Love your Manhattan neighborhood, but hate how tiny your floorplan is? For some NYC homeowners, dreaming of more space doesn’t necessarily mean you need to leave the area you love. Instead, you might be able to purchase one of your neighboring units and merge the two apartments into a single, expansive home for yourself.
Apartment combination can be an excellent solution for staying in place with a bigger footprint. When done thoughtfully, combining apartments can produce a truly unique home that feels custom-built.
While the concept is fairly straightforward, the logistics aren’t: these projects involve a surprising amount of architectural planning, regulatory approvals, and design strategy.
Your ideal apartment combination probably isn’t just adding a door between spaces, so let’s dive into how you can transform two separate floor plans into a cohesive home with natural circulation, balanced proportions, and integrated building systems. Here’s what homeowners like you in the Big Apple should know before embarking on an apartment combination project:
Why combine apartments?
One word – space. Lots of older buildings (think prewar co-ops and historic condominiums) were designed with smaller units that don’t exactly match modern expectations for family living or entertaining.
Combining apartments allows homeowners to expand their living environment while staying in the building and neighborhood they already value. Rather than relocating to a larger apartment elsewhere, owners can often purchase an adjacent unit and create something entirely custom.
Several motivations typically drive these combination projects:
- Growing households. Families often need additional bedrooms, offices, or flexible living areas to accommodate more individuals.
- Lifestyle upgrades. Larger kitchens, formal dining areas, or expanded entertaining spaces become possible when you add space. Dedicated game room? Home gym? The world is your oyster.
- Long-term investment. Well-designed larger apartments often command higher resale values in desirable Manhattan neighborhoods.
The Manhattan residential market also places a premium on spacious apartments. According to data from the Nationwide Mortgage Bankers, larger homes with flexible layouts (that can accommodate roomy home offices) have grown significantly in demand as remote and hybrid work became more common. That shift has made apartment combinations an increasingly attractive option for urban homeowners.
Key regulatory and structural considerations when merging units
Before any demolition or design work begins, architects need to evaluate how feasible an apartment combination is. New York City has strict regulations governing residential alterations, and each building adds its own set of requirements.
If you already have an experienced NYC architect, then they can guide you through this process. (And if you’re still in the research phase, here are some questions to help guide your decision.)
Building / co-op / condo board approvals and regulations
If you live in a condominium or co-op, your first round of approval typically comes from your building itself. Co-op boards and condominium boards often maintain strict alteration agreements that dictate what types of renovations are permitted. Some example requirements include:
- Architectural plan submissions for board review
- Construction hour restrictions
- Noise and dust mitigation procedures
- Insurance and contractor qualification requirements
In co-op buildings, board approval can sometimes be the most unpredictable step in the process. Some boards are enthusiastic about well-designed combinations and their potential to increase property value, while others limit the number of units any single owner may control.
For condominium buildings, an additional consideration is tax lot consolidation. When two condo units merge into a single residence, the ownership records often need to be updated through the city’s finance department.
Projects also require filings with the New York City Department of Buildings. Depending on the scope, apartment combinations may qualify as an Alteration 1 or Alteration Type 2 filing, though more extensive changes can require updated certificates of occupancy.
Structural walls and load-bearing considerations
Once the paperwork has been sorted out, it’s time to think logistics. One of the most important questions in any combination project: is the wall between your two apartments structural?
Load-bearing walls support the building’s structural system. Removing or modifying them requires engineered reinforcement, aka scaffolding like steel beams or columns. Scaffolding will generally need to be designed by a structural engineer – don’t worry, though, this is something your architect can help coordinate.
What if your wall isn’t structural? That’s great, but there are a couple potential other essential building pieces that could still be in your shared wall, like:
- Plumbing risers
- Gas lines
- Electrical conduits
- HVAC ducts
Identifying these elements early on prevents nasty surprises during construction and could guide the architectural layout of your combined residence.
Mechanical, plumbing, and electrical integration
Merging two apartments also means merging two sets of building systems. Electrical service, plumbing fixtures, HVAC equipment, and ventilation systems must be carefully integrated into a single coordinated design.
New York City residential codes typically allow only one full kitchen per apartment. As a result, the secondary kitchen is usually removed or repurposed. Fortunately, because plumbing lines already exist in that location, architects can easily transform these spaces into bathrooms, laundry rooms, or service pantries.
Mechanical integration can also present some new opportunities. Some combination projects introduce improved climate control systems that improve comfort throughout the expanded home.
Design ideas for merged apartments
Once regulatory and structural feasibility is confirmed, the creative portion of the project begins. This is the fun part; it’s where you get to define what the flow of your final home looks like. You can start incorporating interior design here.
Creating coherent circulation and flow
The most common design mistake in apartment combinations is leaving the original layouts largely intact. Without rethinking circulation, the final product might feel fragmented and awkward.
Architects typically redesign the floor plan to create intuitive pathways between rooms. Hallways may shift, doorways relocate, and rooms are expanded to establish a natural flow through the home.
A well-planned circulation strategy ensures that the combined apartment feels intentional rather than stitched together.
