Accessory Structures in Madison County, IL (2026)
2 rules for unincorporated Madison County, Illinois.
Verified from official government sources
ADU Rules
Unincorporated Madison County allows accessory dwelling units only as a special use in the Agricultural District, on lots of two acres or more, capped at 1,000 square feet, under Zoning Code § 93.023(D)(44). The countywide definition in § 93.007(B) sets that same size cap.
Madison County Accessory Dwelling Unit Rules
Significant RestrictionsMadison County Code §§ 93.007(B), 93.023(D)(44)
ACCESSORY DWELLING UNIT. A residential dwelling unit, not including mobile homes, within an accessory structure located on the same lot as a single-family dwelling. ACCESSORY DWELLING UNITS shall not take up more than 1,000 square feet of an accessory structure. ... (44) Accessory dwelling units on lots at least two acres in size, where the dwelling unit located within an accessory structure ...
Shed & Carport Rules
In unincorporated Madison County, sheds and other accessory buildings on residential lots are capped at 20 feet tall, must sit at least 5 feet from the side lot line and 7.5 feet from the rear, and cannot cover more than 30% of the rear yard.
Madison County Accessory Building & Shed Rules
Some RestrictionsMadison County Code § 93.051(A)
(A) All agricultural, conservation, and residential districts. ... (2) The maximum height of any accessory buildings shall be as follows: (a) Twenty-five feet for agricultural and conservation districts. (b) Twenty feet for residential districts. (3) An accessory structure shall be: (a) A minimum distance of five feet from any other building on the property. (b) In residential dis...
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