ADU Regulations in Illinois: The Complete Guide

Accessory Dwelling Units are gaining popularity across the nation and for good reason! These flexible housing units offer additional space for you and your loved ones plus the possibility of earning additional income through rentals is always there. Plus, the easy accessibility of simply popping into your backyard to enter them is a huge drawing factor. Your property in the Prairie State could be the perfect place for a luxurious modular ADU from Psy Homes. Illinois is becoming more and more friendly towards ADUs, which is great news for many interested homeowners. 

But before starting the process, there are some key rules and regulations to be aware of. Unfortunately, not every Illinois area will permit ADUs. Counties differ in their specific requirements and some counties leave it entirely up to the local jurisdictions to decide. That’s why we gathered all the important information for you to learn about your specific county. Keep reading to find out more!

Are ADUs Allowed in Illinois?

They sure are, although the allowances may vary from county to county. At this time, there are no state-wide regulations for ADUs, which means county and local governments decide the rules. Many counties may not even have requirements, leaving it entirely up to the local level. This can be a blessing in disguise as your municipality may be more open to the possibility of an ADU. Whether you are wishing for a detached ADU, or an attached or conversion unit, you should always check with your local county or municipality authorities for the most clarity. 

The good news is that legislation is currently in process in Illinois for more state-wide allowance for ADUs. This new bill would allow more new ADUs across the state. Since this bill has not passed yet, it is important to stick to the current guidelines, which will be outlined by specific counties below. 

What Is Considered An ADU in Illinois?

In Illinois, an ADU can be defined as “an attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons, is located on a lot with an existing or proposed primary residence, and includes permanent provisions for living, eating, sleeping, cooking, and sanitation on the same parcel as the single-family or multi-family dwelling it is or will be situated on.” 

The modular ADUs from Psy Homes are all built to match these standards with separate kitchen and bathroom facilities plus private bedrooms and living room spaces! 

Can Park Model Tiny Homes Be Used As ADUs?

Yes, certain counties may allow park model homes to be used as an ADU if they meet the permanent housing standards. Park model homes are built to RVIA standards and considered a semi-mobile home so some counties may not consider them a permanent dwelling residence. To be sure, check with your local zoning department. 

Can Log Cabins Be Used As An ADU?

They definitely could! An ADU has to follow certain height and size restrictions, but a smaller log cabin, like one from Psy Homes, could fit the bill. Some of the models start as small as 700 square feet which should be well within the size range for most of Illinois. A rural or unincorporated area of Illinois may be better suited for log cabins as an ADU. 

Can Modern Cabins Be Used As An ADU?

It depends on where you reside, but it is definitely possible! Certain modern cabin models would fit within the Illinois ADU requirements, making them a perfect fit for your ADU. A modern cabin ADU would offer more space and options for long-term rentals. Reach out to your local zoning department to see what they have to say about modern cabins as an ADU. 

What is the Difference Between a Prefab ADU & a Modular ADU?

The key distinction between prefab and modular ADUs lies in how they are constructed and delivered. Prefab units are fully built in a factory and arrive at your property as a complete, single structure that only needs to be placed on-site. Modular ADUs, such as those available through Psy Homes, are manufactured in sections. These modules are shipped separately and then assembled at the property, which allows for more customization during installation and a tighter fit. Illinois does not separate the two with different permitting requirements and both are treated the same under state rules.

What is the Minimum Size for an Accessory Dwelling Unit?

Illinois does not enforce a state-wide minimum square footage for ADUs. Instead, counties and municipalities set their own rules. Most often, local governments require at least 200 to 500 square feet. This gives some flexibility depending on where you live, but you should always confirm with your local zoning office.

Can My ADU be Bigger Than My House?

No, an ADU in Illinois can never outsize the main home on the property. Regulations are designed so that the accessory unit remains secondary in scale. Typically, ADUs can be no more than about 80% of the square footage of the primary dwelling, with some local codes applying a specific upper limit.

How Close To My House Can I Build An ADU?

Setback and placement rules differ by county, but most jurisdictions in Illinois require at least a 5-foot clearance from the rear property line and 3 feet from the side property line. ADUs must also maintain a safe and functional distance from the main residence, generally a minimum of 10 feet but typically not more than 100 feet away.

Do You Need A Permit For An ADU in Illinois?

Yes. All ADUs require permits before construction can begin. At the very least, a building permit is necessary, and depending on the unit’s setup, electrical and plumbing permits are usually part of the process. In some areas, HVAC or environmental health permits may also be required. Each county follows its own process, so it’s important to check locally.

Are There Any Incentives or Grants for ADUs in Illinois?

Currently, there are no Illinois state or federal programs that provide grants, rebates, or other financial support for ADU construction. That said, some municipalities may have local programs, so it’s worth reaching out to your community development or planning department to ask about any available incentives. A city like Chicago has city programs designed to assist ADU homeowners with financial aid and incentives. 

Are Psy Homes’s ADUs Built to Code?

All ADUs from Psy Homes are designed to meet or exceed Illinois building codes. Our team takes care to ensure compliance, so you as the homeowner can be confident your unit will be safe, durable, and fully up to code.

Can an ADU Have Multiple Bedrooms and Bathrooms?

You sure can! Psy Homes offers ADUs in a variety of layouts and you can choose compact one-bedroom units or larger models with two bedrooms and even multiple bathrooms. For example, the Grove ADU includes a two-bedroom, two-bathroom floor plan that works well for couples or small families.

Are ADUs A Good Investment?

Yes, ADUs are often considered a smart investment because of their versatility. They increase property value and can generate rental income through short-term or long-term leasing if permitted in your area. Beyond financial gain, ADUs also provide flexible living arrangements, such as space for aging parents or extended family members. This blend of income potential and personal use makes them a valuable addition to a property.

If you are interested in owning an ADU in Illinois, contact us to learn more or request a free quote for your dream model! 

What Counties in Illinois Allow ADUs? 

