How to Legalize a Basement Apartment in New Jersey
Garden State ADU finishes basements, builds basement suites, and helps New Jersey homeowners bring an existing second unit into compliance: a basement apartment, a finished attic with a kitchen, a garage someone has been living in.
- First questionFirst question
- Your zoneYour zone
- Second questionSecond question
- PermitsPermits
- FallbackFallback
- One dwellingOne dwelling again
Basements finished, suites built, units brought up to code.
A basement is square footage you already own. Finishing it for your own household is a construction-permit job. Turning it into a place where someone else lives, with its own entrance and kitchen, is a zoning question first.
We do not quote dimensions here, because the construction official applies the code to your building, not to a general case. We look at those items on site before you file, so you know what the work is.
What decides most basement units
- How someone sleeping there gets out in an emergency
- Ceiling height
- The separation between the two units
- Smoke and carbon monoxide alarms
Three kinds of basement job
A finished basement
More living space for your own household, built under permit. In an existing house the Rehabilitation Subcode is the starting point, and finishing a basement for habitable use does not by itself require raising the ceiling to the height required in new construction.
A basement suite for family
A bedroom, bath and living space that stays part of one residence, like an in-law suite. Your town's definition of a second kitchen decides how far it can go.
Legalizing an existing unit
An apartment that is already there, brought into compliance. Which route that takes depends on your zone, and it is the rest of this page.
Who calls us about a basement.
You bought a house with an apartment in it
Set up by a previous owner, with no paperwork you can find. The first question is whether your zone allows it at all.
Family has been living downstairs
A unit set up for a family member years ago. If the person living there is family and you are not charging rent, a family-suite provision may be the category it belongs in.
You want to finish the basement
More room for your own household, built under permit from the start.
First: does your zone allow a second unit at all?
Everything else follows from this. In New Jersey each municipality writes its own zoning, so the answer is in your town's ordinance and in the zone your lot sits in. There are three possibilities.
Your zone permits it. Some zones allow two-family houses. Some towns permit an accessory apartment or an accessory dwelling unit under conditions. If your unit fits what the ordinance allows, the problem is paperwork and construction, not zoning. Our town-by-town guide lists the towns we have verified.
Your town permits a family-only suite. A number of New Jersey towns have a mother-daughter provision. If the person living in the unit is family and you are not charging rent, that may be the category your unit belongs in, with its own conditions.
Your zone permits neither. This is a common case. It does not end the conversation, but it changes the routes available, which are the next section.
Three routes.
1. A use variance
The zoning board of adjustment can permit a use in a district that is restricted against it. State law sets the bar: the board may do it in particular cases for special reasons, and only where it can be granted without substantial detriment to the public good and without substantially impairing the zone plan. It is a hearing, and the outcome is the board's decision. Some owners win these. It is not the route to count on.
2. Showing the unit predates the rule
The Municipal Land Use Law says a nonconforming use existing at the time an ordinance is passed may be continued. It also lets an owner apply for a certification that the use existed before the ordinance made it nonconforming, from the town's administrative officer within a year of the ordinance's adoption, or from the board of adjustment at any time. If your house has been a two-family since before your town's zoning said otherwise, and you can show it with tax records, old permits or similar documents, this is the route to look at.
Some towns publish a process for exactly this kind of question. Woodbridge Township lists an application titled "Legalize a Two-Family or Multi-Family Dwelling" on its Planning and Zoning forms page, alongside its variance application. Check your own town's forms page for something similar before assuming there is no path.
3. Going back to one dwelling
Many New Jersey towns treat a second kitchen as the thing that makes a second dwelling unit. Removing the range and its hookups, and opening the unit back up to the rest of the house, can turn an illegal apartment into a finished basement or an in-law suite that is part of one residence. You give up the separate apartment and keep the finished space, legally.
Second: permits and inspections.
