Combining Apartments in New York City: Scope, Planning, and Approvals

Combining apartments in New York City is one of the most effective ways to create a larger and more customized home within an established building. In many cases, it provides an opportunity to create a residence that would otherwise be unavailable in the market, particularly in prewar buildings, loft conversions, and highly desirable neighborhoods where large apartments are limited. Rather than adapting to an existing layout, apartment combinations allow homeowners to reimagine multiple smaller units as a single cohesive residence tailored to their lifestyle, priorities, and long-term goals.

Most apartment combinations in New York City are filed as Alteration Type 2 applications under DOB Technical Policy and Procedure Notice 3/97 (TPPN 3/97). While the regulatory framework for combining apartments is well established, successful projects require much more than obtaining permits and removing walls. Apartment combinations involve architectural planning, building approvals, structural evaluation, coordination with building management, and the careful reorganization of multiple units into a cohesive home. The most successful apartment combinations do not feel like combinations at all. They feel as though they were always intended to exist as a single residence.

I am Jorge Fontan, owner of Fontan Architecture, a New York City architecture firm specializing in high-end residential design. We have worked on apartment combinations, loft combinations, townhouse combinations, and full-gut residential projects throughout Manhattan and New York City. In this article, I discuss the architectural, regulatory, design, and construction considerations involved in combining apartments in New York City.

 

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Architectural Planning and Feasibility

Successful apartment combinations begin with planning and feasibility analysis long before construction starts. While many people focus on which walls can be removed, the more important question is whether the apartments can be transformed into a cohesive and functional home. Before design begins, we evaluate the building’s structural systems, plumbing infrastructure, mechanical systems, existing apartment layouts, and building-specific constraints to understand both the opportunities and limitations of the project.

For buyers considering the purchase of a vertical or adjacent apartment, involving an architect before the acquisition can be invaluable. We often help clients evaluate potential apartment combinations before they commit to a purchase, allowing them to better understand structural constraints, building requirements, filing implications, and realistic construction budgets. Early coordination with building management and review of alteration agreements can also help identify procedural requirements before significant financial commitments are made. We discuss this process in greater detail in our article on Consulting With an Architect Before Planning an Apartment Combination in New York City.

Apartment combinations are not limited to two units. We have worked on a variety of apartment and loft combinations throughout New York City, and we are currently designing a project on the Upper West Side that combines three separate condominium apartments into a single residence. Whether combining two apartments or multiple units acquired over time, the same principles of feasibility analysis, thoughtful planning, and cohesive design remain essential to the success of the project.

Feasibility is about more than determining whether apartments can be physically connected. We also evaluate how the resulting residence will function as a home. Circulation patterns, room organization, natural light, privacy, entertaining spaces, storage, and the relationship between public and private areas all influence the success of the final design. The most successful apartment combinations feel natural and intuitive, as though they were always intended to exist as a single residence.

By establishing these parameters early, we can develop a clear design strategy, identify the appropriate regulatory pathway, and create a roadmap for the project before construction begins.

 

Apartment Combinations and Cohesive Design

The greatest design challenge in an apartment combination is not physically connecting multiple apartments. The real challenge is creating a home that feels as though it was always intended to exist as a single residence. Successful apartment combinations require more than removing walls and opening new connections between units. We must carefully reorganize the home to establish clear circulation, logical relationships between spaces, and a cohesive architectural language that unifies the entire residence.

One of the principles that guides our work is the idea that the most refined homes feel natural and inevitable. We often describe this as effortless elegance. Although the completed home should feel intuitive, calm, and unforced, achieving that result requires extensive planning, coordination, and restraint. We carefully consider room proportions, circulation patterns, material transitions, architectural detailing, and lighting so that every element contributes to a unified composition. The goal is not to draw attention to individual design decisions, but to create a home that feels complete and cohesive as a whole.

Restraint is an important part of this process. Rather than introducing competing ideas or unnecessary complexity, we focus on developing a clear architectural vision and carrying it consistently throughout the residence. Material selections, architectural details, lighting integration, and spatial organization work together to establish continuity from one room to the next. When a home is thoughtfully composed, it feels natural and comfortable because every element belongs within the larger design.

The 4,000 square foot Manhattan apartment shown below reflects many of these principles. We custom designed the residence to create a cohesive environment where architecture, interiors, lighting, and building systems are fully integrated. Although the project involved combining two separate apartments, the completed home feels as though it was always conceived as a single residence. The organization of the spaces, continuity of materials, integrated lighting, and disciplined architectural detailing create a unified experience throughout the home. Most people visiting the apartment would never realize it was originally two separate units, which is ultimately one of the highest compliments an apartment combination can receive.