Cook County	Cook County Home PageCook County Building & Zoning DepartmentCook County Building Regulations
DuPage County	DuPage County Home PageDuPage County Building & Zoning DepartmentDuPage County Code of Ordinances
Lake County	Lake County Home PageLake County Zoning DepartmentLake County Code
Will County	Will County Home PageWill County Planning & Zoning DepartmentWill County Building Codes
Kane County	Kane County Home PageKane County Building & Zoning DivisionKane County Zoning Ordinance
McHenry County	McHenry County Home PageMcHenry County Planning & DevelopmentMcHenry County Building Codes
Winnebago County	Winnebago County Home PageWinnebago County Building DivisionWinnebago County Planning & Zoning DivisionWinnebago County Codes & Ordinances
Madison County	Madison County Home PageMadison County Building & Zoning DepartmentMadison County Mobile Home Park Code
St. Clair County	St. Clair County Home PageSt. Clair County Building & Zoning DepartmentSt. Clair County Building Regulations
Champaign County	Champaign County Home PageChampaign County Planning & Zoning DepartmentChampaign County Zoning Ordinance
Sangamon County	Sangamon County Home PageSangamon County Building & Zoning DepartmentSangamon County Zoning Ordinance
Peoria County	Peoria County Home PagePeoria County Planning & Zoning DepartmentPeoria County Code of Ordinances
McLean County	McLean County Home PageMcLean County Building & Zoning DepartmentMcLean County Zoning Ordinance
Rock Island County	Rock Island County Home PageRock Island County Building & Zoning DepartmentRock Island County Zoning Regulations
Kendall County	Kendall County Home PageKendall County Building & Zoning DepartmentKendall County Zoning Ordinance
Tazewell County	Tazewell County Home PageTazewell County Zoning Codes
LaSalle County	LaSalle County Home PageLaSalle County Zoning DepartmentLaSalle County Zoning Ordinance
Kankakee County	Kankakee County Home PageKankakee County Code of Ordinances
Macon County	Macon County Home PageMacon County Planning & Zoning DepartmentMacon County Code of Ordinances
DeKalb County	DeKalb County Home PageDekalb County Building Regulations
Vermilion County	Vermilion County Home PageVermillion County Building Department
Williamson County	Williamson County Home Page
Adams County	Adams County Home Page
Whiteside County	Whiteside County Home PageWhiteside County Building & Zoning Department
Grundy County	Grundy County Home PageGrundy County Planning & Zoning OfficeGrundy County Building Codes
Boone County	Boone County Home PageBoone County Building & Zoning DepartmentBoone County Zoning Ordinance
Jackson County	Jackson County Home Page
Ogle County	Ogle County Home PageOgle County Planning & Zoning DepartmentOgle County Zoning Ordinance
Henry County	Henry County Home PageHenry County Zoning & Building DepartmentHenry County Zoning Ordinance
Knox County	Knox County Home PageKnox County Zoning DepartmentKnox County Zoning Resolution
Coles County	Coles County Home PageColes County Regional Planning Department
Macoupin County	Macoupin County Home PageMacoupin County Permits & Zoning InformationMacoupin County Code of Ordinances
Stephenson County	Stephenson County Home PageStephenson County Zoning DepartmentStephenson County Zoning FAQsStephenson County Zoning Ordinance
Woodford County	Woodford County Home PageWoodford County Building & Zoning DepartmentWoodford County Zoning Ordinance
Franklin County	Franklin County Home PageFranklin County Code of Ordinances
Clinton County	Clinton County Home PageClinton County Zoning OfficeClinton County Zoning FAQsClinton County Zoning Code
Marion County	Marion County Home Page
Jefferson County	Jefferson County Home Page
Livingston County	Livingston County Home PageLivingston County Planning & Zoning DepartmentLivingston County Building RegulationsLivingston County Zoning Regulations
Monroe County	Monroe County Home PageMonroe County Zoning & Building DepartmentMonroe County Building Regulations
Effingham County	Effingham County Home Page
Lee County	Lee County Home PageLee County Zoning & Planning OfficeLee County Building RegulationsLee County Zoning Regulations
Christian County	Christian County Home PageChristian County Zoning DepartmentChristian County Zoning CodeChristian County Mobile Home Foundation Ordinance
Bureau County	Bureau County Home PageBureau County Planning & Zoning DepartmentBureau County Zoning OrdinanceBureau County Mobile Home Park Ordinance
Fulton County	Fulton County Home PageFulton County Zoning DepartmentFulton County Zoning Ordinance
Morgan County	Morgan County Home Page
Randolph County	Randolph County Home PageRandolph County Land Resource ManagementRandolph County Code of Ordinances
Montgomery County	Montgomery County Home Page
Logan County	Logan County Home PageLogan County Zoning OfficeLogan County Tiny Home Park Regulations
McDonough County	McDonough County Home Page
Iroquois County	Iroquois County Home PageIroquois County Planning & Zoning OfficeIroquois County Zoning OrdinanceIroquois County Mobile Home Park Ordinance
Saline County	Saline County Home Page
Jo Daviess County	Jo Daviess County Home PageJo Daviess County Planning & DevelopmentJo Daviess County Building CodeJo Daviess County Zoning Regulations
Fayette County	Fayette County Home Page
Jersey County	Jersey County Home PageJersey County Code of Ordinances
Shelby County	Shelby County Home PageShelby County Zoning DepartmentShelby County Zoning Ordinance
Perry County	Perry County Home PagePerry County Building Permit Information
Douglas County	Douglas County Home Page
Crawford County	Crawford County Home Page
Hancock County	Hancock County Home Page
Piatt County	Piatt County Home PagePiatt County Zoning DepartmentPiatt County Zoning Ordinance
Union County	Union County Home Page
Bond County	Bond County Home PageBond County Zoning DepartmentBond County Building CodeBond County Zoning Ordinance
Edgar County	Edgar County Home Page
Warren County	Warren County Home PageWarren County Zoning DepartmentWarren County Zoning Code
Wayne County	Wayne County does not have a government website.
Carroll County	Carroll County Home PageCarroll County Zoning & Building DepartmentCarroll County Zoning Ordinance
Richland County	Richland County does not have a government website.
Mercer County	Mercer County Home PageMercer County Zoning DepartmentMercer County Zoning Ordinance
DeWitt County	DeWitt County Home PageDeWitt County Planning & Zoning DepartmentDeWitt County Zoning Ordinance
Clark County	Clark County Home Page
Lawrence County	Lawrence County Home Page
Moultrie County	Moultrie County Home PageMoultrie County Planning & Zoning DepartmentMoultrie County Zoning Ordinance
Pike County	Pike County Home PagePike County Zoning DepartmentPike County Zoning Ordinance
Massac County	Massac County Home Page
Washington County	Washington County Home PageWashington County Zoning DepartmentWashington County Zoning Ordinance
White County	White County Home Page
Johnson County	Johnson County does not have a government website.
Ford County	Ford County Home PageFord County Zoning OfficeFord County Zoning Ordinance
Clay County	Clay County Home Page
Cass County	Cass County Home PageCass County Zoning DepartmentCass County Zoning Ordinance
Mason County	Mason County Home PageMason County Zoning DepartmentMason County Zoning Ordinance
Menard County	Menard County Home PageMenard County Zoning DepartmentMenard County Zoning Ordinance
Marshall County	Marshall County Home PageMarshall County Zoning DepartmentMarshall County Mobile Home Fact SheetMarshall County Zoning Ordinance
Greene County	Greene County does not have a government website.
Wabash County	Wabash County does not have a government website.
Cumberland County	Cumberland County Home Page
Jasper County	Jasper County does not have a government website.
Hamilton County	Hamilton County Home Page
Schuyler County	Schuyler County Home Page
Brown County	Brown County Home PageBrown County Zoning Codes
Henderson County	Henderson County does not have a government website.
Edwards County	Edwards County does not have a government website.
Putnam County	Putnam County Home PagePutnam County Zoning OfficePutnam County Zoning Ordinance
Stark County	Stark County Home PageStark County Building & Zoning Department
Pulaski County	Pulaski County Home Page
Scott County	Scott County Home Page
Alexander County	Alexander County Home Page
Gallatin County	Gallatin County Home Page
Calhoun County	Calhoun County Home PageCalhoun County Zoning Ordinance
Pope County	Pope County does not have a government website.
Hardin County	Hardin County Home Page

Does Cook County Allow ADUs?

In certain areas, yes! Cook County as a whole doesn’t have a straightforward, countywide ADU regulation, though the City of Chicago which is within the county is piloting ADU policies. Since May 1, 2021, Chicago has allowed ADUs (both interior conversions and coach houses) in five designated pilot areas, within certain zoning districts (such as RS‑2, RS‑3, RT, RM).

However, these are city-specific rules and don’t apply to unincorporated portions of Cook County or other municipalities. There is no clear county-level regulation for ADUs, so if you’re outside Chicago, the rules are unclear. The best next step is to consult the building or zoning department  because local rules or pilot programs may vary.

Does DuPage County Allow ADUs?

Yes, although it is a bit complex. DuPage County appears to permit ADUs only through a Conditional Use process rather than outright by-right. The county’s zoning ordinance includes provisions specifically titled “Requirements for Accessory Dwelling Unit Conditional Use.” In unincorporated areas, the Building & Zoning department handles permits (e.g. accessory structures like sheds, garages) but doesn’t list ADUs as a standard residential accessory use.

So if you’re in DuPage County, plan on applying for a conditional use permit via your local zoning office. Contact the county’s Building & Zoning or Planning & Development department to get guidance on zoning districts, application steps, and any public hearing requirements.

Does Lake County Allow ADUs?

It sure does! Lake County does allow ADUs, with clear limitations. The regulations specify that any accessory dwelling unit must have no more than one bedroom and be no larger than 1,000 square feet in gross floor area.

These units require a building permit, and depending on site conditions, potentially a Site Development Permit as well.  Applications must be submitted in person at the Lake County Central Permit Facility in Libertyville, with site plans, building plans, and other documentation. If you’re considering an ADU there, get in touch with the Planning, Building & Development Department for the specific permit requirements, and they’ll walk you through what’s needed.

Does Will County Allow ADUs?

Yes, Will County does allow accessory dwelling units, referred to as “related living quarters” (interior units) and “ECHO housing units” (attached or detached pre‑manufactured units with removable foundations). Related living quarters are permitted by right in A, E, and R zoning districts, subject to applicable standards. ECHO housing units are allowed with a special use approval in several residential districts (A, E, R‑1, R‑2, R‑2A, R‑3). 

In addition, the county imposes size limits, outlining that ADUs cannot exceed 49 percent of the principal dwelling’s gross floor area (excluding attached garage), or 650 square feet. 

If you’re considering an ADU in Will County, you’ll need to confirm your zoning district and whether your project qualifies as related living quarters or requires a special use permit as an ECHO unit. You should consult the County’s Planning & Zoning department to clarify applicability, zoning standards, and permit steps.

Does Kane County Allow ADUs?

Potentially. Kane County does not have a single, countywide ADU policy, but it does restrict the total area of detached accessory structures, including potential ADUs. On lots of two acres or less, detached accessory buildings cannot exceed a combined total of 900 square feet; on lots between two and five acres, the limit rises to 1,800 square feet.

These regulations apply to detached accessory structures generally, not specifically labeled for residential use. To move forward, you’ll need to verify whether a given structure may be used as an ADU under local zoning, building and subdivision rules. Contact Kane County’s Building, Planning, or Zoning departments to determine if an ADU is allowed and what limitations apply.

Does McHenry County Allow ADUs?

It would appear so. McHenry County provides a framework for ADUs via its Unified Development Ordinance (UDO), which governs land use, zoning, permitting, and building standards in unincorporated areas. The county’s approach to ADUs appears to be subsumed under broader terms like “ancillary dwelling units.” These must comply with building codes and public health requirements especially regarding well and septic systems 

However, the UDO does not detail specific size limits or design standards for ADUs, at least not in the publicly accessible summaries. To move forward, you should reach out to McHenry County’s Planning & Development or Building Codes office to understand how ancillary dwelling units are regulated in your specific location, whether site plan review is required, and how well/septic rules may influence feasibility.

Does Winnebago County Allow ADUs?

It is definitely possible! Winnebago County regulates accessory living quarters: they must be at least 300 sq ft and cannot exceed 900 sq ft.

