How To Combine Apartments In NYC

by | Dec 20, 2016 | Apartment Renovations, Renovations

Combining Apartments is a very popular process in New York. Two apartments next to each other 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.

I am an architect in NYC and owner of Manhattan 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 can be 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. Before you purchase two adjacent apartments you should always check with the building management company to see if they allow the joining of apartments most will. It is never to early to talk to an architect. People constantly call me before they close on the apartments and often we have even begun working on the design before closing.

You will definitely need to hire an architect when combining apartments and acquire permits from the NYC Department of Buildings. You also want to make sure the design works well. The apartment layout should not have thrown together feel. The apartment should flow properly, suite your needs, and fall within your aesthetic sensibilities.

Before doing any work in your apartment you will need to review your building’s alteration agreement.  To learn more 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 will be some that may. You will need to hire an architect to file the job with the NYC Department of Buildings, DOB, but more importantly you need 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 higher 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 filling. This is not always the case. The following are the requirements and regulations for combining apartments without changing the Certificate of Occupancy and filling 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 Combining apartments NYC rules 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 an 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

This first Item is for Condo’s 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 architectural plans and to submit an RP-602CA Form 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.


Combining Two Apartments Into One

The following items are for 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:
    • fire escapes
    • building stairs
    •  lobby
    •  building corridors, etc…


  • You can only have one kitchen when you combine apartments.
  • If the 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 for example.

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 that when you remove one kitchen you have plumbing there already. This can be a great opportunity to make a wet bar for the living room or add a bathroom if it suites your needs. If it does not then we can cap of the plumbing and gas and bury the riser and cap.

The picture below is of a bathroom we built in the place of a kitchen we removed on 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 the 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. Also we want to try to figure out if there are utilities at that location. Sometimes we find gas pipes in strange places during construction. If the wall is a load bearing wall 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 this determination.

The picture below is of an Upper West Side apartment combination we are working on. 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.

Opening a bearing wall Apartment Combo

Opening a brick bearing wall for an UWS Apartment Combo


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.


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. Combining apartments cost 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. For example heating and air conditioning may be a major cost if you are re-configuring rooms. The level of quality will also affect the price. If you are doing a very high end level 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 gut renovate.

Combining Two Apartment into One NYC

Combining Two Apartment into One NYC


Combining Two Lofts in SoHo

This project is one we are working on right now where we are combining two duplex lofts in SoHo to make one combined 6,500 square foot loft. We will upload photos when construction is complete. 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 firs step is to consult with an architect. Make sure you are working with well 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 provide a general overview of the topic.


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

Good Luck with you 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 us 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.