Once the zoning question has an answer, the construction side begins. New Jersey's Uniform Construction Code makes it unlawful to alter a structure, or change the use of part of one, without a construction permit, and it requires a certificate of occupancy before a changed use begins. Legalizing work that was done without permits means applying for them now. In practice that means drawings of what exists, permit applications to your local construction office, and inspections of work that is already covered up. Expect the inspectors to ask for some finished surfaces to be opened so they can see wiring, plumbing and framing.
For an existing house the state's Rehabilitation Subcode is the starting point. The Department of Community Affairs describes it as the place where every project in an existing building begins, because it sets out which parts of the code for new construction apply. One useful example from the Department: finishing an existing basement for habitable use does not, by itself, require raising the ceiling to the height required in new construction.
A separate apartment raises more questions than a finished basement does. The ones that decide most basement units are how someone sleeping there gets out in an emergency, ceiling height, the separation between the two units, and smoke and carbon monoxide alarms.
If the unit will be rented, there is one more state rule to know. Before a one- or two-family home is sold, leased or otherwise changes occupancy, the owner has to obtain a certificate of smoke alarm, carbon monoxide alarm and portable fire extinguisher compliance from the local enforcing agency. Some towns, Woodbridge among them, also publish their own rental inspection form.
What it costs.
Your written estimate gives the real number.
Legalizing a unit depends on what is behind the finished walls and what your town requires, and nobody can price that from a photo. We look at the space, tell you what the construction side is likely to involve, and give you a written estimate. The site visit and estimate are free.
Building a basement suite for family? Our in-law suite page lists New Jersey market ranges for that.
How the job runs.
Start with the free zoning check. Tell us what exists on the property now. We read your municipality's rules without contacting the town to see which route you are likely on, and Osama reaches out to you personally, by phone or text.
In Central Jersey we can then look at the unit, tell you what the construction side is likely to involve, prepare the permit applications, and do the work to bring it up to code or to return the house to a single dwelling. Elsewhere in New Jersey we can connect you with a builder in your area. Where a variance is involved, the Design & Permit agreement comes first.
- 01Call or send the formFREE
- 02We check your zoningFREE
- 03Site visit and written estimateFREE
- 04Design
- 05Approvals and permits
- 06The build
- 07Final inspection
Straight to a build contract
These go from the written estimate straight to a construction contract.
Questions about legalizing a second unit in New Jersey.
Can an illegal basement apartment be made legal in New Jersey?
Sometimes. It turns on whether your zone allows a second dwelling unit on your lot. If it does, the route is construction permits, inspections and a certificate of occupancy. If it does not, the routes are a use variance from the zoning board, proof that the unit lawfully existed before the zoning changed, or removing the second kitchen so the house is a single-family home again.
What if the apartment was there when I bought the house?
That can matter. New Jersey's Municipal Land Use Law lets a nonconforming use that existed when an ordinance was passed continue, and it lets an owner apply for a certification that the use existed before the ordinance made it nonconforming. You would need to show it, usually with old records. A unit that was simply never permitted is a different case.
Do I need permits for work that is already finished?
Yes. The state's construction code makes it unlawful to alter a structure, or change the use of part of one, without a permit. Legalizing a unit means applying for the permits now and letting the inspectors see the work, which can include opening finished surfaces.
Does the basement ceiling have to be seven feet high?
Not necessarily in an existing house. New Jersey's Department of Community Affairs has written that work in an existing building starts with the state's Rehabilitation Subcode, and that finishing an existing basement for habitable use does not by itself require raising the ceiling to the height required in new construction. How that applies to a separate apartment is for your local construction official to decide.
Will asking the town about it get me in trouble?
We are contractors, not lawyers, and we cannot promise how a town will respond. What we can do is read your zoning first without contacting the town, so you know which route you are on before you file anything. If the facts are complicated, a land use attorney is worth the consultation.
Find out which route you are on.
The estimate is free and so is the site visit. We read the rules without contacting your town.
- 01Osama reaches out to you personally, by phone or text.
- 02We check your town's zoning for your address.
- 03We walk the property and measure.
- 04You get a written estimate. No obligation.