 

Approvals and Regulatory Framework

Apartment combinations in New York City require coordination with both the building and the New York City Department of Buildings. Before construction begins, we review the building’s governing documents, alteration agreement, existing Certificate of Occupancy, and the specific conditions of the apartments being combined. Establishing the appropriate approval and filing strategy early helps avoid delays and provides a clear path forward for the project.

Most apartment combinations in New York City are filed as Alteration Type 2 applications under DOB Technical Policy and Procedure Notice 3/97 (TPPN 3/97). This allows many combinations to proceed without obtaining a new Certificate of Occupancy, provided specific criteria are satisfied.

Apartment combinations may qualify under TPPN 3/97 when:

• The units are adjacent on the same floor or vertically connected across no more than two levels.
• Means of egress remain unchanged.
• Newly created rooms comply with applicable light and air requirements.
• Only one legal kitchen remains within the combined residence.

Projects that fall outside these parameters require a more extensive filing including an amended or new Certificate of Occupancy.

Beyond the Department of Buildings filing, apartment combinations typically require coordination with building management, co-op boards, condominium boards, and other project stakeholders. We work closely with our clients and the building throughout the approval process to address filing requirements, alteration agreement provisions, construction logistics, and other project-specific considerations. Establishing the correct regulatory pathway early allows the design and planning process to proceed efficiently while minimizing potential complications during approvals and construction.

 

Condominium-Specific Considerations

Condominium apartment combinations involve an additional layer of coordination beyond the Department of Buildings filing process. Unlike cooperative apartments, condominium units are separate legal properties with individual tax lots. When condominium apartments are combined, we must also coordinate the consolidation of the tax lots so that the legal property records align with the completed residence.

Before DOB issues an approval for a condominium apartment combination, we must obtain a Tentative Tax Lot from the New York City Department of Finance. This process requires architectural documentation and coordination with the condominium’s governing structure. Depending on the building, the process may also involve amendments to the condominium’s apportionment schedule and coordination with the managing agent, condominium board, and building attorney.

Because tax lot mergers are a unique aspect of condominium apartment combinations, we discuss this process in greater detail in our article on Tax Lot Mergers for Condo Apartment Combinations in New York City.

Cooperative apartment combinations follow a different approval structure and do not require tax lot consolidation. Regardless of whether the project is located in a condominium or cooperative building, we coordinate the architectural, regulatory, and administrative requirements necessary to move the project through approvals and construction.

 

Structural Assessment and Wall Removal

Many apartment combinations require the removal or modification of existing walls to create a more functional and cohesive layout. Before we begin developing a design, we evaluate the existing structure to determine which walls can be removed, which walls are load-bearing, and how structural modifications may affect the project. Understanding these conditions early helps establish realistic design opportunities and prevents costly surprises during construction.

In many prewar buildings and loft conversions, structural walls and critical building systems are concealed within existing partitions. We often encounter plumbing risers, gas lines, electrical infrastructure, and other building systems that influence how apartments can be reconfigured. By carefully evaluating these conditions during the planning phase, we can develop design solutions that work within the realities of the existing building while supporting the overall goals of the project.

When structural modifications are required, we work closely with structural engineers to develop appropriate solutions. In some cases, this may involve introducing steel beams or other structural reinforcement to support the building while opening up the floor plan. Rather than treating these interventions as isolated engineering requirements, we integrate them into the overall architectural design so that the structure, layout, and spatial organization work together as part of a cohesive residence.

 

Reconfiguring the Secondary Kitchen

One of the most common design opportunities in an apartment combination occurs when we remove a secondary kitchen. Because only one legal kitchen remains within the combined residence, the former kitchen location often becomes valuable space that can be repurposed to better support the overall design of the home.

Since plumbing, drainage, gas, and ventilation infrastructure are often already present, we frequently transform former kitchen areas into bathrooms, laundry rooms, utility spaces, storage areas, or other support spaces. The existing infrastructure can create opportunities to improve functionality while minimizing the need for extensive modifications to building systems.

Rather than viewing the removal of a secondary kitchen as a simple code requirement, we treat it as a design opportunity. We evaluate how the space can best contribute to the organization and functionality of the residence as a whole. When thoughtfully integrated into the overall design strategy, the former kitchen can help improve circulation, support the programmatic needs of the home, and contribute to a more cohesive and efficient floor plan.

