but the fees apply to county roads and not generally to in-city Joliet permits. School impact fees are not authorized by statewide statute; school districts are funded through the state evidence-based funding formula and local property tax levies under the Property Tax Extension Limitation Law (35 ILCS 200/18-185 et seq.). Joliet, as a home-rule municipality, may impose connection fees and capacity charges on utility services through its home-rule authority under Article VII Section 6 of the Illinois Constitution, subject to rational-nexus principles. Typical costs to add a second dwelling on a Joliet parcel include: (1) zoning review fees through Planning; (2) building permit fees calculated on construction valuation under the Illinois Residential Code; (3) plan review fees as a percentage of the building permit; (4) Joliet Public Utilities water and sewer tap charges if a new service is installed (sharing the existing tap with the principal dwelling avoids most connection charges); (5) Joliet Will County recording fees for any easements or covenants; (6) potential Will County stormwater management or road impact fees on greenfield work. Property taxes on the increased Will County assessed valuation provide the long-term revenue stream to Joliet Public Schools District 86, Joliet Township High School District 204, Joliet Junior College District 525, and other taxing bodies.