NYC's window approval maze: LPC, DOB, and your co-op board—What's actually required

There is no city in the country where replacing a window is more complicated than New York City.

The source of the confusion: there isn't just one approval process for NYC windows. There are up to three, depending on what kind of building you're in and what you're doing to it: The Landmarks Preservation Commission (LPC). The Department of Buildings (DOB). Your co-op or condo board. Each has its own jurisdiction, its own requirements, and its own timeline (and they don't necessarily coordinate with each other).

"Most homeowners have never replaced their windows before," said Kyle Perdelwitz, General Manager of Window & Door Pro, a New York City window and door installation company with more than 20 years of experience helping homeowners, co-op shareholders, and building managers navigate the city's complex approval landscape. "Windows are a considerable investment, and most don't fully understand the costs and approval processes involved in a window replacement project." 

This guide maps out which approval matters for which situation so you know what you're walking into before the process starts.

Which approvals apply to your property?

Use this chart as a starting point, as your specific building may have additional requirements. When in doubt, check with your managing agent or installer before specifying any product.

✓ Required = this approval is typically mandatory
May apply = depends on building specifics
— = generally not applicable

The Landmarks Preservation Commission (LPC)

The LPC is the city agency responsible for protecting New York's historic buildings and neighborhoods. It has jurisdiction over more than 36,000 individually landmarked properties and 150+ historic districts across the five boroughs. If your building or your block falls into either category, the LPC has authority over any change to the exterior appearance of your property, which includes windows.

This surprises many homeowners, particularly in brownstone Brooklyn. You can own your building outright, pay your own bills, and still need a city commission to sign off before you touch your windows. That's because in a historic district, the facade is considered part of the neighborhood's shared visual character—not just your personal property.

What the LPC actually reviews

The LPC isn't trying to freeze your building in time. They're trying to ensure that replacement windows maintain the visual character of the original (what the commission calls "in-kind replacement"). In practice, that means evaluating:

• Profile and dimensions: the physical size and shape of the frame as seen from the street
• Sight lines: the visible lines created by the frame, sash, and any muntins (the dividers between panes)
• Glass-to-frame ratio: how much of the opening is glass versus frame
• Operability: how the window opens (double-hung, casement, etc.)
• Material: not always restricted, but must achieve the same visual result as the original

Notably, the LPC does not require you to use the exact same material as the original window. Wood-clad, aluminum, or fiberglass can all be approved if they replicate the visual characteristics. What gets rejected is a modern aluminum slider going into an opening that had a traditional double-hung, or a vinyl frame that reads visually heavier than the original. 

Historic district vs. individual landmark

It's worth distinguishing between two situations that both involve the LPC but work differently in practice.
Properties in a historic district—like Brooklyn Heights, the Greenwich Village Historic District, or Harlem's St. Nicholas Historic District—follow LPC guidelines for the neighborhood as a whole. Simple in-kind window replacements in historic districts can sometimes be approved at the staff level, meaning you may not need to appear before the full commission. This is faster, but it still requires documentation and still requires an LPC-approved product.

Individually landmarked buildings face more stringent review. These are specific properties designated for their architectural or historical significance (think the Dakota on the Upper West Side or any of the historic rowhouses on Remsen Street in Brooklyn Heights). Work on these buildings requires a full LPC submission with architectural drawings, and changes are more closely scrutinized than in a standard historic district review.

Practical note: Not sure if you're in a historic district or landmarked building? Check the NYC LPC's online map at nyc.gov/landmarks or simply ask your window contractor.

The Department of Buildings (DOB)

The Department of Buildings is the agency responsible for ensuring construction in New York City complies with the building code. For window replacements, DOB permits are required more often than most homeowners expect—and the consequences of skipping one can include fines and an order to remove the work.

When is a DOB permit required for windows?

As a general rule, a DOB permit is required when window replacement involves any of the following:

• Changing the size or location of the window opening
• Structural work to the surrounding wall or lintel
• Changes to a fire escape egress window
• Full building envelope work (e.g., building-wide replacement programs)
• Any work on a landmarked building (LPC approval must come first)

A straight in-kind replacement (same size, same location, no structural changes) may not require a DOB permit in all cases. But the determination is building-specific and depends on factors including whether the building is a one- or two-family dwelling versus a larger residential building, and what's in your co-op's alteration agreement.

"Anything structural will need a permit—anything where openings are being enlarged or headers are being replaced," Perdelwitz said. "In-kind replacements are often grandfathered in, but if you're creating a new opening, you're left to comply with modern codes. The DOB enforces building standards and codes; the LPC puts back what the Landmarks Commission deemed period-specific." 

Important: When both LPC and DOB approval are required, the LPC must sign off first. DOB will not accept a filing for landmarked work without an LPC Certificate of Appropriateness. Getting this sequence wrong can add significant time to a project.

