How To Combine Apartments In NYC

by | Last updated Apr 18, 2022 | Apartment Renovations, Renovations

In order 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 in accordance with TPPN # 3/97 on the NYC DOB. Two adjacent apartments can be combined 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 outlines the requirements for an apartment combination in NYC under an Alt 2 application. Alternatively, apartment combinations can be filed as an Alteration Type 1, although this would be a lengthier and more complicated process.

I am an architect in NYC and owner of Manhattan based architecture firm Fontan Architecture. I have worked on many apartment and loft combinations in NYC. If you are looking to combine apartments, below we will review some of the things you should know before beginning the process.


Combining Apartments

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

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

Before doing any work in your apartment you will need to review your building’s alteration agreement. To learn more you can check out an article we wrote on Alteration Agreements


Apartment Combinations

The first step when combining two apartments into one (or combining multiple apartments) is to contact your board or building management company. You will need to find out if they allow this practice. 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, more importantly, to assess the existing conditions and plan out how to combine the units.

I find the biggest point of confusion for my clients on these types of projects is the protocol. When do you need to update your certificate of occupancy? Do you file an Alt 1 or an Alt 2? Here is some quick background information before we dive in.

  • Certificate of Occupancy (“C of O” or “C.O.”)  is a document issued by the Department Of Buildings (DOB) that lists the approved occupancy of a building, including the number of floors, the uses per floor, and, when relevant, the allowable number of occupants. A certificate of occupancy in a residential building, for example, would list how many apartments there are per floor. We have another post if you want to read more about what a Certificate of Occupancy is.
  • An Alteration Type 1 (Alt 1) is an application to the Department Of Buildings (DOB) in which the work to be performed in the alteration would require a new updated Certificate Of Occupancy.
  • An Alteration Type 2 (Alt 2) is an application to the Department Of Buildings (DOB) in which the work to be performed in the alteration would not require a new updated Certificate Of Occupancy.


Coordinate With Building Management and Board

In most cases your building will not want you to file an Alt 1. The Certificate of Occupancy is for an entire building, so we always try to make this work as an Alt 2 and avoid touching the C of O. Additionally, filing an Alt 1 takes longer than an Alt 2 and has more requirements. The best practice is to leave the Certificate of Occupancy alone if possible.


Combining Apartments in NYC

Since the Certificate of Occupancy of a building lists the number of apartments in the building, one would assume that combining apartments requires a new Certificate of Occupancy and therefor 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 Alt 2.

This article is based on information in the NYC DOB Technical Policy and Procedure Notice #3/97, TPPN#3/97. These are the rules for combining apartments in NYC for an “Alt 2.”

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

  • Architect must file an Alteration Type 2 with NYC DOB
  • Apartment must be adjacent or connected vertically on only 2 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 new tax lot


Renovating and Combing Apartments in NYC

Apartment Combination of two apartments we combined and gut renovated in a Brooklyn Condo Building

For Condos ONLY

If the work to be performed is in a condominium building, you must obtain a new Tentative Tax Lot number from The Department Of Finance (DOF) before filing the Alt 2 with DOB. To file with the Department of Finance for this type of work you will need to submit architectural plans and an application for Amending 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.


Permits for Combining Two Apartments Into One in NYC

The following items are for both Co-Ops and Condominiums.

Type of Apartment Combinations Allowed as an Alt 2:

Combined apartments are on the same floor. Example: If you are combining two apartments into one that are side by side, this will not require a new C of O.

If the apartments are on adjacent floors and you are doing a vertical combination with an interior stair in the apartments, you can only combine apartments on two floors maximum in this application type. If this is a triplex you will need to file an Alt 1.

Code Requirements

Light And Air:

  • All new rooms created 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.

Sign off:

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


Turning One Kitchen into a Bathroom When Combining

We always want to at least consider the option of reusing the second kitchen’s plumbing, since you have plumbing already there. This can be a great opportunity to make a wet bar for the living room, or add a bathroom if it better suits your needs. If it does not, then we can cap off the plumbing and gas and bury the piping in the wall.

The picture below is of 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 are going to 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 this wall is load bearing or not. We also want to try to figure out if there are utilities in that location. 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 be making the determination if a wall is load-bearing or not.

The picture below is of an Upper West Side apartment combination finished. In this apartment, there is a 12 inch thick brick bearing wall between the two apartments. We opened up the wall to put a walkway opening and installed a steel header in the brick wall.

Apartment Combination opening through brick wall

Apartment Combination opening through brick wall and wet bar. UWS, Manhattan


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 with the right planning and a good team it can be a relatively painless process. 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 largest cost by far is the construction. The cost of combining apartments is going to depend on the extent of the renovation. How much work are you doing? If this is going to be a gut renovation, the cost will be much higher. Heating and air conditioning, for example, may be a major cost if you are re-configuring rooms. The level of quality will also affect the price. If you are working with high-end products and finishes, the price will increase.


Combining Apartments in NYC Examples:

Combining two apartments into one apartment

Brooklyn Apartment Combination & Renovation

In this example we joined 2 apartments in Brooklyn Heights. This project was to combine two condos into one, and do a gut renovation.

Combining Two Apartment into One NYC

Combining Two Apartment into One NYC


Combining Two Lofts in SoHo

This project is combining 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 are planning to combine apartments, the first step is to consult with an architect. Make sure you are working with highly qualified professionals for design and construction.

As an architect, I study design and construction, but these are complicated and quite involved issues. Every project is different and must be assessed on its own 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.

Good Luck with your apartment combination! If you are are looking to combine apartments in NY we would be happy to help. If you would like to speak with an architect, please feel free to contact Fontan Architecture directly.


Contact Fontan Architecture


External Sources:


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 15 years where he has designed renovations and new developments of various building types.