Zoning public vs private spaces in merged layouts
“Zoning” sounds a little stiff, but in a merged layout, it can be useful to take the reorganization to delineate public and private areas. For example, lots of luxury apartment combinations reorganize the layout into two primary zones:
Public spaces
- Living rooms
- Dining rooms
- Kitchens
- Entertainment areas
Private spaces
- Bedrooms
- Home offices
- Dressing rooms
- Family lounges
This separation allows you to entertain guests comfortably while also maintaining privacy for daily life. Some people love the delineation method – but maybe you’d rather create a more open environment throughout. That’s also achievable with an apartment combination!
Maintaining aesthetic harmony
One of the biggest visual challenges in apartment combinations is maintaining consistency. Your original unit and its neighbor might have been renovated decades apart – which equals mismatched flooring, moldings, ceiling heights, etc.
Architects typically treat the project as a full interior redesign to create continuity across the new residence. This might include:
- Matching or replacing flooring throughout the apartment
- Designing new millwork and trim profiles
- Aligning ceiling details and lighting plans
- Introducing cohesive material palettes (think wood shades, natural stone, etc.)
The goal is to ensure that the apartment reads as one cohesive space.
Hiring an architect — what to expect during a combination project in Manhattan
Apartment combinations in New York City almost always begin with an architectural feasibility study. Before purchasing an adjacent unit or committing to construction, homeowners benefit from understanding the structural and regulatory constraints of the building.
An architect typically performs several early-stage services:
- Reviewing building drawings and alteration agreements
- Evaluating structural walls and mechanical systems
- Developing preliminary layout concepts
- Identifying required city filings and permits
During the design phase, the architect prepares construction documents used for both board approvals and Department of Buildings filings. Once construction begins, your architect will also coordinate with contractors to ensure the project follows the approved design. (Learn more about how architects and builders collaborate.)
Given the complexity of these renovations, early architectural involvement often saves both time and money by preventing redesigns later in the process.
Potential challenges and how to mitigate them
We never said this would be easy. Apartment combinations are complex renovations, and unexpected conditions are common. However, a little thoughtful planning can significantly reduce your risks.
Common challenges include:
Hidden building infrastructure
Older buildings often conceal plumbing, gas lines, or electrical risers inside walls. Detailed investigation during design helps anticipate these conditions.
Building restrictions
Alteration agreements may restrict plumbing relocations or impose strict construction schedules. Early communication with building management helps avoid delays.
Uneven floors or structural irregularities
Prewar buildings sometimes have floors that slope or ceilings that differ slightly between units. Architects can resolve these issues through subtle design solutions such as adjusted ceiling planes or custom millwork.
Proper planning and experienced project management make a dramatic difference in keeping a combination project on schedule.
There’s also one elephant in the room we haven’t addressed: budget. That’s because luxury apartment renovation costs often vary widely depending on the individual home and which particular changes are made. Our guide to understanding luxury apartment remodeling costs might give you a good starting point to begin with, though.
How a total home remodel during combination improves your value
Most apartment combinations evolve into full-scale gut renovations. While that may sound extensive, it often produces the best long-term results.
Rather than preserving outdated layouts or finishes, a complete redesign allows homeowners to optimize the apartment for modern living. Larger kitchens, expanded bathrooms, integrated storage, and upgraded building systems all contribute to a more functional home.
These improvements can also influence resale value. Well-designed larger apartments tend to command a premium in many Manhattan neighborhoods because they offer a level of space rarely available in the city’s housing inventory.
A thoughtfully executed combination therefore enhances both lifestyle and long-term property value.
Get in touch with K-DA today
Combining two Manhattan apartments is one of the most rewarding ways to create a truly bespoke home in New York City. With careful architectural planning, regulatory expertise, and thoughtful design, two separate units can become a seamless residence tailored to your lifestyle.
At K–DA, we specialize in complex residential renovations throughout Manhattan, including apartment combinations, gut renovations, and luxury interior transformations. Our team guides clients through every stage of the process, from feasibility studies and board approvals to design development and construction oversight.
If you’re considering merging apartments in your building, we’d be happy to explore the possibilities with you. Contact us today.
FAQs: Combining apartments in Manhattan
Is it legal to combine apartments in Manhattan?
Yes, apartment combinations are legal in many Manhattan buildings, but they require approvals from both the building and the city. If you live in a co-op or a condo, you may also need approval from your co-op board or condo association, and the project must always comply with New York City building codes.
If that sounds like a lot of paperwork, don’t worry. Your architect will generally handle the required filings and permits.
Do I need a permit to combine two apartments?
Yes. Apartment combinations require permits filed with the New York City Department of Buildings. The specific filing type depends on the scope of the work.
Can any two apartments be combined?
Not always. Structural walls, plumbing locations, and building rules can limit what is possible. A feasibility study performed by an architect helps determine whether a combination is practical before you purchase or renovate an adjacent unit.
However, explore your options: you may be able to combine apartments with an upstairs or downstairs neighbor, not just neighboring units on your left or right.
What happens to the second kitchen when combining apartments?
In most cases, the second kitchen must be removed because New York City residential regulations typically allow only one full kitchen per dwelling unit. However, the plumbing connections in that space can often be repurposed for a bathroom, laundry room, or wet bar.
Is combining apartments worth it in Manhattan?
This is a personal choice for you. For many homeowners, yes, they love the ability to stay in their neighborhood while creating a larger, custom residence. When designed well, merged apartments often attract strong resale interest due to the rarity of spacious homes in Manhattan.
