Cook County, IL Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- Code
- Zoning Ord. 01-O-30
- Varies By
- Zoning district
- Includes
- Buildings + impervious surfaces
- Stormwater
- MWRD detention applies
Summary
Cook County Zoning Ordinance limits the percentage of lot area that may be covered by buildings and impervious surfaces. Coverage maximums vary by zoning district. Stormwater detention requirements also affect impervious area.
Maximum Impervious Surface (Residential): R1: 20%; R2: 20%; R3: 25%; R5: 50%; R5A: 50%. Floor Area Ratio - Single-Family: R1: 0.10; R2: 0.10; R3: 0.15; R5: 0.25; R5A: 0.40; R6: 0.40; R7: 0.40; R8: 0.40. Multi-Family: R4: 0.50; R5A: 0.50; R6: 0.60; R7: 0.70; R8: 0.80. Commercial Maximum Lot Coverage: C5 Commercial Transition: 40%; C7 Office/Research Park: 30%.
Full Breakdown
The Cook County Zoning Ordinance (Ord. 01-O-30) establishes maximum lot coverage percentages for each zoning district in unincorporated areas. Lot coverage includes all buildings, accessory structures, driveways, patios, and other impervious surfaces. The maximum coverage varies by zoning classification, with lower-density residential districts (R-1) having lower percentages than higher-density districts (R-5). The MWRD Watershed Management Ordinance also affects impervious surfaces through stormwater detention requirements (first inch of runoff from impervious area). Adding structures, driveways, or patios that exceed lot coverage limits requires a variance. The Department of Building and Zoning reviews building permits for lot coverage compliance.
Violations & Fines
Exceeding lot coverage: zoning violation, $100–$1,000 fine. May require removing impervious surface or obtaining variance.
Frequently Asked Questions
How much of my lot can I build on in Cook County?
Do driveways count toward lot coverage?
Sources & Official References
Other rules in Cook County
Compare Cook County to another location·View the Illinois building setbacks & zoning overview
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