Setbacks for accessory structures are generally 2.5 feet from rear or side lot lines unless exceptions apply. However, the code doesn’t explicitly clarify whether those accessory living quarters are permitted as full-fledged ADUs; the allowance may depend on zoning district and whether the unit is considered incidental or subordinate. If your plan might exceed standard accessory structure use or if you’re unsure how “living quarters” are treated, go straight to the county’s Planning & Zoning Division for guidance, especially since zoning variations or waivers might apply. 

Does Madison County Allow ADUs?

Madison County’s zoning ordinance defines an Accessory Dwelling Unit as a residential unit within an accessory structure on the same lot as a single-family dwelling.

ADUs cannot exceed 1,000 sq ft. However, other provisions strictly prohibit accessory buildings used as dwellings unless otherwise permitted by zoning and building codes. This indicates ADUs are conditionally allowed only where local zoning explicitly permits them. To proceed, you’ll need to check your zoning district’s specifics or consult the county zoning/ building department to determine whether your property’s location and structure would qualify under ADU rules.

Does St. Clair County Allow ADUs?

There’s no explicit mention in readily available zoning or building code materials of ADUs being allowed in St. Clair County.

Existing ordinances focus on general accessory structures and special uses, for example, accessory buildings must adhere to setback and distance standards, with some uses (like certain accessory buildings) restricted via special use permits. Given this absence of clarity, if you’re considering an ADU, contact the county’s zoning or building official. You’ll need to confirm whether accessory dwellings are permitted at all, what approvals or special uses may apply, and what design or site restrictions you must meet.

Does Champaign County Allow ADUs?

It is really not clear at this moment. Champaign County does not appear to have a countywide ADU ordinance.

However, within the City of Champaign, ADUs were explicitly authorized following the passage of Council Bill 2022‑117 on June 21, 2022, which added Division 9 to the zoning code governing ADUs. The ordinance defines ADUs (detached, attached, or internal), allows one per lot, and sets size limits: maximum 600 sq ft on lots up to 7,200 sq ft; up to 800 sq ft for larger lots. 

If you’re elsewhere in Champaign County or beyond the city limits, you’ll need to consult your specific township or municipal zoning office, since county-level rules don’t seem to include ADUs.

Does Sangamon County Allow ADUs?

Sangamon County does not have a policy or specific provisions in its zoning or building code for ADUs. The County’s Building and Zoning Department administers zoning amendments, variances, conditional uses, accessory structure permits, and building permits among others. 

Given the absence of clear ADU language, if you’re considering an ADU, you should treat it as a special project which will likely require a conditional use petition or zoning amendment. Reach out to the County Building & Zoning Department (they handle variances and conditional uses) to clarify whether ADUs are permitted and under what circumstances.

Does Peoria County Allow ADUs?

It is not very clear as of now. Peoria County’s publicly accessible codes focus on accessory and storage structures like sheds, garages, and carports and the typical ADU use cases are not directly referenced. Residential permits are required for accessory structures exceeding 200 sq ft; anything under that may not require a permit, though setback and size provisions still apply. 

But the code doesn’t clearly identify accessory dwelling units as permitted or regulated. If you’re thinking about using a structure for living purposes, you’ll need to check with the County’s permitting office to see if it’s allowed, or whether the structure will be treated as an incidental accessory or require some form of variance or special use.

Does McLean County Allow ADUs?

It would appear so! McLean County’s zoning code refers to accessory uses—“appropriate, incidental, and subordinate” to the principal use—as generally permitted, and that includes what they call a “guest household unit,” which may feature a separate kitchen. That aligns closely with how many places define an ADU. 

However, there’s no explicit language on size limits, occupancy rules, or separate utility standards for ADUs. It looks like whether such a unit is permitted hinges on the zoning district and approval by the Director of Building and Zoning, but specifics are lacking online.

Your next move should be to contact McLean County’s Building & Zoning or Planning Department to find out if a guest household unit qualifies, whether permits or special uses apply, and what design or utility standards they’d require.

Does Rock Island County Allow ADUs?

Yes! Rock Island County does allow one accessory dwelling unit per residential lot, but there are very clear conditions:

• The ADU must be within a detached structure no larger than 400 sq ft, and must be located in the rear yard.
• Only one ADU is allowed per residential lot, and one of the two units must be owner‑occupied.
• There must be separate cooking and sanitary facilities, separate utility meters (though service may be shared), and an extra parking space beyond what the principal dwelling already requires. 

That’s quite clear. If you’re planning one, make sure your design meets these criteria exactly, then proceed with your zoning and building permit offices.

Does Kendall County Allow ADUs?

Currently, the public zoning ordinance for Kendall County is visible, but there’s no explicit mention of ADUs or accessory dwelling units in the sections available online. 

Your best bet is to reach out directly to Kendall County’s Planning, Building & Zoning Department. Ask whether accessory dwelling units are recognized, and if so, what size, density, or other restrictions may apply. They’d point you to the exact sections of the zoning code or outline the permit path.

Does Tazewell County Allow ADUs?

Yes! Tazewell County permits ADUs in any residential or agricultural zoning district provided the principal use is a single-family dwelling. Only one accessory unit per lot is allowed, it must be owner‑occupied, and cannot be rented to unrelated parties.

The unit must share the driveway and be between 350 and 800 square feet, and if it’s within the main dwelling, its entrance must not face any street the lot fronts. Also, a separate 911 address is required. Reach out to the Tazewell County Zoning Department for the most up-to-date information and permit processes. 

Does LaSalle County Allow ADUs?

It is possible, although not very clear. LaSalle County allows accessory units only through a Special Use process, generally aimed at supporting owners who are elderly or handicapped, or have such relatives. Only one unit per lot is permitted; it must be compliant with building and health codes, and must retain the appearance of a single-family dwelling.

There are also annual affidavit and reconversion requirements, and the Special Use expires under certain conditions such as noncompliance or transfer of ownership. This Special Use process indicates that not all ADUs will be approved, so the best bet is to reach out to the LaSalle County Zoning Office for more information. 

Does Kankakee County Allow ADUs?

Yes, although the regulations are not very clear. Kankakee County’s zoning code allows an accessory dwelling unit or lodging room inside the principal building as an accessory use.  Setbacks for accessory structures apply: minimum 10 feet from the main building and 5 feet from interior lot lines in residential zones. To find out more specific information you will need to contact the Kankakee County Zoning Department. 

Does Macon County Allow ADUs?

Macon County doesn’t explicitly allow accessory dwelling units in the form of regular accessory buildings. If you’re looking to add living space or a separate unit, that kind of structure is generally considered an accessory building but guest houses, servant quarters, apartments, and similar uses are not allowed unless you get a special use permit. Your best move is to contact the Macon County Planning and Zoning Office. Ask them whether your project could qualify for a special use, what the process is, and what standards must be met.

Does DeKalb County Allow ADUs?

It is not certain since there doesn’t appear to be zoning language that defines guesthouses or in-law units. That means there’s a good chance ADUs may either not be addressed or require discretionary review in DeKalb County.

You should reach out to the DeKalb County Zoning or Planning Department directly and ask if accessory dwelling units are allowed or if they would fall under accessory structures. They’ll point you to the exact code section or tell you whether you need to seek a special permit.

Does Vermilion County Allow ADUs?

It would appear so, although the term ADU is not specifically used. Vermilion County’s zoning code does mention “a dwelling unit or lodging room as an accessory use in the principal building,” which suggests that adding an apartment or similar living space inside your home may be okay.

However, because that’s all the public code shows, you’ll want to check with the Vermilion County Building Department to confirm how that’s interpreted in practice, is it allowed, limited by size, or does it require approval? Reach out to them and ask what counts as an accessory dwelling, what approvals are needed, and what rules apply.

Does Williamson County Allow ADUs?

Williamson County doesn’t manage zoning at the county level. That means whether an ADU is allowed is entirely up to your city, town, or village wherever your property sits. So, your next move should be to contact your local municipal zoning or planning department to find out what their rules are and how to apply.

Does Adams County Allow ADUs?

Yes! Adams County explicitly permits ADUs as an accessory use to a single‑family home in any zoning district.

The main exception is in older Planned Unit Developments (PUDs) that were created before these rules and don’t specifically allow ADUs. You can’t sell an ADU separately, it must stay tied to the main house. If you need to know whether your property is within a PUD or what your next steps are, your best bet is to reach out to the “Planner of the Day” at the Adams County zoning office.

Does Whiteside County Allow ADUs?

It is not really clear as Whiteside County’s public zoning documents don’t clearly spell out whether ADUs are allowed. What we do know is that any accessory buildings must meet open‑space rules, which could limit potential ADU development, and that any special use.

Like building something out of the ordinary, would require a formal petition. If you’re exploring an ADU, start by downloading the county’s special use instructions and scheduling a chat with the Building & Zoning Administrator to walk through your plan.

Does Grundy County Allow ADUs?

Yes! Grundy County does allow what it calls “accessory living units,” but there are specific rules you’ll want to know.

The unit must be attached to the main home, either inside it or above an attached garage. The main home needs to be owner‑occupied, and the lot must be at least 6,000 square feet or (.14 acres). The design must keep the appearance of a single-family home, and any new entrance has to be on the side or rear. These units are limited to extended family members, and if they move out, approval expires, requiring a new permit. 