Who files the DOB permit?

For most residential window projects, the contractor handles the DOB filing—it's part of what you're paying for when you hire an experienced NYC window installer. If a contractor tells you permits aren't necessary for work that clearly requires them, treat that as a serious warning sign. Unpermitted work can complicate a future sale, trigger fines, and in some cases require the work to be undone.

Caption

Window & Door Pro installed new double-hung windows on this brownstone, matching the original profile and sight lines - the kind of in-kind replacement LPC review is built around.

Credit

Window and Door Pro

Your co-op or condo board

For the majority of New York City homeowners (who live in co-ops and condos rather than freestanding buildings) the board is the first and most immediate approval they'll need. And in some ways it's the most unpredictable, because every building runs its own process.

Co-ops: Expect stricter oversight

Co-op buildings are structured as corporations. You don't own your apartment outright—you own shares in the corporation and hold a proprietary lease. That structure gives the board significant authority over what happens inside and outside your unit, including windows.

Most co-op boards require prior written approval for any window replacement. Beyond that, many boards have gone further: they've standardized the window product for the building, designating a specific manufacturer or style to maintain a uniform facade. If you're in one of those buildings, the choice isn't really yours—you're selecting from an approved list, and anything outside that list requires a variance that the board may or may not grant.

"The smoothest projects are the ones with constant communication and clear direction," Perdelwitz said. "Make sure you're including all necessary parties—the board, the superintendent, the managing agent—in the conversation, and then follow the building's unique approval process. Asking for forgiveness rarely results in happy stakeholders."

Even if your building hasn't standardized on a specific product, the board can still reject your plans if the proposed window would create a facade mismatch—a different profile, finish color, or visual character from what's in place on the rest of the building. The goal, from the board's perspective, is that the building looks intentional and maintained, not like a patchwork of 40 different window replacements done over three decades.

Condos: Usually more flexibility, but not always

Condo owners hold title to their units and have more autonomy than co-op shareholders. But that doesn't mean the approval process disappears. Most condos require notification and sign-off for exterior changes—windows included—and buildings with strong common charge structures often have architectural review processes that look similar to a co-op's.

The key distinction is that condo boards generally have less power to mandate specific products. They can enforce aesthetic standards (the windows need to match the building's existing character), but they typically can't require you to use a specific manufacturer the way a co-op can.

What to ask before you start

Before specifying any product for a co-op or condo window replacement, get answers to these questions from your managing agent:

• Does the building have an approved manufacturer list for window replacements?
• Is there a required window style, profile, or finish color for the facade?
• Does the alteration agreement cover window replacements, and if so, what does it require?
• Is there a timeline for board review and approval (some buildings have monthly board meetings that gate the process)?
• Are there preferred or required contractors for window work?

When all three apply

The most complex window replacement situation in New York City is also one of the most common in certain neighborhoods: a co-op apartment in an individually landmarked building or a building within a historic district. Think prewar doorman buildings on the Upper West Side or Upper East Side, or a converted historic building in a named Brooklyn historic district.

In this scenario, you're navigating:

• Your co-op board's approval process and any product standards they've established
• LPC review for the exterior change, requiring architectural documentation and compliance with in-kind replacement standards
• DOB permit filing, which cannot be submitted until the LPC Certificate of Appropriateness is in hand

The sequencing matters. LPC first. Then DOB. The board can run concurrently with LPC, but practically speaking, you'll want board approval lined up before you invest in LPC documentation—because if the board rejects your plans, the LPC work is wasted.

"Each project has its own outside variables," Perdelwitz explained. "If there's uncertainty about what's needed, or if the drawings leave out key details, it will derail and extend the project timeline. A clean drawing, filed properly, will often take three to four months, but multiple factors can speed things up or slow them to a halt." 

The right sequence: Board approval (or at minimum board alignment) → LPC submission → LPC Certificate of Appropriateness → DOB permit filing → installation. Skipping steps or doing them out of order is the primary reason projects stall.

The one thing that makes all of this easier

Navigating three different approval bodies, each with their own requirements, timelines, and documentation standards, is a lot. But the homeowners who find this process manageable share one thing: they hired someone who had done it before.

An experienced NYC window contractor isn't just there to handle the physical installation. They know which approvals your project requires before you ask, they prepare LPC documentation correctly the first time, they handle DOB filings without you chasing them down, and they know which products will pass a co-op board review and which ones won't.

Window & Door Pro has managed the full approval process —LPC, DOB, co-op boards—across hundreds of projects in New York City over more than 20 years. Their process starts with a property assessment before any product is specified, precisely because the approval landscape shapes everything else.

If you're planning a window or door project and aren't sure where your approvals stand, that first conversation is the right place to start.