Since plumbing, drainage, and ventilation infrastructure are often already present, we frequently transform former kitchen areas into bathrooms, laundry rooms, utility spaces, storage areas, or other support spaces. We have converted many former kitchens into bathrooms and laundry rooms in apartment combination projects throughout New York City. The existing infrastructure can create opportunities to improve functionality while minimizing the need for extensive modifications to building systems.

 

Apartment Combination Scope of Work

The cost of combining apartments in New York City varies significantly depending on the size of the project, the condition of the existing apartments, the level of customization, and the requirements of the building. Because every apartment combination is unique, there is no universal cost per square foot or standard budget that applies to all projects.

Many apartment combinations involve much more than connecting adjacent units. We often reconfigure layouts, relocate kitchens and bathrooms, upgrade electrical systems, modernize plumbing, improve HVAC systems, install custom millwork, and completely redesign the interiors. As a result, apartment combinations frequently resemble full gut renovations rather than simple alterations.

Some of the primary factors that influence cost include:

• Extent of demolition and structural modifications
• Mechanical, electrical, and plumbing upgrades
• Kitchen and bathroom renovations
• Custom millwork and integrated storage
• Finish level and material selections
• Building-specific requirements and construction logistics
• Overall project size and complexity

One of the advantages of involving an architect early in the process is developing a realistic understanding of project scope and budget before major commitments are made. We help our clients evaluate design goals, building constraints, and construction requirements so that the project can be planned with a clear understanding of the likely costs involved.

 

Frequently Asked Questions About Combining Apartments in NYC

Do I need a new Certificate of Occupancy?

Many apartment combinations in New York City can be filed as Alteration Type 2 applications under TPPN 3/97 and do not require a new Certificate of Occupancy. Projects that fall outside the parameters of TPPN 3/97 require a different filing strategy including an amended or new Certificate of Occupancy.

Can I combine apartments in a co-op?

Yes. Apartment combinations are commonly performed in cooperative buildings throughout New York City. These projects require board approval and must comply with the building’s alteration agreement and construction requirements.

Does my building’s alteration agreement affect an apartment combination?

Absolutely. Alteration agreements play an important role in apartment combinations. They establish the building’s requirements for approvals, construction procedures, insurance, access, and project coordination. We review alteration agreements early in the planning process to understand the building’s requirements and identify any restrictions that may influence the design or execution of the project.

How much does it cost to combine apartments in Manhattan?

The cost of an apartment combination depends on the size of the apartments, the extent of the renovation, building constraints, structural modifications, and the level of customization. Many apartment combinations resemble full gut renovations because they involve significant reconfiguration of layouts, kitchens, bathrooms, building systems, and interior finishes. We help our clients establish realistic project budgets during the early planning and feasibility stages.

Should I consult an architect before purchasing an adjacent apartment?

Yes. We frequently work with clients before they purchase neighboring apartments to evaluate feasibility, building requirements, potential layouts, structural constraints, and likely construction costs. Early consultation can help identify opportunities and limitations before significant financial commitments are made.

Can condominium apartments be combined?

Yes. Condominium apartment combinations are common in New York City. In addition to the architectural and regulatory requirements associated with the renovation itself, condominium combinations typically require the consolidation of tax lots and coordination with the condominium’s governing structure.

 

Working With an Architect on an Apartment Combination

Combining apartments in New York City requires much more than connecting adjacent units. Successful apartment combinations require architectural planning, feasibility analysis, regulatory approvals, coordination with building management, and careful design development. Every project presents unique opportunities and constraints that must be evaluated based on the building, the existing apartments, and the goals of the homeowner.

The most successful apartment combinations do not feel like combinations at all. They feel as though they were always intended to exist as a single home. Through careful planning, thoughtful design, technical expertise, and close coordination throughout the project, we work to transform multiple apartments into cohesive residences that feel natural, functional, and enduring.

For homeowners considering combining apartments in New York City, involving an architect early in the process can help establish feasibility, clarify regulatory requirements, identify design opportunities, and create a roadmap for a successful project.

At Fontan Architecture, we provide full-service architectural design for apartment combinations throughout New York City. We work with clients from the earliest stages of planning, including pre-purchase consultation and feasibility analysis, through design development, approvals, construction documentation, and construction administration. Our goal is to guide the entire process while creating a residence that is tailored to the client and thoughtfully integrated into the existing building.