Accessory Structures in Lake County, IL (2026)
4 county-level rules, plus city-specific rules for 1 city in Lake County, Illinois.
Verified from official government sources
ADU Rules
In unincorporated Lake County, accessory dwelling units are capped at one bedroom and 1,000 square feet, and only allowed on large AG, RE, E, or R-1 lots.
Lake County ADU Zoning Rules
Some RestrictionsLake County Code § 151.113(D)
Accessory dwelling units (attached to or detached from the principal structure) shall be an allowed accessory use to any allowed detached house use on lots in the AG, RE, E, R-1 Districts with a minimum area of 80,000 square feet or more... Any accessory dwelling unit shall contain no more than one bedroom and no more than 1,000 square feet of gross floor area.
ADU Owner Occupancy
In unincorporated Lake County, the property owner must live in either the main house or the accessory dwelling unit for the ADU to be legal.
Lake County ADU Owner-Occupancy Rule
Some RestrictionsLake County Code § 151.113(D)(3)(a)
The combined total number of individuals that reside in the principal and accessory dwelling units shall not exceed the number that is allowed for a single household... The owner of the real property upon which the accessory dwelling unit is located must occupy either the principal or accessory dwelling unit.
ADU Rental Restrictions
In unincorporated Lake County, an accessory dwelling unit cannot be rented out as a separate income property while the owner lives elsewhere: the property owner must occupy either the principal house or the ADU itself, per County Code § 151.113(D)(3)(a).
Lake County: Owner Must Occupy Home or ADU
Significant RestrictionsLake County Code § 151.113(D)(3)(a)
The combined total number of individuals that reside in the principal and accessory dwelling units shall not exceed the number that is allowed for a single household... The owner of the real property upon which the accessory dwelling unit is located must occupy either the principal or accessory dwelling unit.
Shed & Carport Rules
In unincorporated Lake County, sheds have no size exemption from building permits. Only playhouses and similar structures under 120 square feet skip the permit requirement, so any shed needs a Planning, Building and Development Department permit before construction begins.
Lake County Shed Permit Threshold
Some RestrictionsLake County Code § 150.17 (2024 ICC International Residential Code Amendments, IRC §§ R105.2, R105.5)
Amend item 1, delete with no substitution item #2, 3, and 10. ... Item #1 "Playhouses and similar structures, provided the floor area does not exceed 120 square feet" ... 8. Permits for fences, re-siding, re-roofing, decks, electrical up grade, sheds, detached garages, screen porches and any minor alteration to an existing building that does not exceed 400 square feet are not completed and if a...
Accessory Structures by City in Lake County
1 cities in Lake County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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