Many buyers in New York City consider purchasing adjacent apartments with the intention of combining them into a larger residence. Apartment combinations are an effective way to create a more spacious home within a given building. While the concept appears straightforward, the feasibility of combining apartments depends on many factors related to the building, the apartments themselves, and applicable regulations. Apartment combinations must also fulfill the owner’s needs while creating a cohesive home designed for both aesthetics and function.
Apartments in New York City can be combined horizontally or vertically when the physical conditions allow for construction that complies with applicable building codes. This is also contingent on the policies of the building and the approval of the condo or co-op board for the proposed alteration.
At Fontan Architecture, we have worked on many apartment and loft combinations throughout New York, including helping property owners assess apartments for potential combination. In many cases this evaluation begins before a purchase, helping buyers understand the opportunities and constraints of a property. In some situations it is beneficial to consult with an architect before planning an apartment combination to review feasibility and building conditions. In this article we outline several key factors that influence whether apartments can be combined in New York City.
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Building Policies and Board Approval
The first thing to determine when planning to combine apartments is whether the condominium or co-op board allows combinations in the building. Most buildings will authorize apartment combinations, but approval is always required and the board may have specific policies governing the alteration. The review and approval process will vary between buildings, as will the specific regulations and limitations imposed by the board.
For example, I served as the architect for the first apartment combination in a particular prewar building where no units had ever been combined in over one hundred years. Even though the proposed design did not receive a single architectural objection during review, the approval process took an unusually long time simply because the building had no precedent for this type of alteration. The project was ultimately approved, but the review timeline was significantly extended by the board.
Condo and co-op boards in New York City each have their own rules governing alterations. Some buildings impose strict limitations, while others allow greater flexibility. Apartment combinations must be reviewed and approved by the board in accordance with the building’s alteration agreement and other requirements. In most buildings, particularly in Manhattan, this process involves submitting a full set of architectural drawings and supporting documentation including contractor proposals, insurance certificates, Department of Buildings filing documentation, and Landmarks Preservation Commission approvals where applicable. These materials are typically reviewed by the building’s architect or engineer, whose services are usually billed to the applicant as part of the alteration review process.
Physical Conditions of the Apartments
In order to combine apartments, the units must be adjacent either horizontally or vertically. An evaluation of the existing conditions is necessary to understand how the apartments are constructed and how they connect within the building. This assessment includes identifying structural elements such as columns, beams, and bearing walls, as well as building infrastructure including plumbing, gas, electrical systems, HVAC equipment, and vertical risers.
Structural conditions play a significant role in determining how apartments can be combined. In buildings with concrete floor slabs, it is often possible to cut through the slab and create a new opening with proper structural engineering and reinforcement. In older masonry buildings it may also be possible to create openings in bearing walls, provided that the structural loads are properly supported through new beams or other structural interventions.
Construction methods vary widely between buildings. Many newer high-rise buildings rely on structural systems of steel or concrete columns and beams with concrete floor slabs, which typically means there are fewer internal bearing walls between apartments. Older buildings may rely more heavily on masonry bearing walls, which can influence how the apartments can be connected and how the new layout can be organized. A thoughtful structural and mechanical assessment will lead to a clear determination of the available options for combining the units.
Structural elements and utilities can influence the layout and overall design of the combined apartment. Thoughtful planning is necessary to achieve a cohesive spatial organization and a clear sense of circulation in the final design.
Plumbing and Kitchen Removal Considerations
When combining apartments, one of the units will typically have its kitchen removed. This space can often be repurposed for another function that benefits from existing plumbing infrastructure, such as a wet bar, bathroom, or laundry room. In other cases, the plumbing can be capped and the area converted into dry living space, depending on the desired layout and the building’s requirements.
All utilities must be carefully evaluated when planning an apartment combination. Plumbing systems in residential buildings rely on vertical risers and stacks that serve multiple apartments throughout the building. These risers can run within the walls of individual units and may influence how spaces can be reconfigured.
Understanding the location of plumbing risers, waste stacks, gas lines, and other utilities is an important part of assessing how the combined apartment can be organized. The placement of these components can affect where kitchens, bathrooms, and other plumbing fixtures can be located within the new layout as well as where openings through the two apartments can be created.
Luxury bathroom designed as part of an apartment combination renovation in New York City.
Building Code Requirements
There are many building code considerations that apply to apartment combinations in New York City. One important guideline frequently associated with apartment combinations is Technical Policy and Procedure Notice 3/97 (TPPN 3/97) issued by the New York City Department of Buildings. We discuss this regulation and other approval requirements in more detail in our guide on combining apartments in New York City. This notice provides guidance for combining apartments while maintaining the same number of legal dwelling units in the building without requiring a new Certificate of Occupancy.
One design implication of this condition is that the entrances to the original apartments are maintained unless you obtain a new Certificate of Occupancy for the building. When apartments are combined without a change to the Certificate of Occupancy, the existing entry doors are generally required to remain in place. As a result, it is common for combined apartments to retain two or more entry doors.
This illustrates how building regulations can directly influence the design of an apartment combination. Code requirements may affect circulation, entry conditions, and how the combined apartment is organized. Understanding these constraints early in the design process helps determine whether an apartment combination is feasible and how the new layout can be developed.
Budget Considerations
The budget and timeline for combining apartments can vary significantly depending on the scope of work. In our projects, apartment combinations typically involve a full gut renovation of the combined space, which includes replacing finishes, updating building systems, and reconfiguring the layout to create a cohesive new residence.
On most of our apartment combination projects, the full renovation scope is the primary driver of construction cost rather than the act of connecting the apartments themselves. Structural work, plumbing relocation, and new mechanical systems may contribute to the budget, but the overall renovation typically represents the largest portion of the project.
For this reason, evaluating the potential scope of renovation is an important part of assessing the feasibility of an apartment combination.
Evaluating the Feasibility of Apartment Combinations in NYC
Apartment combinations in New York City can create exceptional residential spaces, but the feasibility of combining units depends on a range of architectural, regulatory, and building-specific factors. Board policies, physical conditions, building infrastructure, code requirements, and the scope of renovation all influence whether two apartments can realistically be combined into a single residence.
For buyers and property owners, evaluating these conditions early can help clarify the opportunities and limitations of a potential combination. Understanding the building’s policies, reviewing the structural and mechanical systems, and considering the regulatory framework can help determine whether a project is feasible and how the design may be developed.
At Fontan Architecture, we regularly work on apartment combinations, including pre-purchase assessments, full architectural design, and project execution. Careful evaluation at this stage can provide clarity on what is possible and help guide the design and planning process for a successful apartment combination project in New York City.
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Jorge Fontan, AIA, is an architect and founder of Fontan Architecture based in New York City. The firm focuses on residential design, including new homes and extensive renovations for discerning clients. Through collaborative dialogue that draws on the individuality of each client, projects develop as distinct architectural responses guided by thoughtful planning, precise detailing, and a commitment to creating enduring value.
