To check if your apartment is legal to rent, compare the unit you’re living in (or looking at) against two public records: the property’s Certificate of Occupancy, which says what the building is approved for and how many dwelling units it may contain, and the zoning designation for the lot, which says what uses the land itself allows. If the apartment matches both, it’s legal. If it doesn’t, the gap is your answer.
The check has three parts: a walk-through of the unit for physical red flags, a records pull from the local building department, and a zoning lookup. None of them takes long once you know what to ask for.
Walk Through the Unit First
Before you touch any records, the space itself will often tell you whether it was designed and approved as a dwelling. No single item below proves an apartment is illegal, but two or three together are a strong signal to keep digging.
- No second way out. A legal bedroom needs an emergency escape opening, typically a window large enough to climb through. The widely adopted International Residential Code sets the minimum at 5.7 square feet of clear opening with a sill no higher than 44 inches from the floor. A bedroom with no window, or only a tiny fixed pane, almost certainly wasn’t approved for sleeping.
- Low ceilings. Building codes generally require a minimum ceiling height of 7 feet in habitable rooms. Basement and attic conversions frequently fall short, and it’s one of the easiest things to check yourself with a tape measure.
- No windows in living spaces. Bedrooms and living areas need natural light and ventilation. A room with no operable window was likely never designed as living space.
- Improvised kitchen or bathroom. A shower head rigged over a utility sink, a hot plate where a stove should be, or a bathroom carved out of a closet all suggest a retrofit without permits.
- Electrical problems. Extension cords doing the job of permanent wiring, exposed junction boxes, or a breaker panel that looks self-installed all point to work that was never inspected.
- Shared utility meter. If multiple apartments share one electric or gas meter, the building may have been carved up without updating the utility infrastructure. Large complexes sometimes use master metering legitimately, but in a small building with separately rented units, a single meter is a red flag.
- Cash-only rent and no written lease. A landlord who insists on cash and refuses to put anything in writing may be avoiding a paper trail on the unit itself.
Certain spaces get converted into unpermitted rentals far more often than others. Basements top the list because the space and utilities are already there, but they routinely fail on ceiling height, egress windows, and moisture control. Attics have the same problems plus limited exits and rarely a second stairway. Garages lack the insulation, plumbing, and electrical capacity a dwelling requires. Subdivided apartments are harder to spot because they look like real apartments; the tells are windowless rooms, hallways that don’t make architectural sense, and bedrooms only reachable through other bedrooms.
Get the Certificate of Occupancy
The Certificate of Occupancy is the document that settles the question. A local building department issues it after a property passes required inspections, and it confirms two things: what the building can legally be used for, and how many dwelling units it’s approved to contain. A building with a Certificate of Occupancy listing it as a single-family residence cannot legally contain three apartments, however nicely they’re finished.
The certificate typically lists the property address, the approved use classification (residential, commercial, mixed-use), the number of permitted dwelling units, the number of stories, and the date it was issued. Some jurisdictions issue a Certificate of Compliance that serves the same function. What you want is the official document that says the property is approved for a specific number of residential units. If your apartment would be unit four in a building approved for three, that’s your answer.
One detail people miss: a Certificate of Occupancy reflects the building’s status at the time of its last inspection and approval. If a landlord later subdivided a unit or converted a basement without permits, the existing certificate won’t mention it. The certificate tells you what’s legal. The gap between the certificate and the reality of the building tells you what isn’t.
Ask the Landlord
Start with the most direct approach: ask the landlord or property manager for a copy of the Certificate of Occupancy. A landlord with nothing to hide should produce it without fuss. Deflection, a claim they don’t have it, or a “no one’s ever asked me that” doesn’t prove the unit is illegal, but it means you verify on your own.
Search Municipal Records Online
Most cities and counties maintain online portals through their building department, code enforcement office, or planning department where you can search property records by address. Department names vary, but searching “[your city] building department property search” or “[your city] certificate of occupancy lookup” will usually get you to the right place. These databases let you pull up a property’s Certificate of Occupancy, permit history, inspection records, and any open code violations.
