Combining apartments nyc

Combining Apartments In NYC

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


Combining Apartments

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.

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 ussually be filed by an architect or title company.


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.

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 including:
    • fire escapes
    • building stairs
    •  lobby
    •  building corridors, etc…


  • You can only have one kitchen.
  • 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.


Combining Apartments in NYC Examples

Combining two apartments into one

Brooklyn Apartment Renovation & Combination

In this example we joined 2 apartments in Brooklyn Heights.

Combining Apartments in NYC

Original 2 apartments

Combining two Apartments into one

2 Apartments Combined into 1


Good Luck with you apartment combination. 

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 Renovation Architectural Services page.

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