How To Combine Apartments In NYC

by | Last updated Jun 11, 2024 | Apartment Renovations, Renovations

To combine two apartments into one in NYC, you will need to hire an architect to design the apartment combination and file for permits with the NYC Department of Buildings. In most cases, the architect will file an Alteration Type 2 application with the NYC DOB as per TPPN #3/97. 

You can combine two adjacent apartments to make one apartment in NYC without obtaining a new Certificate Of Occupancy, as long as you follow the regulations of TPPN # 3/97 DOB Policy. The DOB regulations of TPPN #3/97 outline the requirements for an apartment combination in NYC under an Alteration GC formerly known as an Alt 2 application. Apartment combinations that do not comply with TPPN #3/97 must obtain a new Certificate of Occupancy and be filed as an Alt CO, formerly known as an Alteration Type 1. Getting a new Certificate of Occupancy would be a lengthier and more complicated process. If the apartments are Condos, the combination must also be filed with the Department of Finance.

I am Jorge Fontan, an architect in NYC and owner of Manhattan-based architecture firm Fontan Architecture. I have worked on many loft and apartment combinations in NYC. In this post, I will review some of the things you should know before beginning the process of combining apartments in NYC.


Combining Apartments

Combining apartments is quite common in New York. This trend has become very popular because it is often easier to buy a neighbor’s apartment when they move than to find a larger apartment. Combining two apartments into one may be the most convenient way to double your apartment size.

You will need to hire an architect when combining apartments, and you’ll need to acquire permits from the NYC Department of Buildings. You also want to ensure the design works well. The apartment layout should not have a thrown-together feel. The apartment should flow properly, suit your needs, and fit your aesthetic sensibilities. It is never too early to talk to an architect. People constantly call me before they purchase their apartments. On many occasions, we have begun working on the design before closing.

You will need approval from your Condo or Co-Op Board before beginning the renovation. Don’t be overwhelmed, as an architect, we handle most of this for you. It is good for you to review your Building’s Alteration Agreement before renovating. The agreement is between you and the building with regard to your renovation. You can check out an article we wrote on Alteration Agreements to learn more about the process

Combining two apartments NYC

Combining two apartments NYC


Where to Start Your Combination

When combining two apartments into one (or combining multiple apartments), the first step is to discuss it with an architect. An architect, such as myself, can help you understand any possible issues and the logistics involved as well as discuss design and project budgets.

You or your architect can contact the board or building management company to discuss your apartment combination. Although most buildings will not object, there may be some that do. You will need to hire an architect to file the job with the NYC Department of Buildings and assess the existing conditions and plan how to combine the units.


Combining Two Apartments Before and After

One of the most important things I can say about combining apartments is that you want the apartment to feel like it was one apartment from the start. A cohesive design is much easier to achieve if you do a total gut renovation.

In the before and after photo below, we have a project where we combined two apartments into one and fully gut renovated. The owner initially told me he wanted to connect the two apartments with a doorway. I suggested we knock down the wall between the two living rooms to create a more open space. By removing the walls, we made a family room on one side, an open kitchen in the middle, and a living room on the other. These rooms are now all interconnected and open.

NYC Apartment Combination Before & After

NYC Apartment Combination Before & After


The design and planning of an apartment combination is critical to how the final product will feel. As an architect, I always start by assessing the existing conditions and figuring out how to optimize the space for use and bring a design that balances aesthetics and function. Below is another view from the same apartment, showing how opening the rooms makes it feel larger and more connected.

Combining two apartments into one before and after


Approvals and Permits for Combining Apartments in NYC

Since the Certificate of Occupancy of a building lists the number of apartments, one would assume that combining apartments requires a new Certificate of Occupancy and, therefore, an Alt CO or Alt 1 filing. This is not always the case. The following are the requirements and regulations for combining apartments without changing the Certificate of Occupancy and filing only as an Alteration or Alt 2. This protocol is based on information in the NYC DOB Technical Policy and Procedure Notice #3/97, also known as TPPN #3/97. These are the rules for combining apartments in NYC without getting a new Certificate Of Occupancy.

DOB rules for combining apartments in NYC without a new Certificate Of Occupancy:

  • The architect must file an Alteration GC or Alt Type 2 with NYC DOB
  • The apartment must be adjacent or connected vertically on only two floors
  • You cannot change the means of egress
  • New rooms must comply with light and air regulations
  • You must end up with only one kitchen
  • For Condos, you must file with DOF for a new tax lot


Renovating and Combing Apartments NYC

Renovating and Combing Apartments NYC


For Condos ONLY

If we combine apartments in a condominium building, you must obtain a new Tentative Tax Lot number from The Department of Finance (DOF) before filing with DOB. To file with the Department of Finance for this work, we will submit architectural plans and an application for Amending the Condominium Apportionment. If your building has an attorney who handles your Condominium documents, you should speak with them and get a preliminary consultation. If you are in a Co-Op, you can skip this step.