To move forward, get in touch with the Grundy County Planning & Zoning, they’ll walk you through design standards, permit requirements, and help you with applications. 

Does Boone County Allow ADUs?

Boone County’s zoning code doesn’t explicitly address accessory dwelling units.

Instead, it treats accessory structures, like sheds or garages, based on zoning district rules, and there’s no mention of guest units or apartments.

Since each district lists what’s allowed by right or as a special use, your best bet is to go straight to the source and contact the Boone County Zoning or Building & Zoning Office. They can tell you whether ADUs are allowed in your area, whether you’d need a special use permit, and what steps to take next. 

Does Jackson County Allow ADUs?

Jackson County’s publicly available documents aren’t very clear on ADUs, but they do include general standards for accessory dwellings such as size limits (no more than 1,000 square feet), where the unit can sit (must be in the rear yard if detached), and rules about ownership and design. That said, these seem more like guidelines than a standalone ADU policy.

Your next step should be to reach out to Jackson County’s Planning or Building Department. Ask them specifically whether ADUs are recognized as a permitted use or require conditional approval, what size or design limits apply, and how to submit a permit or application.

Does Ogle County Allow ADUs?

It is not really clear. Ogle County defines accessory buildings and uses quite broadly, but its rules don’t specifically mention ADUs or living quarters. Instead, the code only offers general limits for accessory buildings. Because nothing directly addresses ADUs, your next best move is to reach out to the Ogle County Planning & Zoning Department. Ask whether ADUs are allowed in your zoning district, whether they’d be considered accessory buildings, and what you’d need to submit like plans, permits, or possible variance requests.

Does Henry County Allow ADUs?

Henry County’s zoning and building services division administers land-use activities but doesn’t have any clear provision for ADUs in its published documents.

That doesn’t mean ADUs aren’t possible, but it does mean the rules aren’t spelled out. To get clarity, contact the Henry County Zoning & Building Officer to ask whether accessory dwellings are permitted, and what steps you should follow next. 

Does Knox County Allow ADUs?

No. Knox County is more direct than other Illinois counties. Accessory buildings are not allowed to be used for dwelling purposes That suggests ADUs, detached or otherwise, aren’t permitted under current county rules. Still, if you’re serious about pursuing one, you can reach out to the Knox County Zoning Department for confirmation or to ask whether there’s a path via variances or special use requests.

Does Coles County Allow ADUs?

Coles County doesn’t operate under a county zoning framework which means there’s simply no zoning or permitting at the unincorporated level. That means whether you can build an ADU will depend on the rules of your city, village, or township. Your next step is to reach out to your local municipal building or zoning office, the county itself won’t have a say, so the local municipality is where you’ll get the guidance you need.

Does Macoupin County Allow ADUs?

Similar to Coles, Macoupin County doesn’t have zoning in unincorporated areas. So again, whether an ADU is allowed depends entirely on local municipal rules if you’re inside city or village limits. Start by identifying your municipality, then contact its planning or zoning department to ask how ADUs are handled. The county won’t be able to approve or advise on your project directly.

Does Stephenson County Allow ADUs?

No. Stephenson County’s zoning ordinance strictly limits you to one dwelling unit per lot, regardless of size or zone.

That means adding another full kitchen-equipped unit, whether inside your home or in an accessory structure, would violate the rule. If you’re serious about exploring an ADU, the only path forward may be applying for a variance or conditional use permit. Your next stop should be a conversation with the Stephenson County Building & Zoning Department to see what flexibility there is, what forms are needed, and how to apply.

Does Woodford County Allow ADUs?

Woodford County doesn’t specifically address ADUs in its zoning code, but that doesn’t leave you hanging.

Instead, the county treats things like guest homes or granny flats under its broader accessory building rules. Since nothing’s spelled out as ADUs, the best move is to connect with the County’s Building & Zoning office. Ask them whether an accessory dwelling unit might be treated as a special use or variance, what paperwork you’ll need, and how these sorts of structures are handled based on your property’s zoning.

Does Franklin County Allow ADUs?

Like Woodford County, Franklin County’s code doesn’t mention ADUs by name in the publicly available sections. If you’re thinking of adding a separate living space, like a basement apartment, in-law suite, or garage unit, you’ll need to reach out to the Building & Zoning Department. They’ll tell you if that counts as an accessory dwelling, whether a special permit or conditional use is needed, or if you might need to apply for a variance. 

Does Clinton County Allow ADUs?

No. Clinton County makes it crystal clear that accessory structures cannot be used as dwellings in any zoning district.

That rules out detached units, garage apartments, or guest houses meant for living. If you still want to explore your options, maybe a conversion of existing space or structure, you’ll need to contact the Zoning Department and ask whether there’s any flexibility, like a text amendment, special use, or exception that could apply.

Does Marion County Allow ADUs?

Marion County doesn’t appear to have any publicly available rules or permits for ADUs under its county-level zoning or building code.

That means the county itself might not regulate them at all. The best next step is to reach out directly to the Marion County Zoning Office and their team can tell you whether ADUs are recognized, what regulations might apply if there are any, and which documents or permits you’d need to move forward.

Does Jefferson County Allow ADUs?

Unfortunately, Jefferson County’s publicly accessible county code doesn’t reference ADUs or housing accessories to a single-family home.

That suggests they may not have a formal ADU policy. The most practical approach is to contact the county zoning or planning office and ask specific questions: Is an ADU allowed? Does it require a conditional use or variance? What do your zone district rules say? That’s how you’ll find clarity and your next steps.

Does Livingston County Allow ADUs?

Like some other Illinois counties, Livingston County’s zoning code covers general accessory buildings with basic rules such as where accessory buildings belong and how close they can get to property lines. But ADUs don’t appear to be explicitly covered. Your next move is to reach out to the Livingston County Regional Planning & Zoning Office, explain what you’re planning, and ask whether ADUs are allowed, if they fall under accessory use, or if you’d need a special use permit to move ahead.

Does Monroe County Allow ADUs?

Monroe County doesn’t use the term “ADU” in its county code, but the municipal code for Monroe (a different jurisdiction) actually allows accessory dwelling units in single-family residential zones, provided the lot meets minimum size requirements.

That doesn’t necessarily apply to the county level. For the county, your best move is to reach out to the Monroe County Zoning & Building Office, where Chris Voelker, Zoning Administrator, can walk you through whether ADUs are allowed in your area of the county, what rules might apply, and how to get permits if you’re looking to move forward

Does Effingham County Allow ADUs?

Effingham County doesn’t control zoning in unincorporated areas; instead, all zoning and building rules are managed at the municipality level.

What that means is ADU rules will vary depending whether you’re in Effingham city, Altamont, Teutopolis, or elsewhere. Start by identifying your city or village, then contact their local planning and zoning department, like the City Planner in Effingham, to ask if ADUs are allowed and how to apply

Does Lee County Allow ADUs?

Lee County’s zoning code doesn’t say anything specific about ADUs and the focus is on defining zones and permitted land uses without mentioning accessory living units. Your best bet is to reach out to the Lee County Building & Zoning Office. They’re the ones who can tell you clearly what your property’s zoning allows and whether an ADU might be considered under accessory uses or require a special approval.

Does Christian County Allow ADUs?

Christian County does have a zoning code that covers development outside municipalities like Taylorville and Pana. but the public documents don’t mention ADUs or accessory dwelling units specifically.

Since there’s no clear pathway or rule spelled out for guest units or granny flats, your best bet is to get in touch with the Christian County Zoning or Planning Department. Ask them if ADUs are permitted, whether you’d need a conditional use permit, and what the site or zoning requirements might be. They’ll steer you right.

Does Bureau County Allow ADUs?

Bureau County has a full zoning system that covers residential, agriculture, subdivisions, floodplain rules, and all that, but there’s no mention in the code of ADUs.

That means if you’re planning on adding a separate living unit, you’ll need to seriously check with the Bureau County Planning & Zoning Department before you do anything. They’ll tell you whether ADUs are seen as accessory structures that are allowed, or if you’ll need to file for a conditional use or variance. It’s the surest way to know what your next step should be.

Does Fulton County Allow ADUs?

No. Fulton County makes a pretty clear rule in its zoning ordinance that accessory buildings must not be used as dwellings. In other words, you can’t convert a shed or build a small guest unit and call it living space. If you’re hoping to do something like that, the county’s stance is no, unless there’s a longer, formal exception or amendment process.

Your best move? Contact the Fulton County Zoning Office, lay out your idea, and ask if any route for special approval or code change exists.

Does Morgan County Allow ADUs?

Yes! Morgan County clearly allows ADUs, both inside your main home and as detached units, with some sensible ground rules.

Internal units must meet building and health codes, have proper permits, and stay under 75% of your home’s square footage (with a minimum of 400 sq ft) If you’re thinking about a detached ADU, you’ll need approval from the zoning administrator, follow existing lot coverage and setbacks, live in one of the units, and the style of the ADU should match your main house. Parking also needs to align with residential standards, and the ADU can’t be used as a short-term rental. 

