How to Combine Apartments in NYC—Without Needing a New Certificate of Occupancy

[Michael Genari]

In New York City, combining apartments is a strategic way to create larger, more functional living spaces—especially for condo owners, co-op shareholders, and real estate investors. If done correctly, this type of renovation does notrequire a new or amended Certificate of Occupancy (C of O). But to stay in compliance with NYC Department of Buildings (DOB) rules, every detail must be handled precisely.

Let’s walk through how it works under DOB’s Technical Policy and Procedure Notice #3/97 (TPPN 3/97), and why having the right professionals on your team is key.

C of O Not Required—When You Follow TPPN 3/97

TPPN 3/97 allows apartments in multi-family buildings to be legally combined—without triggering a C of O update—if:

• The overall number of primary living spaces (such as bedrooms, living rooms, dens, etc.) stays the same or decreases
• You don’t alter building egress (staircases, corridors, exits)
• The work is limited to interior construction

This provision applies to all multiple dwellings in NYC, including old law, new law, converted, and new code buildings.

What You’ll Need to File

1. Architectural Drawings from a Registered Architect (RA) or Professional Engineer (PE)
2. Alteration GC Application for general construction items like partition changes or internal stairs
3. Alteration PL Application for plumbing work—particularly when repurposing or capping kitchen fixtures
4. Letter of Completion issued by DOB when the work is signed off, confirming no new or amended C of O is needed

TPPN 3/97 Requirements—Simplified

• Same or Adjacent Floors Only: Combinations are limited to apartments located on the same level or directly above/below each other. Duplexes are permitted via internal staircases—but only across two floors.
• Living Room Count Must Not Increase: The new layout must have the same or fewer primary living spaces, excluding kitchens and bathrooms.
• Light & Air Compliance: All habitable rooms must meet natural light and ventilation requirements. Existing non-compliances can't get worse.
• No Egress Modifications: Corridors, staircases, and fire escapes must remain untouched.
• One Kitchen Rule: You must remove the second kitchen or repurpose its plumbing for another legal use (e.g., wet bar, washer/dryer, bathroom).
• For Condos: A new tentative tax lot number must be obtained from the NYC Department of Finance before filing.

Why a Knowledgeable Expediter Makes All the Difference

Even with well-prepared drawings, the success of your filing often depends on your ability to work the system—accurately and efficiently. A skilled expediter will collaborate with your architect to:

• Catch DOB red flags before submission
• File Alteration GC and PL applications with proper scope
• Navigate plan examiner objections
• Manage inspections and help obtain the Letter of Completion without delays

Combining apartments in NYC is more than just a renovation—it’s a regulatory puzzle that demands experience and precision.

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