Feasibility of Combining Apartments in Midtown Towers

Thinking about turning two Midtown apartments into a single, seamless home? You are not alone. In many Midtown towers, combining units can be a smart way to gain square footage, improve flow, and elevate resale potential. This guide shows you how to gauge feasibility, what approvals and costs to expect, and how to protect value from day one. Let’s dive in.

What makes a combination feasible in Midtown

The most straightforward combinations join two apartments that sit side by side on the same floor with a shared party wall. Vertical combinations to create a duplex are possible but usually more complex. Before you spend on plans, confirm whether the building and the NYC code framework will allow your idea.

Horizontal vs vertical combinations

• Horizontal combinations typically remove a non-structural party wall or create a rated opening. These usually carry lower cost and fewer structural risks.
• Vertical combinations require a new internal stair, which means cutting the concrete slab. That triggers structural engineering, permits, and longer timelines. It can also affect egress and fire protection.
• Non-contiguous apartments that are separated by corridors or different wings are rarely practical without very costly work.

Early checkpoints and who to call first

Start with documents and a quick technical review before you sketch layouts.

• Pull the building’s Certificate of Occupancy and floor plans. The C of O drives unit count and code triggers. Review the city’s guidance on the Certificate of Occupancy.
• Confirm whether the party wall is loadbearing and whether it is a fire partition. This drives structural scope and firestopping needs.
• Sequence your experts: building management or listing broker, then a licensed architect, then a structural engineer. Engage an NYC expeditor or permitting attorney for filings, and a contractor for realistic pricing.
• Most work needs permits. See the NYC Department of Buildings overview of work permits and alterations and alteration projects.

Technical factors to plan for

Your plan must fit the building’s structure and systems. Midtown high-rises often have concrete slabs, centralized risers, and strict fire protection protocols.

Structural

• Identify loadbearing elements before planning openings. Removing or altering loadbearing walls requires a structural engineer, stamped drawings, and Department of Buildings review. Temporary shoring and new beams may be needed.
• For vertical combinations, slab openings for stairs require structural calculations, detailing, and careful sequencing. Expect higher cost and longer lead times.
• Curtain wall or column grids in Midtown towers can limit how open your layout can be.

Plumbing and sanitary

• Kitchens and baths must tie into sanitary stacks. Moving wet areas can require core drilling or rerouting within tight chases. Shared stack work often needs DOB approval and building coordination.
• Stack capacity and slope matter. Adding fixtures or reconfiguring drains can impact neighbors and may not be allowed without analysis.
• Many Midtown buildings have limited space for new piping runs. That can constrain ambitious layouts.

Electrical and HVAC

• Combining panels or re-metering may be needed. All electrical work must be done by a licensed electrician and may require filings.
• Central HVAC buildings may only need duct and control changes. In-unit systems like PTAC or splits may require additional capacity or new lines.
• Older buildings can include asbestos-containing materials. Any disturbance must follow abatement rules.

Egress and fire protection

• Changes that affect unit count, internal stairs, or room configuration can trigger egress and life-safety reviews. Refer to the NYC Construction Codes for egress and fire rating requirements.
• Party walls are often fire rated. New openings must maintain required ratings and proper firestopping.
• If sprinkler or fire alarm systems are modified, the work will require coordination with the building and city agencies. See FDNY guidance on fire sprinkler systems and fire alarm systems.

Certificate of Occupancy and unit count

• If the combination changes the number of dwelling units shown on the C of O or alters the unit’s legal use, the project will require filings to update the C of O. This can add review time.
• Always obtain the current C of O and relevant floor plans at the outset. The DOB provides public guidance on Certificates of Occupancy.

Co-op and condo approvals in Midtown

Approvals run on two parallel tracks: the building and the city. Co-ops and condos each have unique processes.

Co-op boards: what to expect

• Most co-ops require a formal renovation package. Expect to submit stamped plans, contractor licenses and insurance, a construction schedule, and deposits for building protection.
• The proprietary lease can set limits on bedroom counts or unit configurations. Shares and maintenance may be reallocated after a combination.
• Timelines vary. Some boards respond in 4 to 8 weeks, others take longer. Co-ops have broad discretion and can impose conditions or deny work.

Condos: how it differs

• Condos also require a renovation application and deposits, though the process is usually more standardized.
• You own the unit in fee simple, so there are fewer share-related hurdles. Building protection and insurance requirements still apply.

City permits: DOB and FDNY

• Most combinations with structural, plumbing, or egress changes need permits. Plans must be stamped by a licensed architect or engineer, then reviewed by the DOB. Start with DOB’s overview of work permits and alterations.
• If your plan modifies sprinklers, fire alarms, or egress, FDNY review and inspections may be required. See FDNY guidance on fire code and systems.
• Some buildings fall under the New York State Multiple Dwelling Law. You can reference the Multiple Dwelling Law for building class considerations.