Your next step is to reach out to Morgan County’s Planning & Zoning or Building department and ask about the “accessory dwelling standards” in your zoning district. They’ll help you determine what’s allowed, what paperwork to fill out, and how to get a building permit started.

Does Randolph County Allow ADUs?

Randolph County doesn’t explicitly mention ADUs in its county zoning material. Since there’s no detailed guidance online, any accessory dwelling would likely fall into a gray zone.

Your best move is to contact the Randolph County Land Resource Management Division (which handles zoning, conditional uses, and permits) and ask directly whether ADUs might be considered accessory structures or if they’d need a special or conditional use permit.That way, you’ll know exactly what rules apply, whether you need a hearing, and what steps to take if your neighborhood allows flexibility.

Does Montgomery County Allow ADUs?

Following the pattern of multiple Illinois counties, Montgomery County doesn’t regulate ADUs at the county level and zoning and building rules are handled by each town, village, or city individually. That means whether you can add an ADU depends entirely on your specific municipality’s code. Your next step is to identify which municipality your property is in, say, Litchfield, Hillsboro, or any village, and contact that local Planning & Zoning office. They’ll tell you if ADUs are allowed, whether you’ll need a special permit, and what design or application requirements apply. 

Does Logan County Allow ADUs?

There aren’t any direct references to ADUs in Logan County’s zoning code, but the ordinance does outline accessory building rules like setbacks (minimum 5 feet) and building size requirements within certain residential districts .

Since ADUs aren’t explicitly mentioned, your safest next move is to reach out to the Logan County Zoning or Planning Department. Ask them directly whether dwellings accessory to a single-family home are allowed, whether a special or conditional use permit is required, and what applications or documentation you’d need to file.

Does McDonough County Allow ADUs?

McDonough County-based guidance for ADUs seems absent or not publicly accessible online. That puts your ADU project square within local municipal control since rules often differ city to city. Identify your specific municipality (like Macomb or others), then contact its local planning or zoning office. Ask whether ADUs are permitted, how they’re regulated, and how to kick off the zoning or permit process for your proposed project.

Does Iroquois County Allow ADUs?

Iroquois County’s zoning ordinance doesn’t explicitly regulate ADUs, but it does require additional parking when adding dwelling units to a property. That’s a clue that accessory units could be considered as part of the “increase in intensity of use.”

To get clarity, your next step should be to contact the Iroquois County Planning & Zoning Office to ask if adding a secondary living unit is allowed, how it would be treated under zoning rules, whether a conditional use permit is needed, and what the parking or site requirements would be.

Does Saline County Allow ADUs?

There’s no mention of accessory dwelling units in Saline County’s zoning documents or online resources but what we do see are general building and permitting processes (like when a building permit is needed for a structure over 10 × 12 feet).

That means whether you can add a small apartment or granny flat likely depends on your local municipality or township rules. The clearest path forward is to contact the Saline County Planning & Zoning Department and ask directly: is an ADU considered an accessory structure under your zoning, and if so, what permits or standards apply?

Does Jo Daviess County Allow ADUs?

Yes! Jo Daviess County allows detached ADUs, but they come with pretty clear rules. The unit must sit on at least a 5-acre lot, be between 400 and 900 sq ft, located no more than 150 feet from the main house, share existing driveways and utilities (though separately metered), and cannot be used for guest accommodations, all via a special use permit that expires in three years unless renewed. If you’re interested in pursuing one, reach out to the Jo Daviess County Planning & Development Department, ask about the special use permit process for ADUs, and how to apply.

Does Fayette County Allow ADUs?

It is not clear, although it may soon be clearer. There’s evidence that Fayette County has been working on an ADU Zoning Ordinance Text Amendment (ZOTA), which would limit ADUs to only attached units or conversions of existing structures but not allowing brand-new detached units.

That suggests ADU policy is in flux at the county level. To figure out exactly where things stand today, your best next move is to reach out to the Fayette County Planning or Zoning Department, ask whether the ZOTA has passed, and what types of accessory dwelling units might now be permitted. 

Does Jersey County Allow ADUs?

Jersey County’s code leans heavily on the 2018 International Residential Code for building rules and not on ADU-specific language. It covers basic permitting and building safety but doesn’t mention accessory dwelling units or granny flats anywhere in the ordinance summaries or building code.

Since nothing is spelled out, your next best step is to contact the Jersey County Code Administrator or Building Department. Ask if an ADU could be treated as a permitted accessory structure or if it would require a special permit and request guidance through their permit process.

Does Shelby County Allow ADUs?

It is unknown. Shelby County’s zoning materials don’t flag ADUs directly, but they do enforce permitting for all new buildings, including accessory ones—like garages or sheds. What the code doesn’t say leaves the door open: an ADU might be allowed if considered an accessory building or it might need special review. Your best next move is to speak with Scott McKee, the Zoning Administrator, at the Shelby County Zoning Office. Ask if accessory dwelling units are considered under accessory building rules or if you’ll need a conditional use permit. They’ll guide you on filings, permits, or zoning applications required.

Does Perry County Allow ADUs?

Maybe but it is not clear right now. Perry County’s zoning ordinance defines what a “dwelling unit” is but doesn’t say anything about having more than one unit per single-family lot or allowing accessory units. The code doesn’t clearly allow or disallow ADUs. To find out for sure, reach out to the Perry County Zoning Department. Ask if you can build a secondary living unit on a property, what counts as a dwelling unit, and whether it would require a variance, conditional use, or any special approval.

Does Douglas County Allow ADUs?

Douglas County’s publicly available documents don’t clearly define or mention ADUs.

The county does cover building permits and notes requirements such as notifying the Health Department about well and septic changes if bedrooms are added. Since the county doesn’t clearly address ADUs, your best next move is to contact the Douglas County Building & Zoning Department or Highway Department. Ask whether a secondary living unit is allowed under current rules, whether it would require a variance or special approval, and what forms or applications you’d need to fill out.

Does Crawford County Allow ADUs?

There don’t seem to be any references to ADUs or accessory dwelling units in Crawford County’s zoning materials or online resources. That likely means the county doesn’t have a clear policy in place. The most straightforward step is to reach out to the Crawford County Zoning or Planning Office directly. Ask whether ADUs are recognized as a permitted accessory use, whether you’d need a conditional or special use permit, and what the application process looks like in practice.

Does Hancock County Allow ADUs?

Hancock County’s zoning code states that accessory uses and structures must be on the same lot as the main building and require a permit but the rules are aimed at things like storage, not living units. That suggests that living spaces such as granny flats or ADUs aren’t clearly contemplated. Your next best step is to reach out to the Hancock County Zoning Office and ask whether accessory dwelling units fall under accessory structures or if they’re disallowed, plus whether any special permissions or hearings would be required to build one.

Does Piatt County Allow ADUs?

It is not very clear at this point. Piatt County’s zoning ordinance focuses on building types, uses, and parking requirements but doesn’t specifically mention ADUs or accessory dwelling units. The best path forward is to contact the Piatt County Zoning Department, ask if living units separate from the main house are allowed, how they’d be defined or permitted, and whether they’d trigger building permit requirements or special reviews.

Does Union County Allow ADUs?

Yes, Union County does allow accessory dwelling units but only under specific conditions. ADUs are permitted only in residential zones (R1–R4), and the property must be at least two acres, have an existing single-family dwelling, be served by the local fire protection district, and be free of code enforcement issues. If you meet those criteria, moving forward means contacting the Union County Zoning or Planning Office to confirm if your property qualifies and to understand the permit application, hearing, or approval process.

Does Bond County Allow ADUs?

No, they are not allowed. Bond County’s zoning code is crystal clear that accessory structures cannot be used as dwellings in any zoning district, and using one that way, even temporarily, requires removal unless it’s in agricultural use tied to family. Since the rules are explicit, your next move if you’re hoping to add a secondary living space is to contact the Bond County Zoning Department. Ask if there’s any exception or special use path, though current rules strongly suggest none exist.

Does Edgar County Allow ADUs?

Edgar County doesn’t have widely published zoning rules regarding ADUs and its available documentation is focused on solar and wind use, not housing or accessory dwellings.Your next step: reach out to the Edgar County Zoning or Planning Office. Ask if secondary living units are permitted, whether they fall under accessory structures, and what review or permit process would apply if they’re allowed.

Does Warren County Allow ADUs?

Warren County’s zoning code doesn’t mention accessory dwelling units or living uses in accessory structures, but it does limit properties to just one main building per lot in general.That means an accessory unit might not be permitted in most cases. To be sure, contact Mark Shallenberger, the Warren County Zoning Officer and he can clarify whether ADUs are allowed, or if a variance or conditional use might be an option.

Does Carroll County Allow ADUs?

Carroll County’s zoning ordinance doesn’t mention accessory dwelling units in the publicly available sections. The county code outlines zoning districts, allowed uses, and the process to amend zoning, implying strict conformity.Your next best step is to connect with the Carroll County Zoning & Building Department. Ask if ADUs are recognized under “accessory uses,” and whether a special zoning amendment or appeal would be needed to add one.

Does Richland County Allow ADUs?

