Apartment Combination NYC

Combining Apartments In NYC

(Last Updated On: December 30, 2019)


Apartment combinations are very popular in New York. Combining Apartments in NYC does not usually require any change to a Certificate Of Occupancy. Two apartments next to each other can be combined to make one apartment in NYC without getting a new C Of O 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.

If you are looking to combine apartments in NYC below we will outline some of the things you should know.


Combining Apartments

Combining apartments in NYC is quite common. This trend has become very popular because it is easier to buy the neighbors apartment when they move than it is to find a new larger apartment. Combining two apartments into one is the most convenient way to double your apartment size. Here are some of the protocols for joining apartments in Co-Ops and Condos in New York City. Before you purchase two adjacent apartments you should always check with the building management company to see if they allow the joining of apartments.

Combining apartments in NYC into one is a relatively common practice but there are some things you will need to know. You will definitely need to hire an architect when combining apartments and file the work with the NYC Department of Buildings.

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 do. You will need to hire an architect to file the job with the NYC Department of Buildings, DOB. The biggest point of confusion 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. A certificate of occupancy.

  • 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.
  • 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.


Protocol For Combining Apartments in NYC

NYC DOB Combine Apartments 

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 an 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”

Criteria for Combining Apartments without a change to the Certificate Of Occupancy and Filing an Alt 2 with DOB.

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

  • Architect Must File 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


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. This will usually be filed by an architect or title company.


Combining Two Apartments Into one

The following items are for Co-Ops and Condominiums

Type of Apartment Combinations Allowed as 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 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.


If you are planning on combining apartments in NYC you will need an architect make sure to hire licensed, insured, and qualified professionals.

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 other work are you doing? If this 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.


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.





Brooklyn Co-Op Apartment Combination

This project was combining two Co-Op apartments in Brooklyn.



Manhattan Apartment Combination Co-Op

Apartment Combination in a Manhattan Co-Op building on the Upper East Side.

Apartment Combination NYC Co-Op

Combining Co Op Apartments



Contact Fontan Architecture


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. Additionally if you would like to learn more about our services please check out our Apartment Combination Architects services or Apartment Renovation Architectural Services page.


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