St. Clair County, IL Building Setbacks & Zoning: Lot Coverage Limits (2026)

Column K of the Minimum Area, Bulk, Yard Requirements table in Sec. 40-3-7 sets the maximum building coverage as a percentage of lot area for every zoning district in unincorporated St. Clair County. The 'A' Agricultural District (Line 1) and the three-acre RR-3 district (Line 2) carry no listed percentage cap, marked '---' in the table, reflecting the low-density farm and large-lot character of those districts. Moving up in density, the RR-1, SR-1, SR-2 and SR-3 residential districts (Lines 3-6) are held to 20% lot coverage.

The SR-MH manufactured-housing district, the MHP mobile home park district, the MR-1 and MR-2 multi-family districts, and the NB neighborhood business and HB highway business districts (Lines 7-13) are held to 30%. The most intensive districts, B-2 general business, I-1 light industrial and I-2 heavy industrial (Lines 14-16), are capped at 40%. The same table also fixes each district's minimum lot size, yard setbacks and maximum building height, so a coverage calculation has to be read against those companion columns; a note to the table cross-references Sec.

40-4-3 for the primary farm residence exception. A property owner who cannot meet the percentage for their district can apply for an Area/Bulk Variance under Sec. 40-11-19 and 40-11-20, filed with the Zoning Administrator on a prescribed form and a filing fee, and reviewed by the seven-member Zoning Board of Appeals.