Richland County doesn’t offer zoning ordinance details on its website, so there’s no clear public information on whether ADUs are permitted or regulated. For clarity, contact the Richland County Zoning or Planning Department directly. Ask whether accessory living units are allowed and what zoning or permitting steps you’d need to follow to add one. Because there is no government website for Richland County, you will need to call them at (618) 392-3111 to talk with Amanda Troyer, the current County Clerk, or simply visit in person. 

Does Mercer County Allow ADUs?

Mercer County’s zoning code talks about “one main building together with its accessory buildings” and outlines definitions for accessory structures, but doesn’t specifically mention accessory dwelling units (ADUs) or separate living spaces. Because ADUs are not clearly addressed, the best move is to reach out to the Mercer County Zoning Department, explain what you’re considering, and ask whether an ADU might qualify as an accessory structure, or if a special permit or variance would be required to build one.

Does DeWitt County Allow ADUs?

Perhaps, but it is not confirmed as of now. DeWitt County’s zoning ordinance permits accessory structures in any district and common examples include garages or utility sheds.Since ADUs aren’t explicitly mentioned, it’s hard to know whether living units would fall under that category or require additional approval. Your next step should be to contact the DeWitt County Planning & Zoning Department and ask if accessory dwelling units are allowed, and whether you’d need a conditional use permit, variance, or similar approval before moving forward.

Does Clark County Allow ADUs?

Clark County doesn’t have clear ADU-related information visible in its publicly available zoning resources, and the county website doesn’t provide zoning details beyond general permit information.Without a clear reference, the safest path is to reach out to the Clark County Building or Zoning Department, lay out your ADU idea, and ask whether they’re allowed under accessory use rules or if you’d need special approval or a conditional use permit to proceed.

Does Lawrence County Allow ADUs?

Yes and no. Since that’s unclear, let’s break it down. Lawrence County’s zoning code includes a category called “Guest House” .  Here’s how it works: it’s allowed only with a special use permit in specific zones (like A‑1, A‑2, PF, RR, and SRD) and requires a minimum lot size of 3 acres.

It also can’t exceed 50% of the primary dwelling’s living area or 1,000 square feet, must be no more than 45 feet from the main home, and can’t be rented or used year‑round, only up to 180 days per year.

Utilities must tie into the main house, and architectural designs must match. If that sounds close to what you’re planning, your next move is to reach out to the Lawrence County zoning office to ask about the guest house options, the special use permit process, and whether your property meets the requirements.

Does Moultrie County Allow ADUs?

Moultrie County’s zoning code defines “accessory buildings” as structures incidental to the main building but it doesn’t explicitly say whether those buildings can be used as living units.

The regulations require that accessory buildings must come after the principal one is built. Since there’s no clear guidance one way or another, your next move is to reach out to the Moultrie County Planning & Zoning Department. Ask them if ADUs are permitted, how they’re treated under accessory-use rules, and what permitting process applies. Kristi Hart, the Planning & Zoning Director, could help walk you through the process.

Does Pike County Allow ADUs?

It is not really clear at this point. Pike County’s publicly available zoning materials do not directly address accessory dwelling units.

They do, however, include building permit fees for accessory structures and outline how to request conditional uses and zoning amendments. That suggests ADUs may require special approval. Your best next step is to contact the Pike County Zoning Administrator to ask whether an accessory living unit is allowed, what paperwork or conditional use process would apply, and whether there are design, size, or occupancy rules you should plan around.

Does Massac County Allow ADUs?

There aren’t any clear public references to accessory dwelling units in Massac County’s zoning or building code materials. To find out whether ADUs are allowed, whether they’re treated as accessory uses, or if a variance or special permit is needed, your next step is to reach out to the Massac County Zoning or Building Department. Explain what you’re hoping to do, and ask for guidance on the permitting path. 

Does Washington County Allow ADUs?

Right now, Washington County has not formally allowed ADUs across its rural areas. However, officials are actively exploring the idea (public input is open until August 22, 2025) to potentially permit them in non-farming zones under new rules that align with recent state law changes. If you’re watching this space or hope to add an ADU, your next best step is to reach out to the Washington County Department of Land Use & Transportation, ask whether your property might be included in the pilot proposal, and find out how to submit feedback or weigh in before the deadline.

Does White County Allow ADUs?

White County doesn’t publish detailed ADU or zoning code information online, it mostly shares general county government resources, without clear guidance on accessory living units. That doesn’t mean they’re off the table, it just means the rules aren’t posted publicly. A good next move is to contact the White County Zoning or Planning Department directly, explain your idea, and ask whether ADUs are treated as permitted accessory uses or whether you’d need to apply for special approval or a variance to proceed.

Does Johnson County Allow ADUs?

There appears to be no available public information on ADU rules in Johnson County.  Your best bet? Contact the Johnson County planning or zoning office, and ask if accessory dwelling units are allowed, how they’d be regulated, and what steps you’d need to take. There is no government website for Johnson County so you will need to visit them in person or call the County Clerk at 618-658-3611 for more information. 

Does Ford County Allow ADUs?

No. Ford County’s zoning ordinance is explicit that accessory buildings are not allowed to be used for dwelling purposes. That means garage apartments, granny flats, or any secondary living structures are off-limits under current rules. If you’re hoping to pursue one, you’ll still want to reach out to the Ford County Zoning Office to double-check and ask whether any variance or special use process might offer a path forward.

Does Clay County Allow ADUs?

There aren’t any countywide regulations for Clay County when it comes to ADUs. If you’re within Clay County, your ADU chances hinge entirely on whether you’re in a municipality that regulates ADUs. The most efficient next move is to contact the Clay County zoning or planning office, or your local city or village planning department, and simply ask whether ADUs are allowed on your property and what the permit process looks like.

Does Cass County Allow ADUs?

Cass County’s zoning framework covers everything from setbacks to lot sizes across its unincorporated areas but there’s no explicit mention of accessory dwelling units or secondary homes. To get a straight answer, reach out to the Cass County Zoning Officer and ask whether living units in accessory buildings are allowed or if a special use or variance is required.

Does Mason County Allow ADUs?

It sure does! Mason County does allow ADUs, and the rules are surprisingly detailed. Only one ADU is allowed per lot. The owner must live in either the main home or the ADU.

The unit must be between 720 and 1,000 square feet (never larger than the main house) and must connect to proper water and sewer systems. It also needs parking, matching design, and placement close to the principal dwelling. You must file deed restrictions to ensure compliance and prevent separate sale. If you’re interested, head to the Mason County Zoning Office and ask about the permit and review process.

Does Menard County Allow ADUs?

It isn’t certain because Menard County doesn’t publicly spell out ADU rules, and no clear references to them show up in available documentation or zoning summaries. That said, this kind of zoning question is exactly what your Menard County Zoning Administrator is there to answer. Reach out, explain your idea, and ask whether ADUs are currently allowed or if they’d require a special use, variance, or text amendment to proceed.

Does Marshall County Allow ADUs?

Yes! Marshall County has a clear definition for ADUs. In their zoning ordinance, a “Dwelling, Accessory” is defined as a separate dwelling located on the same parcel as the primary residence and owned by the same person, and it must meet all requirements of a Single-Family Dwelling. That means ADUs are explicitly allowed, so if you’re thinking about building one, your next step is to reach out to the Marshall County Zoning Department.

Ask how ADUs are treated under your zoning district, what required permits or approvals are needed, and how to start your application. You can connect with Zoning Administrator Ryan Giacometti to walk through the specifics. 

Does Greene County Allow ADUs?

There are no zoning rules or public documentation about ADUs in Greene County, Illinois available online. That lack of clarity means we don’t know if accessory dwelling units are even recognized or permitted. Your best move is to reach out directly to the Greene County Planning or Zoning Office and explain your idea. Ask whether ADUs are allowed under current rules, or if it’s considered an accessory structure needing a special permit or variance. They’ll guide you on what steps to take from there.

Does Wabash County Allow ADUs?

There’s no clear mention of accessory dwelling units in Wabash County’s  publicly available zoning resources. That likely puts ADUs in a gray area. To get clarity, you’ll want to connect with the Wabash County Zoning or Planning Department, explain what kind of secondary living space you’re hoping to add, and ask whether ADUs are recognized as allowed uses, or if you’d need a conditional use permit or variance. That conversation will tell you exactly what your path forward looks like. Because there is no government website for this county, you will need to either call them at 618-262-5362 or visit them in person. 

Does Cumberland County Allow ADUs?

Maybe, but it is unknown as of now. Cumberland County doesn’t explicitly address accessory dwelling units in its zoning or comprehensive plan materials. While there are discussions around land use, code enforcement, and improving building permit processes, ADUs aren’t specifically mentioned. Your best next move is to reach out to the Cumberland County zoning or planning department (or the building permit office) to ask if ADUs are allowed as accessory structures, and if so, what permit or review process you’d need to follow.

Does Jasper County Allow ADUs?

No. Jasper County’s code states that accessory uses like sheds and garages are generally permitted but it prohibits the use of any accessory structure as a dwelling throughout the county. So, under current rules, ADUs are not allowed. To move forward or explore potential exceptions, you’ll want to contact the Jasper County Zoning Administrator and ask if there’s any path through variance or special use to allow an ADU. There is no government website for Jasper County so you will have to visit them in person or call the county office at 618-783-2915. 

