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

UDO Sec. 2 permits an accessory dwelling in any residential district, but locks it to a detached principal dwelling: the lot's principal use must be a detached dwelling, no more than one accessory dwelling may sit on a lot, and it must be owned by the same person as the principal dwelling. 2-7, the accessory dwelling must be located within the primary dwelling itself rather than in a separate building. It must share the same driveway as the principal dwelling, and its floor area cannot exceed fifty percent of the principal dwelling's floor area, with a floor-area floor of 350 square feet and a ceiling of 800 square feet regardless of the main home's size.

If the accessory dwelling has its own separate entrance from the principal dwelling's entrance, that entrance cannot face any street the lot fronts on, preserving a single-family street appearance. Where the dwelling is placed in a detached accessory structure under the limited exception, that structure must also function as a garage for the residents of the principal dwelling, tying the ADU concession to garage space rather than a freestanding guest house. Finally, the code bars using the accessory dwelling as rental property for non-family members, restricting it to family occupancy such as an in-law suite rather than an income-generating rental unit.