Lenders, title, and taxes

• If you have a mortgage, notify your lender. Many lenders require consent before material alterations. Renovation financing or draw schedules may apply.
• Combining units can require changes to the legal description and, in co-ops, to proprietary lease shares.
• Property assessments can change after the city updates records. Tax timing can lag actual completion.

Typical approval timeline

• Board application review: 2 to 12 weeks, often longer for co-ops.
• DOB plan prep and submission: 2 to 8 weeks.
• DOB review and permit issuance: 4 to 12 weeks or more. Complex structural or use changes take longer.
• FDNY reviews can add weeks if life-safety systems are modified.
• Many Midtown combinations need 3 to 9 months of approvals before work begins.

Cost ranges and timelines

Budget and duration depend on scope, building rules, and the extent of structural and MEP work.

Budget ranges to expect

• Minor horizontal combination with light MEP and finishes: roughly 40,000 to 150,000 dollars.
• Moderate remodel that includes a kitchen, 1 to 2 baths, and electrical or HVAC work: roughly 150,000 to 400,000 dollars.
• Major combination with slab cutting for a stair, significant structural work, and full MEP reconfiguration: 400,000 to 1,500,000 dollars or more.
• Midtown construction costs trend high due to labor, elevator protection, debris logistics, and building monitoring.

Project timeline from start to finish

• Pre-design and feasibility: 1 to 3 months.
• Design and board package: 1 to 3 months.
• Board approval: 1 to 3 months or longer for co-ops.
• DOB or FDNY permitting: 1 to 6 months.
• Construction: 2 to 9 months. Horizontal combos are faster, duplexes are longer.
• From first inquiry to completion, many Midtown projects run 6 to 18 months.

Resale strategy and risk

Many buyers combine units to create a larger, better planned home that commands a higher price and, in some buildings, a higher price per foot. The uplift depends on building reputation, line, views, and layout quality. In some cases, heavy structural scope or hyper-custom layouts can erode returns.

• Work with a local agent early to study sales of combined units in the same building or immediate area.
• Keep the layout functional and finishes high quality yet neutral.
• Avoid overcapitalizing if the building or line does not support the target price point. Market timing in Midtown can matter if demand shifts.

A practical Midtown checklist

• Obtain the C of O, building floor plans, and renovation rules.
• Retain a licensed architect and structural engineer for an early feasibility read.
• Meet building management to confirm policies and likely conditions.
• Line up contractor bids, insurance, and a construction deposit budget.
• Hire an NYC expeditor or permitting attorney for filings.
• Set a 15 to 25 percent contingency for unforeseen structural or code issues.
• Coordinate lender consent and plan for any unit description updates.
• Pre-plan logistics: elevator booking, debris paths, and worker access.

Common pitfalls to avoid

• Assuming a party wall is non-structural without analysis.
• Underestimating plumbing stack limits and the cost of rerouting.
• Investing in full design before getting board pre-feedback.
• Skipping lender consent or title updates when combining legally.
• Forgetting building-required deposits, monitoring fees, or extended schedules.
• Performing unfiled work, which can lead to fines and future sale issues.

Next steps

If you are exploring a combination in a Midtown co-op or condo, start with documents, a quick architectural read, and a candid pricing review. A board-savvy plan with realistic costs and timelines will protect both your time and your equity. For discreet guidance on feasibility, board strategy, and resale positioning, request a conversation with Francine Crocker.

FAQs

How do I know if my Midtown units can be combined?

• Start by confirming that the apartments are contiguous and by reviewing the building’s C of O and renovation rules. An architect and structural engineer can assess the party wall, stacks, and egress.

What permits are needed to combine two Midtown apartments?

• Most combinations with structural, plumbing, or egress changes require DOB permits. Review NYC’s work permits guidance and plan on stamped drawings.

Is combining easier in a condo than a co-op in Midtown?

• Condos often run a more standardized process. Co-ops can be more discretionary and may take longer or impose conditions, especially for vertical combinations.

Will a vertical duplex in a Midtown tower cost more?

• Usually yes. Cutting the slab for a stair, structural reinforcement, and life-safety impacts make vertical projects more expensive and slower than horizontal ones.

Could my property taxes change after I combine units?

• Possibly. Assessments can change once records are updated, though timing can lag the completion date.

Do I need FDNY involvement for a simple horizontal combination?

• You may not if you do not modify sprinklers, fire alarms, or egress. If you do, FDNY review and inspections can be required. See FDNY guidance on fire code and systems.