Does Hamilton County Allow ADUs?

Yes! Hamilton County allows ADUs in any zoning district that permits single-family detached homes, with the exception of the rural A‑1 Agricultural District.

You can only have one ADU per lot, the property owner must live in either the main house or the ADU, and the unit cannot be used as a short-term rental. There are also limits on size (800 sq ft max), height (24 ft or 2 stories max), location, and sewer connections. To move ahead, contact the Hamilton County Planning or Zoning Office, ask whether your property qualifies, and get the application steps and permit details.

Does Schuyler County Allow ADUs?

It is not known at this time. There are no direct references to ADUs or accessory dwellings in Schuyler County’s online zoning or planning documents. That typically means the county hasn’t made a clear provision one way or the other. The most effective next step is to get in touch with the Schuyler County Zoning or Planning Department or even the County Clerk’s office in Rushville. Ask whether ADUs are allowed under current zoning, whether you’d need a special use permit or variance, and what the application process looks like. They’ll give you the straight story.

Does Brown County Allow ADUs?

Brown County doesn’t administer a unified zoning or ADU policy at the county level; instead, municipalities within the county typically set their own rules. That means whether ADUs are allowed depends on whether you’re in a city or village that regulates them. A good next move is to contact the Brown County Zoning Officer, Dave Mayes, who handles zoning and permit matters for unincorporated areas. Ask how accessory dwellings are treated under the zoning ordinance and whether they’re permitted, or if special permits or hearings are required to add one.

Does Henderson County Allow ADUs?

There isn’t any available public documentation mentioning ADUs for Henderson County and there is no government website for Henderson County to find out more information. That likely puts it in a gray area, untested and undefined. To get a clear answer, reach out to the Henderson County Zoning or Planning Office. Ask if accessory dwelling units are recognized as permissible use and if you would you need a special use permit or zoning variance. That conversation should give you the clarity you need. 

Does Edwards County Allow ADUs?

No. Edwards County is firm: using any accessory structure as a dwelling is strictly prohibited across zoning districts. That means garage conversions or granny flats simply aren’t allowed under current rules. If you’re hoping to create a secondary living space, your next move should be to reach out to the Edwardsville zoning or planning office to confirm how rigid that rule is and whether any path exists through special uses or amendments. Since there is no government website, you will need to visit them in person or call the county office at 618-262-4466. 

Does Putnam County Allow ADUs?

Yes! Putnam County’s zoning ordinance does acknowledge something called an “Accessory Housing Unit” as a secondary dwelling on the same lot or within a single-family home, complete with independent living facilities. However, the finer details like whether rentals are permitted, allowed size, or approval process, etc., aren’t fully in the public summaries. This means you will need to reach out to the Putnam County Zoning Department, ask if ADUs are allowed in your zoning district, and request clarity on rules, permit steps, and whether a zoning board hearing is required.

Does Stark County Allow ADUs?

Maybe, but it’s not clear right now. Stark County’s zoning rules define accessory buildings generically but they don’t say whether those buildings can be used as dwellings. The default position likely doesn’t allow living space in accessory structures unless the county zoning office says otherwise. Your best move is to call or visit the Stark County Zoning & Planning Office, explain what you’re thinking, and ask whether ADUs are allowed, what permit path you’d follow (variance or special use), and what fees or review process you’d face. 

Does Pulaski County Allow ADUs?

It is uncertain. Pulaski County‘s zoning materials focus on general development, land use structure, and some regulations like solar installations but they don’t include any mention of ADUs, accessory dwellings, or granny flats. That means ADUs are either not specifically addressed or may fall into a gray area, which could vary depending on local township or municipal rules. To get a clear answer, your next move is to contact the Pulaski County Planning & Zoning Department and ask whether accessory living units are permitted, if they fall under accessory structure definitions, or if you’d need a variance or special permit to proceed.

Does Scott County Allow ADUs?

Like some other Illinois counties, Scott County’s website provides information on county governance and public services, but it doesn’t include zoning or planning ordinances and there isn’t any publicly posted zoning code that addresses ADUs either. That means the regulations remain unclear for now. Your best next step is to contact the Scott County Clerk’s office for guidance. Ask if accessory dwelling units are permitted in your area, whether they’re defined under accessory structures, and what application or approval path you’d need to follow.

Does Alexander County Allow ADUs?

It is not certain either way. Alexander County’s publicly available documents are focused on long-term hazard planning and don’t include zoning or ADU-related regulations. That means the question of whether ADUs are allowed is unresolved online. Your next step should be to reach out to the Alexander County Zoning or Planning Department, explain what you’re trying to do, and ask whether accessory living units are permissible, and if so, what code section or permit is required. They’ll steer you in the right direction.

Does Gallatin County Allow ADUs?

Yes, it would appear so. Gallatin County’s zoning rules are slim, but a staff report defines “Dwelling Unit, Accessory” as a separate unit located either within the main home or an accessory building. This suggests that ADUs are recognized in some form, although it’s not clear what zoning districts or standards apply. Your best next step is to reach out to the Gallatin County Zoning or Planning Department, ask how they interpret that definition, and whether ADUs are allowed by right or require conditional approval. Let them guide you through what’s needed.

Does Calhoun County Allow ADUs?

It is unclear since Calhoun County appears to lack a formal zoning system altogether, it’s indicated that much of the land is unzoned and there’s no zoning text to analyze. Since that leaves ADUs in a gray zone, your most reliable next step is to contact the Calhoun County Building Inspector or relevant county office. Explain your ADU idea and ask whether such a unit would need building permits, special review, or compliance with other standards. They’ll help you figure out what applies locally.

Does Pope County Allow ADUs?

There is no county website or any public zoning code for Pope County, which makes rules around ADUs extremely murky. The absence of public documents means the best path forward is to go directly to local resources. Your next step should be to contact the Pope County Clerk’s office or county administration to ask if any local planning or zoning regulations exist for ADUs, whether they’re permitted as accessory structures, and what the application or approval process would look like if available.

Does Hardin County Allow ADUs?

Hardin County’s zoning system is fairly comprehensive, organized into multiple zoning districts like R-1 (single-family residential), R-2 (multi-family), commercial, industrial, and so on, and each district has its own list of permitted, conditional, accessory, and prohibited uses. That means whether an ADU is allowed depends heavily on which zoning district your property falls under, and whether an ADU is explicitly listed as an accessory use or requires conditional approval. At this point, there are no county-wide regulations governing ADUs. 

The county’s 2009 Development Guidance System Zoning Ordinance provides the full breakdown. Since ADUs aren’t obviously defined or highlighted in the publicly accessible summaries, your next best move is to reach out to the Hardin County Planning & Zoning Department. Explain what you’re considering whether it is a small attached or detached living unit and ask about specific requirements. 

Accessory Dwelling Unit Requirements by Municipality

Chicago	Chicago Home PageChicago Zoning Administrators OfficeChicago Building Code
Aurora	Aurora Home PageAurora Zoning & Planning DepartmentAurora Zoning Ordinances
Rockford	Rockford Home PageRockford Land Use & Zoning DepartmentRockford Zoning Ordinance
Joliet	Joliet Home PageJoliet Planning & Zoning DepartmentJoliet Zoning Ordinance
Naperville	Naperville Home PageNaperville Planning & Zoning CommissionNaperville Building RegulationsNaperville Zoning Regulations
Springfield	Springfield Home PageSpringfield Office of Planning & Economic DevelopmentSpringfield Building Regulations
Peoria	Peoria Home PagePeoria Planning & Zoning DepartmentPeoria Building RegulationsPeoria Guide to Residential Accessory & Storage Structures
Elgin	Elgin Home PageElgin Planning & Zoning DepartmentElgin Zoning Regulations
Waukegan	Waukegan Home PageWaukegan Planning & Zoning DepartmentWaukegan Building Regulations
Cicero	Cicero Home PageCicero Building DepartmentCicero Building RegulationsCicero Zoning Regulations
Champaign	Champaign Home PageChampaign Building Safety DivisionChampaign Building RegulationsChampaign Zoning Regulations
Bloomington	Bloomington Home PageBloomington Planning & Zoning DepartmentBloomington Building CodeBloomington Zoning Regulations
Decatur	Decatur Home PageDecatur Planning & Development DivisionDecatur Zoning Ordinance
Arlington Heights	Arlington Heights Home PageArlington Heights Building & Life Safety DepartmentArlington Heights Building RegulationsArlington Heights Zoning Regulations
Evanston	Evanston Home PageEvanston Zoning DivisionEvanston Building RegulationsEvanston Zoning Regulatons

Does Chicago Allow ADUs? 

It sure does! Chicago does allow ADUs, including basement or attic conversions and detached coach houses, but only in select areas or under strict conditions. The city rolled out a pilot ADU ordinance focused on specific zoning districts and certain designated neighborhoods.

Recently, the City Council’s Zoning Committee approved expanding ADU rules citywide potentially easing size, parking, and density restrictions and giving homeowners in all 50 wards the opportunity to build units like granny flats or coach houses. If you’re in Chicago, start by: 

1. Checking if your property is in the pilot area and eligible for an ADU via the city’s ADU portal
2. Reviewing conversion and construction standards on the official ADU ordinance page.
3. Staying updated on the potential citywide ordinance changes via the City Council or your alderperson.