DOB Approvals and Permits 

The following items are for both Co-Ops and Condominiums. You can see another post we have on How to Renovate Your Co-Op Apartment in NYC if you would like to learn more. 

Type of Apartment Combinations Allowed as an Alt 2:

Combined apartments are on the same floor. Example: If you are connecting two apartments into one that are side by side, this will not require a new C of O. If you are doing a vertical combination adding interior stairs in the apartments, you can only combine apartments two stories in this application type. If this is three stories, you will need to file for a new C of O.

Code Requirements

Light And Air:

  • All new rooms must comply with the building code requirements for windows to achieve natural light and air.
  • Any existing rooms that have windows but do not have sufficient light and air requirements are “grandfathered.” They must not have the current amount of windows reduced.


  • You cannot change any of the means of egress when you combine apartments, including, but not limited to:
    • Fire escapes
    • Building stairs
    • Lobby
    • Building corridors


  • You can only have one kitchen when you combine apartments.
  • If the original kitchens are next to each other and combined, any removed plumbing and gas fixtures must be capped.
  • If the kitchens are separate, one of them must be completely removed and all plumbing and gas must be capped (unless you are replacing with another use, such as a new bathroom or wet bar).

DOB Filing:

  • When combining apartments in NYC, a licensed architect or engineer will file the job with DOB. The Department of Buildings plan examiner must review and approve the plans and documentation.


  • For Sign-off of the work, you will request a letter of completion from the Department Of Buildings.


Turning One Kitchen into a Bathroom 

We always want to consider reusing the second kitchen’s plumbing since you already have plumbing there. This can be an excellent opportunity to make a wet bar for the living room or add a bathroom if it better suits your needs. If it does not, we can cap off the plumbing and gas and bury the piping in the wall. The picture below shows a bathroom we built in place of a kitchen we removed in an Upper East Side apartment combination.

Turning kitchen to bath when combining apartments

Turning kitchen to bath when combining apartments


Assessing Walls for Demolition

If you combine apartments, you will need to demolish some walls or at least open a door in a wall. We first have to assess to determine if the wall is load-bearing or not. We also want to determine if there are utilities in that location. For example, sometimes, we find gas pipes in strange places during construction.

If the wall is a load-bearing or masonry wall, we can still open it, but this will be more complicated and certainly increase the budget. Only an architect or structural engineer should determine whether a wall is load-bearing.


If You are Planning on Combining Apartments in NYC, You Will Need an Architect

Combining two apartments into one may feel like a big job, but it can be a relatively painless process with proper planning and a good team. Renovations can be stressful and time-consuming, but deal with one issue at a time, and you will get through it just fine. Make sure to hire a good team that you feel comfortable with and can trust.


Apartment Combination Cost

So, how much does it cost to combine two apartments in NYC? That is going to depend on many factors. The most significant cost by far is the construction. The cost of combining apartments will depend on the extent of the renovation. If this is going to be a gut renovation, the price will be much higher. Heating and air conditioning, for example, could be a significant cost if you are re-configuring rooms. The level of quality will also affect the price. The price will increase if you work with high-end products and finishes.




Combining two apartments into one apartment

Brooklyn Apartment Combination & Renovation

In this example, we joined two condo apartments in Brooklyn Heights with a complete gut renovation.

Combining Two Apartment into One NYC

Combining Two Apartment into One NYC


Combining Two Lofts in SoHo

This project combines two duplex lofts in SoHo to make one combined 6,500-square-foot loft. This is a high-end apartment renovation and gut renovation.

Combining Two Loft Apartments in NYC

Combining Two Loft Apartments in NYC


Combining Apartments

If you plan to combine apartments, the first step is to consult an architect. Make sure you are working with highly qualified professionals for design and construction. I study design and construction as an architect, but these are complicated and quite involved issues. Every project is different and must be assessed based on its unique characteristics. This post does not assume to cover every possible issue or condition but rather to provide a general overview of the topic.


Thank You for Reading our blog post on combining apartments in NYC.

I hope this was helpful. If you want to speak with an architect about a potential project, you can contact us at Fontan Architecture directly. If you are looking for an architect to work on an apartment combination or other type of project, please see our Combining Apartments Architectural Services.


Contact Fontan Architecture


External Sources: NYC DOB TPPN #3/97 DOB Code Notes Combining Apartments

Jorge Fontan

Jorge Fontan

This post was written by Jorge Fontan AIA a Registered Architect and owner of New York City architecture firm Fontan Architecture. Jorge Fontan has earned 3 degrees in the study of architecture including two degrees from the City University of New York and a Masters Degree in Advanced Architectural Design from Columbia University. Jorge has a background in construction and has been practicing architecture for 20 years where he has designed renovations and new developments of various building types.