Accessory Structures in St. Clair County, IL (2026)

2 rules for unincorporated St. Clair County, Illinois.

Verified from official government sources

Note: These county rules apply to unincorporated areas of St. Clair County. If you live within an incorporated city, that city's own rules apply: see the city list below.

ADU Rules

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.

ADUs in Unincorporated St. Clair County

Some Restrictions

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.

Full ordinance details →Official source ↗

Shed & Carport Rules

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.

Shed Rules in Unincorporated St. Clair County

Some Restrictions

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.

Full ordinance details →Official source ↗

All St. Clair County ordinances

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