Does Aurora, Illinois, Allow ADUs? 

Yes. Aurora’s ADU policy is concise but clear: one detached ADU per single-family home is allowed, and it must be truly secondary to the main house. Detached units are capped at 800 sq ft, with a 20‑foot height limit, while attached ones must remain smaller than the main residence. Additional rules include parking and lot coverage limits for example, front-yard parking limited to 40%, and backyard coverage restrained to 750 sq ft or 25% of the yard, whichever is smaller. To move forward, contact the Aurora Zoning Department and ask what the next step is. 

Does Rockford, Illinois, Allow ADUs? 

Rockford does allow ADUs, but regulations vary by zoning district. You can place an ADU in certain residential zones only with specific setbacks, height restrictions, and additional parking will apply For building permits, the city uses a form for one- and two-family dwellings and accessory structures that aligns with state residential building codes—limits include maximum height and standards for construction documents. To confirm specific ADU size and setback requirements, contact the Planning and Zoning Office or the Construction Services office.

Does Joliet, Illinois Allow ADUs? 

No. In Joliet, the zoning code does not currently recognize ADUs as a permitted accessory use. The city’s official zoning materials list various accessory uses like home-based businesses, but there’s no mention of secondary dwelling units such as granny flats or coach houses. That suggests ADUs are not allowed by right under current regulations.

If you’re thinking of adding an ADU, your best next move is to reach out directly to Joliet’s Community Development or Planning & Zoning Department. Explain what you want to build, a separate home-like unit on your lot, and ask if there is any path forward, such as applying for a variance, special zoning exception, or even requesting a policy update. They’ll guide you to the relevant sections of the code or walk you through any possible application process.

Does Naperville, Illinois Allow ADUs? 

It is not entirely clear at this point. Naperville’s municipal code doesn’t explicitly reference ADUs either, but the city does regulate building permits for accessory structures and residential additions. That implies that while you may be able to build accessory structures, like a shed or garage, using them as independent living units is likely not addressed or allowed under current zoning.

Your next step should be contacting Naperville’s Building Permit Services via their online permitting portal.

Does Springfield, Illinois Allow ADUs? 

Yes it does! Springfield has taken a clear step forward: in February 2025, the City Council approved an ordinance enabling ADUs in certain areas. The rules cap ADU size at half the gross floor area of the main house or 900 sq ft, whichever is smaller, and require the unit to have its own entrance, kitchen, bathroom, and sleeping area. This sets a solid foundation for homeowners looking to add flexible space or secondary units on their property.

To move forward in Springfield, start by reviewing the city’s updated ADU ordinance. Once you’re clear on eligibility, reach out to the City of Springfield Planning & Zoning Department or vice department to verify whether your property is in a permitted area, what permit or site plan review is required, and what documentation to provide before you apply.

Does Peoria, Illinois Allow ADUs? 

Yes, Peoria now formally permits ADUs. The zoning code allows one attached and one detached ADU per single-family lot, with the option for two detached units if the lot is at least one acre and one unit is deed-restricted. ADUs must not exceed 75% of the main house’s floor area or 1,000 sq ft, whichever is less, and must follow standard zoning setbacks, design guidelines, and utility rules. 

Your best next step in Peoria is to access Section 21‑316 of the City Code, which outlines ADU requirements, including appeals if your permit is denied. After you’re familiar with the rules, contact the City of Peoria Planning & Zoning Department, ask which zoning district you’re in, confirm that the ADU is a permitted use, and get started with site plan review or building permit submissions as dictated by the ordinance.

Does Elgin Allow ADUS? 

Elgin’s municipal code doesn’t specifically address ADUs, but it handles permits for accessory structures like sheds, garages, decks, and home improvements elginil.gov+1. That suggests that while accessory structures are generally allowed, regulations on living quarters within them may not be clearly defined.

If you’re considering an ADU in Elgin, your best path is to contact the Elgin Community Development Department or Code Administration Division—ask whether accessory dwellings are permitted or if you’d need a variance or special zoning review. The department can guide you on whether your ADU could qualify under existing accessory structure rules or what additional steps, site plan reviews, or code references you’d need to follow.

Does Waukegan Allow ADUs? 

Yes! Waukegan’s Unified Development Ordinance (UDO) includes a site plan application specifically required for newly constructed ADUs, meaning the city does recognize ADUs in its development process. Although the ordinance isn’t summarized publicly, the formal inclusion of ADUs in site plan procedures confirms they’re part of the regulated landscape under the UDO. 

To move ahead and get specific height and size restrictions,  visit the Planning & Zoning Commission section on the city website to download the Site Plan Approval Application used for ADUs, Then, reach out to the Waukegan Planning & Zoning Department to ask how ADUs are regulated city-wide, confirm what zoning categories allow them, and find out what documentation and approval pathway you need to follow.

Does Cicero Allow ADUs? 

It is uncertain as of now. Cicero doesn’t explicitly recognize ADUs in its municipal code. The zoning ordinance focuses on general structures, occupancy standards, and building safety, but doesn’t provide rules for granny flats, carriage houses, or converted garages. There’s no language allowing or clearly prohibiting ADUs at present. 

Your best next step is to reach out to the Cicero Building & Zoning Department. Explain that you’re exploring an ADU and ask whether the code treats it as an accessory structure, or if you’d need a variance or special review. They’ll guide you on zoning category restrictions and required documentation such as a zoning compliance or conditional use request.

Does Champaign, Illinois, Allow ADUs? 

It looks like they do! Champaign used to prohibit ADUs, but that changed in mid‑2022. The City Council passed Council Bill 2022‑117 to amend the zoning ordinance by adding “Division 9 – Zoning Requirements for Accessory Dwelling Units.” Under this ordinance, you may now build detached, attached, or internal ADUs which are all subject to definitions, placement rules, and eligibility tied to residential zones. The specific requirements will depend on tn

To get started, check the Incremental Development section on the City’s Planning & Zoning page to view the ADU package and resources. Then contact the City of Champaign Planning & Zoning Department to confirm which zoning districts allow ADUs, what size or design standards apply, and how to begin permit submissions.

Does Bloomington, Illinois, Allow ADUs?

It sure does! Bloomington now explicitly allows ADUs per local code that was updated in February 2023 to clearly define and regulate them. Key details of the code include mandated owner occupancy  and a maximum size of 800 sq feet (or 50% of the main house). The ADU must be located behind the primary dwelling and have its own parking space, plus maintain architectural consistency with the main house.

To move forward, check out Bloomington’s development services site to access zoning maps, code text, and permit forms. Then reach out to the Bloomington Planning & Zoning Division to confirm your property’s zoning designation, learn what reviews or applications are needed, and get a permit rolling.

Does Decatur, Illinois, Allow ADUS? 

Unfortunately, Decatur doesn’t currently have a clear, publicly accessible policy or zoning language allowing accessory dwelling units specifically. The city’s building code focuses on general requirements like permits, plan review fees, and removal of accessory structures when the main home is removed, but doesn’t define whether secondary living units are permitted or not. 

To figure out your path forward, the best approach is to contact the City of Decatur’s Planning & Zoning Department. Ask whether ADUs are allowed under current zoning regulations or if zoning amendments, conditional uses, or variances are required.

Does Arlington Heights, Illinois, Allow ADUs? 

It is uncertain. Arlington Heights does not explicitly accommodate ADUs in its zoning code. The village permits various accessory buildings only in rear yards, with strict limits on size, height, and floor area ratio. None of these allowances cover living spaces like ADUs. 

If you’re exploring the possibility of adding an ADU, your next step should be to contact the Village’s Planning & Community Development Department (or Building & Life Safety). Inquire about whether ADUs could be considered under existing accessory structure provisions or through a variance or special zoning application. 

Does Evanston, Illinois, Allow ADUs? 

Yes! Evanston is one of the more progressive Illinois cities when it comes to ADUs. Since a 2020 amendment, attached/internal ADUs and detached coach-house style units have been permitted across most residential zones. The city also offers an Evanston Guide to Accessory Dwelling Units, a homeowner-friendly tool outlining zoning, building, utility, and design requirements. Some of the basic requirements include a maximum size of 1,000 square feet (for detached units) and only one ADU per lot. To get started in Evanston:

• First, download and review the ADU Guidebook, accessible through the city’s Community Development page.
• Use the “About My Place” tool on the city’s zoning website to identify your property’s zoning district and related ADU rules.
• Then, reach out to the Evanston Zoning Department with your property details to confirm district-specific allowances, steps for permit review, and how to register an ADU for rental use if applicable. 

Looking for an ADU Builder Serving Illinois? 

We know it can be difficult finding an ADU builder with transparent processes and pricing you can trust. Psy Homes is pleased to offer you our years of experience and knowledge to make your ADU vision become reality. Our ADU package includes a customized design experience, a completed luxury modular ADU, and delivery and setup right where you want it. Contact us today or browse our models to find the best one for your needs. You can also easily request a free quote to get the process started!