Cook County, IL Accessory Structures: ADU Rules (2026)

Administration of the zoning ordinance shall be exercised through a person in the Department of Building and Zoning designated as the Zoning Administrator. All permits for use of land or buildings and certificates of occupancy, except as otherwise provided by the zoning ordinance, shall be reviewed and approved by the Department of Building and Zoning. The Zoning Administrator shall affix a certificate to the permit indicating that the proposed building or structure complies with all the provisions of this ordinance. [...] In order to provide a streamlined approval process for minor modifications of selected zoning standards, the Zoning Administrator is hereby given the authority to review and approve applications for variances of ten percent or less of the regulations as to location of structures or as to bulk requirements without referral to the Zoning Board of Appeals and without a public hearing in accordance with the zoning ordinance. [...] A "variance" means a grant of relief from the requirements of the Cook County Zoning Ordinance which permits construction in a manner that would otherwise be prohibited by the Ordinance. A "special use" of land or buildings, or both, described in the Cook County Zoning Ordinance is a use subject to special provisions because of unique characteristics that do not allow the use to be properly classified as a permitted use.