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Lake County, IL Building Setbacks & Zoning: Lot Coverage Limits (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

Key Facts

AG/RE district cap: 0.10 ISR (10% impervious)
R1 district cap: 0.20 ISR (20%)
R2/R3 district cap: 0.30 ISR (30%)
R4 district cap: 0.40 ISR (40%)
R4A/R5/R6/RR cap: 0.50 ISR (50%)

Summary

Unincorporated Lake County caps impervious surface at 10% to 50% of each lot depending on zoning district, limiting how much of a property can be covered by buildings, driveways, and other hard surfaces.

City-specific rules exist: Waukegan has its own lot coverage limits rules that differ from Lake County's county-level regulations. If you live in Waukegan, check the city-specific page instead.

§ 151.125 DENSITY AND DIMENSIONAL STANDARDS TABLES. The following tables (§ 151.125(1) through § 151.125(5)) establish standards for development in all base zoning districts. ... [2] ISR shall be calculated by dividing the total area of all impervious surfaces on the site by the site's base site area.

Source: Lake County Watershed Development OrdinanceView official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-15: Supplement contains: Local legislation current through Ord. 26-0618, passed 6-9-2026 | State legislation current through ILCS Pamphlet 2025 #5).

Full Breakdown

Lake County Code § 151.125's density and dimensional standards tables set a maximum impervious surface ratio (ISR) for every zoning district in unincorporated Lake County, meaning the share of a lot that buildings, driveways, patios, and other hard surfaces can cover. The cap starts at 0.10 (10%) in the AG and RE districts, climbs to 0.20 in R1, 0.30 in R2 and R3, 0.40 in R4, and tops out at 0.50 in the higher-density R4A, R5, R6, and RR districts. ISR is calculated by dividing total impervious area by the site's base site area, per the section's own formula.

Violations & Fines

Exceeding the maximum ISR for a zoning district violates Lake County Code § 151.125; the county's zoning enforcement can require site plan revisions, deny permits, or order removal of excess impervious surface until the lot complies.

Frequently Asked Questions

What does ISR mean in Lake County's zoning code?

Impervious surface ratio is the share of a lot covered by hard surfaces, roofs, driveways, pavement, calculated by dividing total impervious area by the site's base site area, per Lake County Code § 151.125.

Does this lot-coverage limit apply inside Waukegan or Highland Park?

No. Lake County's zoning chapter, including § 151.125's ISR limits, governs only unincorporated county land; Waukegan, Highland Park, and other incorporated municipalities enforce their own separate zoning codes.

Can the ISR limit be exceeded for solar panels?

Yes, § 151.146(YY)(4) exempts ground-mounted solar panels on commercial solar energy systems from the ISR calculations of § 151.125.

Sources & Official References

[1]Lake County, IL Code of Ordinances (amlegal)

Other rules in Lake County

Noise Ordinances: Construction HoursSome Restrictions Setback RulesSome Restrictions Structure Height LimitsSome Restrictions Parking Rules: Driveway RulesSome Restrictions Fence Regulations: Fence Permit RequirementsSome Restrictions Animal Ordinances: Wildlife Rescue PermitsSignificant Restrictions Animal Ordinances: Pet LimitsSome Restrictions Animal Ordinances: Veterinary Clinic ZoningSome Restrictions

All Lake County rules

Compare Lake County to another location·View the Illinois building setbacks & zoning overview

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Lot Coverage Limits in Cities Across Lake County

Waukegan, IL