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McHenry 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

Building coverage
~30-35% residential/estate
Impervious surface
50% residential
Agricultural coverage
Scales down with lot size
SARA/Class III overlay
Impervious capped at 50%
Authority
UDO Table 16.36-1; § 16.52.040

Summary

In unincorporated McHenry County, maximum building coverage is roughly 30-35% in residential/estate districts and maximum impervious surface is generally 50% (Table 16.36-1). In SARA and Class III resource-area overlays, impervious coverage is capped at 50% regardless of the underlying district.

These county ordinances apply to unincorporated areas of McHenry County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

The maximum impervious surface coverage is limited to the lesser of the maximum impervious surface area allowed in the zoning district or fifty percent (50%), but in no case shall more than fifty percent (50%) of the SARA Overlay District area on site be made impervious.

View official code

Full Breakdown

UDO Table 16.36-1 (§ 16.36.040) sets maximum building coverage and impervious surface by district. Residential and estate districts allow roughly 30% (R-2) to 35% (R-1, E-1) building coverage, with agricultural coverage scaling down as parcel size grows (30% up to 2 acres, 20% for 2-3 acres, 15% for 3-5 acres, 10% for 5+ acres). Maximum impervious surface is 50% in residential/estate/agricultural districts, higher (65-70%) in commercial and industrial districts. In the Special Resource Areas (SARA) and Class III overlays, § 16.52.040 limits impervious coverage to the lesser of the district maximum or fifty percent. Cities set their own coverage rules.

Violations & Fines

Exceeding building or impervious coverage limits is a zoning violation; the county can deny permits, require a variation, or mandate removal of excess coverage, and overlay-area breaches can trigger stormwater enforcement.

Frequently Asked Questions

How much of my lot can I cover with buildings?
In unincorporated McHenry County, roughly 30-35% building coverage in residential and estate districts, with agricultural districts scaling down from 30% to 10% as parcel size increases (Table 16.36-1).
Is there a limit on driveways and patios?
Yes, through impervious-surface limits, generally 50% in residential districts. In SARA and Class III resource overlays, impervious coverage is capped at 50% even if the district would otherwise allow more.

Sources & Official References

Other rules in McHenry County

Fire Regulations: Fire Pits & Backyard FiresLight RestrictionsSetback RulesSome RestrictionsStructure Height LimitsSome RestrictionsParking Rules: Loading ZonesSome RestrictionsAnimal Ordinances: BeekeepingSome RestrictionsAnimal Ordinances: Veterinary Clinic ZoningSignificant RestrictionsFire Regulations: Outdoor BurningSignificant RestrictionsLandscaping Rules: Rainwater HarvestingFew Restrictions

All McHenry County rules

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