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

Section 36-971(a)(6) lists the non-paying guest house as one of the accessory uses allowed alongside a principal home in unincorporated Kendall County, but its conditions are tight. The structure cannot include kitchen facilities, which keeps it from functioning as an independent dwelling unit, and its use is restricted to the occasional housing of guests of the occupants of the principal building, explicitly barring permanent occupancy by others, language that rules out long-term tenants, rental income, or a caretaker living there full time. The Code confines the use to larger lots and specific zoning: only permitted on parcels of three acres or more in the A-1 Agricultural District or R-1 district, so a standard suburban-sized unincorporated lot, or one zoned R-2 through R-7, cannot add this kind of accessory living space no matter its acreage.

Because the guest house is an accessory building, it must also satisfy Section 36-971's general accessory-structure rules: it cannot be built before the principal residence begins construction outside the A-1 district, it must sit at least five feet from side and rear lot lines and ten feet from the main house unless attached, and it is capped by the accessory-building height table at 25 feet in R-1 or no limit in A-1. Kendall County has no separate accessory dwelling unit ordinance permitting a rentable second unit with its own kitchen; a property owner wanting that must pursue the special use secondary dwelling unit path available only inside an RPD-1 planned development under Section 36-365(a)(15), which carries its own historic-preservation and deed-restriction conditions.