Can Chicago Order You to Remove an Illegal Conversion?

By Katarina Karac, Founding Attorney, Birchwood Law | Last reviewed October 2026

Yes. When a dwelling unit or new use is added to a Chicago building without the required permits, certificate of occupancy, and zoning approval, the city can require the owner to bring the property into compliance. When the space cannot be legalized, compliance means restoring the building to its approved layout, a process commonly called deconversion.

The citywide Additional Dwelling Unit (ADU) ordinance passed in September 2025, effective April 1, 2026, created a legal path for many basement and attic units. It did not legalize units that already exist without permits.

This article explains the legal basis for removal orders, how enforcement typically begins, when legalization is realistic, and what investors should check before acquiring a building with a suspected illegal unit.

What Chicago Treats as an Illegal Conversion

An illegal conversion is a change in the number of units, or in the use or occupancy of a building, made without the approvals that change requires.

Typical examples include:

• A basement, attic, or garden apartment added without permits.
• One dwelling unit divided into two.
• A storefront converted to a residence.
• Warehouse or industrial space converted to offices, an event venue, or living space.

DOAH’s Buildings Hearings Division lists illegal construction and conversions without proper permits among the zoning violations it adjudicates.

The Legal Basis for a Removal Order

An illegal conversion usually violates three bodies of rules at once.

1. Zoning. The added unit or new use may exceed what the district allows under the Chicago Zoning Ordinance (Title 17).
2. The construction codes. A change of occupancy is prohibited until the building official issues a certificate of occupancy (Section 14A-7-702.3). The converted space must also meet egress, fire separation, and habitability standards it was never reviewed against.
3. Continuing offenses. Each violation, and each day it continues, is a separate offense under the Section 14A-12-1203 fine tables.

Enforcement authority follows from those violations. A DOAH administrative law officer may issue orders consistent with the Municipal Code (Section 2-14-076). The construction codes also authorize the city, through the Corporation Counsel, to seek an injunction requiring compliance (Title 14A). Where the unit cannot meet zoning and code requirements, the only compliant outcome is removal.

Neighborhood Housing Services of Chicago frames the owner’s choice the same way in its guide to basement units: bring the unit into compliance, or deconvert it under permit.

The remedy defense in Section 2-14-155(b) matters here. A violation remedied by the hearing date is a defense to liability for many building code provisions. Each day an illegal unit remains occupied after citation is another day of potential fines.

What Happens When a Chicago Inspector Finds Unpermitted Work

The Department of Buildings’ published enforcement process describes what follows in Chicago:

1. Complaint triage. Bureau supervisors review 311 complaints at the start of each business day and prioritize those needing immediate inspection. Unpermitted units also surface during inspections for unrelated permitted work.
2. Inspection. Inspectors verify the complaint and check smoke and carbon monoxide detectors and means of egress, including interior and exterior stairs and porches. If an owner or tenant refuses entry, the Department must obtain a court order to inspect the interior.
3. Enforcement level. A supervisor assigns the violations to a track. Non-hazardous life-safety items go to DOAH, and dangerous or hazardous conditions go to circuit court. An illegal unit with blocked or missing egress is a likely circuit court candidate.
4. Stop work orders. If construction is still underway, the city may issue a stop work order. Removing a posted order without authorization is itself a violation.
5. Hearings. Cases are typically continued while the owner pursues either legalization or deconversion under permit.

Either path requires permits. Removing a unit without a permit can produce new violations. For the hearing process itself, see how code violation hearings work in Illinois.

When an Existing Unit Can Be Legalized Under the ADU Ordinance

The citywide ADU ordinance distinguishes conversion units, which sit inside the existing building (typically a basement or attic), from detached coach houses. The city’s announcement confirms both types are now permitted. Conversion units can be established without a zoning change in districts zoned for multi-unit buildings and in certain business and commercial districts.

Several conditions shape whether an existing illegal unit can take that path:

• Single-family (RS) districts carry added restrictions, including owner occupancy, and individual alderpersons control whether their wards opt in.
• Affordability requirements carried over from the pilot program.
• Short-term rentals are prohibited in ADUs.
• Building code compliance still applies. Legalization requires permits, plans, and code compliance for egress, fire safety, ceiling height, light, and ventilation.

For many existing basement units, those standards require construction, not just paperwork. Birchwood’s analysis of the ordinance is in Chicago Legalizes Citywide ADUs, But with Major Caveats for Property Owners.

If the unit does not qualify as an ADU, other zoning routes may apply depending on the lot and district. These include a variation, an administrative adjustment, or a map amendment.

It’s important to consider the total cost of legalizing a basement unit, including the building requirements for egress and ceiling height. The costs are a critical factor, and a big factor that sets apart projects that move forward from ones that do not.

Why Long-Standing Units Are Not “Grandfathered”

Legal nonconforming status protects uses and structures that were lawfully established before the rules changed. A unit that was never permitted was never lawfully established, and its age does not change that. The distinction is covered in more depth in Birchwood’s guides to non-conforming structures and uses and renovating a grandfathered property.

Commercial Changes of Occupancy

The same principles apply to commercial space, at higher stakes. The city requires a certificate of occupancy for:

• Any change of occupancy, such as converting a warehouse to offices.
• Substantial alteration of more than 10,000 square feet of non-residential space.
• Assembly, educational, institutional, or hazardous occupancies regardless of size. Assembly use means a space where more than 50 people gather.

A tenant that opens an event space, fitness studio, or school in a building never approved for that occupancy exposes both itself and the owner to enforcement.

Due Diligence Before Acquiring a Building With a Suspected Illegal Unit

• Compare the actual unit count and uses against the permit and inspection history in the city’s building records search.
• Check open and past violations on the Chicago Data Portal.
• Get written representations from the seller about unpermitted work, and allocate responsibility for legalization or deconversion in the purchase contract.
• Obtain a zoning analysis before closing if the underwriting depends on income from a unit that may not be legal.

Challenging a Removal Order

An owner who believes a DOAH order requires more than the code demands can seek administrative review in circuit court. The complaint must be filed, and summons issued, within 35 days of service of the decision. See how to appeal a code violation decision in Illinois.

Counsel for Illegal Conversion Violations

Birchwood Law advises owners and investors facing illegal conversion citations in Chicago and across Cook, Lake, and DuPage Counties. That work includes evaluating whether legalization is realistic before money is spent on construction or deconversion. See our land use and zoning services, or contact Birchwood Law to review a specific property.

This article provides general information about Illinois law and is not legal advice. Reading it does not create an attorney-client relationship.