Permit history is especially useful. If records show permits for a kitchen installation or bathroom addition in the basement, that’s a good sign the conversion was done properly. No permit history at all for what’s obviously a converted space is a strong indication the work was never approved.
Visit the Building Department
When online records don’t cover the property or the system is hard to navigate, go in person. Staff can pull the property file and walk you through what’s on record. Some jurisdictions require a formal public records request, sometimes called a Freedom of Information request, which may take a few days. In many offices a staff member can look up basic information on the spot.
Contact Code Enforcement
If you’re already in a unit you suspect is illegal, your local code enforcement office or housing authority can look up the property’s violation history and legal status. You can also file a complaint requesting an inspection. Be aware this can result in the unit being officially declared uninhabitable, which triggers its own consequences discussed below.
Check the Zoning Separately
The Certificate of Occupancy tells you what the building is approved for. Zoning tells you what the land itself is allowed to be used for. These are related but separate checks.
Every parcel of land in an incorporated area has a zoning designation. Residential zones are typically labeled with codes like R-1 (single-family), R-2 (two-family), or R-3 and above (multi-family). The specific codes and what they permit vary by jurisdiction, but the principle is consistent: the designation caps the number and type of dwelling units allowed on the lot.
You can usually find a property’s zoning through your city’s planning department website, which often includes an interactive zoning map. Look up the address, note the code, and check the local zoning ordinance for what that code permits. If the property is zoned R-1 but contains two separate apartments, the second unit violates the zoning unless a variance or special permit was granted.
Accessory dwelling unit laws matter here. At least 18 states have passed laws broadly allowing homeowners to build and rent ADUs on single-family lots. In those states, a detached garage converted into a studio may be perfectly legal if it was permitted under the ADU rules. The difference between a legal ADU and an illegal conversion is still permits, inspections, and a paper trail.
Why the Check Matters
Illegal apartments skip the inspections designed to catch fire hazards, structural problems, and electrical defects. That’s the safety piece. The legal piece is that in many jurisdictions a lease for an illegal apartment is unenforceable, which cuts both ways: the landlord may not be able to collect unpaid rent in court, but the lease may not protect you the way you expect either. Courts in some areas have allowed tenants to recover rent already paid to a landlord who knowingly rented an illegal unit; other jurisdictions limit that remedy based on whether the tenant knew.
Displacement is the most immediate risk. If code enforcement determines the unit is uninhabitable, they can issue a vacate order requiring you to leave, sometimes with very little notice. The landlord may face fines of hundreds to thousands of dollars per violation, potentially assessed daily, but those fines don’t put a roof over your head. Some jurisdictions require landlords to pay relocation assistance to displaced tenants who didn’t know the unit was illegal; that protection is not universal, and enforcing it can require legal action.
Renter’s insurance policies generally require the insured premises to be a legal dwelling. If you file a claim and the insurer discovers the unit was never approved for residential occupancy, the claim can be denied. Landlord insurance faces the same problem, which means an injury caused by a hazardous condition in an illegal unit may leave no insurance on either side to cover it.
If Your Apartment Turns Out to Be Illegal
Document everything first. Photograph the unit’s condition, save all communications with the landlord, keep copies of rent payments, and preserve your lease if you have one. This documentation protects you no matter what happens next.
Contact your local housing authority or a tenant rights organization to understand your specific protections. In most places a landlord cannot legally evict you in retaliation for reporting an illegal unit, though the unit itself may still be ordered vacated by the building department. The landlord isn’t throwing you out; the government is declaring the space unfit.
Depending on your jurisdiction, you may be entitled to withhold rent, recover rent already paid, or receive relocation assistance. Consulting a tenant’s rights attorney, many of whom offer free initial consultations, is worth the time. The landlord’s exposure to fines, license revocation, and potential criminal liability for serious safety violations gives you meaningful leverage in negotiating a resolution, whether that’s relocation costs, lease termination, or the landlord actually bringing the unit up to code.
The worst move is doing nothing. An illegal apartment doesn’t become safer because you’ve gotten used to it, and the building department doesn’t forget about violations because time passes.