5 rules for unincorporated St. Clair County, Illinois.
Verified from official government sources
St. Clair County's Zoning Ordinance does not authorize a standalone accessory dwelling unit. Residential districts allow only one detached one-family dwelling; caretaker accommodations are permitted but not as a separate detached second home. Incorporated cities set their own ADU rules.
St. Clair County Zoning Ordinance Sec. 40-4-13
Accommodations for professional servants, caretakers, watchmen, or custodians, but not as a separate detached one-family dwelling.
A one-story storage shed of 120 sq ft or less needs no building permit; 120 to 200 sq ft needs a $25 permit and over 200 sq ft a $120 permit. Detached accessory buildings must sit at least 5 feet from side and rear lot lines.
St. Clair County Building Code Sec. 7-1-28(A)(1)
One-story detached accessory structures used as tool and storage sheds, playhouses and similar uses, provided the floor area does not exceed 120 square feet.
The county has no ordinance section specifically on converting a garage to living space. Any conversion that adds a dwelling unit or alters the structure needs a building permit and must meet Building Code and Zoning Ordinance dwelling and setback standards. Cities set their own rules.
Private carports are a permitted accessory use in single-residence districts. As a detached accessory structure a carport must be at least 5 feet from side and rear lot lines, 10 feet from the house, and no more than 25 feet tall, per the county Zoning Ordinance.
St. Clair County Zoning Ordinance Sec. 40-4-13
Private tool sheds, garages or carports, tennis courts, patios.
St. Clair County has no tiny-home ordinance. A permanent tiny house is a dwelling that must meet minimum-lot standards, the adopted building code and dwelling requirements. Temporary structures used as living quarters are barred except during construction. Cities set their own rules.
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