LPC Window Approval in NYC: How the Permit Process Actually Works

If your building is an individual New York City landmark or stands within a designated historic district, almost any exterior window work needs an LPC permit before it starts — including work on elevations that cannot be seen from the street.

Landmarks jurisdiction covers restoration, in-kind replacement, alteration, reconstruction, demolition and new construction affecting the exterior of a designated building. The "nobody can see it" argument does not work: the rules apply to non-visible facades too, they simply apply less strictly, which is a different thing.

Full window and door replacement is explicitly not treated as minor maintenance. Neither is a full restoration methodology — stripping, reglazing and repainting a whole sash needs a permit even though every individual step sounds like maintenance.

Work that genuinely does not need a permit is narrower than owners expect: replacing broken glass or hardware in kind, replacing caulk in kind, replacing gutters and leaders in kind, repainting or touching up in the same colour, low-pressure water washing, temporary boarding, removing an already-dislodged element and tarping storm damage. Note the trap — repainting in the same colour is fine; a colour change needs a permit.

If your scope is anywhere near that line, confirm it rather than assume. Doing designated-building work without a permit is a considerably worse problem than filing for one you did not strictly need.

Five attributes decide everything: material, operation, configuration, details and finish — and how strictly each must match the historic window depends on which facade it is on and how big the building is.

Primary facade — the street-fronting elevation, or any equally significant visible one. Configuration, details and finish must match the historic window. Operation generally must match, with named exceptions. Material must match for individual landmarks and for small buildings — defined as six storeys or fewer and under 40 feet of frontage — except that small buildings historically fitted with one-over-one wood double-hungs may change material, though never to vinyl. Large buildings — seven storeys or more, or 40 feet or more of frontage — may use a different material. Glazing diminution, meaning how much daylight opening you lose to thicker sections, is capped at 6% for wood and 10% for metal.

Visible secondary facade — configuration and finish must match; the window may shift within the opening, and the opening itself may be modified if the general shape and pattern are retained or a new regular pattern results.

Non-visible secondary facade — no match required at all. This is where the real flexibility lives, and it is worth knowing that Landmarks has a working definition of "minimally visible": an opening seen at such an angle that its configuration cannot be recognised, or where only a small portion of the facade is visible.

Special windows — rare or distinctive glazing such as stained glass — must match on all five attributes on every facade, visible or not, and require a condition assessment.

There are useful named exceptions at primary facades. The upper sash of a double-hung or a transom may become fixed even if it was historically operable. Casement, awning and hopper swing direction may change. A pivot window may become hinged if the orientation is preserved — but not at an individual landmark. Simulated divided lights may substitute for true divided lights where the muntins match in material, are permanently affixed, and the spacer bars replicate the true-divided-light appearance. And in historic districts only, high-performance "passive house" simulated double-hungs are acceptable for a building-wide efficiency retrofit — but every primary-facade window except special windows has to be replaced at the same time. There is no piecemeal version.

A complete staff-level application is in the region of ten business days; an expedited interior CNE about five; a Certificate of Appropriateness requiring a public hearing runs weeks to months. The variable that actually determines your schedule is how complete the package is when it goes in.

Ten business days is the review clock, not the project clock. Build the real programme backwards from these:

• Survey and documentation — the existing-conditions record, photography and per-window dimensions. This is where the calendar time goes, and rushing it is what causes the rest to slip.
• Drawings and specifications — elevations, sections and details, plus manufacturer specifications where units are being replaced.
• Staff review — around ten business days for a complete PMW or CNE. An incomplete filing does not get refused so much as it gets queried, and each round of queries restarts your waiting.
• Public hearing, only if you get there — weeks to months, and a Status Update Letter from the Commission before the COFA is issued.
• Fabrication — after approval, not before. Landmark-grade replacement units are made to order.

Two things worth planning around. Once issued, a Permit for Minor Work runs for years rather than months — a PMW issued in February 2026 on one of our Brooklyn filings expires in 2030 — so approval does not force you to start immediately. And if you own a larger building facing phased work, LPC allows a one-time master plan for window and door replacement across units over time, with no expiration date; once it is approved, individual unit filings under it move considerably faster than filing each one from scratch.