Historic Window Restoration
Window Restoration in New York City
Wood sash, steel casement, stained glass and leaded panels — restored to the standard the Landmarks Preservation Commission expects, across all five boroughs. LPC-approved, EPA Lead-Safe certified, 17+ years, 80+ heritage sites.
What we restore
New York’s historic windows were never built as sealed units. They were built as assemblies of parts — sash, stiles, rails, muntins, glazing putty, pulleys, cords, counterweights, blind stops, parting beads — and an assembly of parts can be taken apart and put back together. That single fact is what makes restoration possible on windows a replacement contractor will tell you are finished.
We work on four families of historic glazing, all of them in-house:
- Wood double-hung sash — the workhorse of the brownstone, the rowhouse and the pre-war apartment house. Two-over-two, one-over-one, six-over-six, and the tall parlour-floor units that set the rhythm of a whole facade.
- Steel and bronze casement — Art Deco apartment houses, garden-apartment complexes and cast-iron loft buildings, where slender steel sections carry a glass area no thermally-broken aluminium replacement can imitate.
- Stained and leaded glass — transoms, stair-hall windows, heraldic panels and cathedral figurative work, releaded and re-set by hand.
- Dalle de verre — mid-century faceted slab glass set in a concrete or epoxy matrix, a material almost nobody in the city still services.
Alongside the glazing itself we carry out EPA Lead-Safe certified lead paint stabilisation and abatement on historic sash and frames, because on any pre-1978 building that work is part of the window job whether or not anyone budgeted for it.
How we assess a window
Every project starts with a free on-site assessment, and the assessment is done window by window rather than building by building. A facade is not one condition; it is twenty or two hundred separate conditions that happen to share an address.
We open each sash if it still opens. We probe the bottom rail, the sill horns, the lower stiles and the joints where rail meets stile — the places water sits and rot starts. We check whether the weight pockets are intact and whether the cords have been cut. We record the sash thickness, the meeting-rail profile, the muntin width, and the depth of the sash within the opening measured from the plane of the facade, because those are precisely the dimensions Landmarks will ask for if the work needs a permit.
Then every opening gets a tag and a scope — refurbish or replace — and that per-unit record becomes two things at once: your scope of work, and the backbone of the LPC filing. It is also what stops a project turning into a change-order argument in month three, because the condition of each unit was written down before anyone ordered anything.
Landmarks recommends inspecting historic windows every five to seven years. Most of the buildings we are called to have not been looked at properly in thirty.
Restore vs. replace: how the call gets made
Condition decides. Not preference, and not a sales position — HM does both disciplines to the same standard, and on most buildings we end up doing both on the same facade.
A window goes to restoration when the frame is sound and the sash can be rebuilt: localised rot that can be cut out and consolidated, failed putty, broken cords, seized pulleys, paint build-up choking the profiles, glass that can be saved or matched. This is the outcome Landmarks generally prefers, because it keeps the original material, the original glass and the original profiles that give the building its character.
A window goes to replacement when the original is genuinely beyond saving — structural loss through the joinery, a frame rotted into the masonry pocket, a unit already replaced badly in the 1970s with nothing historic left to conserve. In that case we specify a landmark-grade replacement built to match the historic design, from Marvin, Norwood or Caoba, matching material, operation, configuration, details and finish.
What we will not do is tell you that one route is automatically the cheaper one. Cost turns on the condition of the individual unit, how much hand work it needs, and — on the replacement side — which manufacturer and which line the approved design calls for. Two windows in the same building, ten feet apart, can honestly land on opposite sides of that call.
Materials and methods
The methodology is conservation practice, not carpentry improvisation, and it runs in a fixed sequence in our Newark workshop:
- Paint removal — controlled stripping back to sound substrate under lead-safe containment, recovering the crisp profile that thirty coats of paint have buried.
- Epoxy consolidation — decayed but original wood stabilised in place rather than cut away, so the maximum amount of historic fabric survives.
- Dutchman repair — where loss is too great to consolidate, a shaped patch of matching species let into the sound wood and worked flush, instead of scrapping the member.
- Reglazing — historic glass retained wherever it survives, bedded and back-puttied properly; where a pane is gone we match the period glass rather than dropping in modern float.
- Mechanism rebuild — pulleys freed or replaced in kind, cords or chains renewed, counterweights re-hung and rebalanced to the actual weight of the restored sash.
- Weatherisation — integral weatherstripping fitted into the sash and frame, tightening the assembly without altering the sightlines or the plane of the window.
- Reinstallation and repaint — refitted on site by factory-trained, lead-safe crews, finished in the approved colour, with closeout documentation for your records.
On leaded and stained work the sequence is different — documentation, rubbings, controlled disassembly, releading, and reinstatement with protective glazing where exposure justifies it. That work is covered in detail on our stained glass and leaded window restoration page.
The LPC process, managed
If your building is an individual New York City landmark or sits inside a designated historic district, most exterior window work needs a Landmarks permit before it can start — including work on elevations nobody can see from the street. Full window replacement is explicitly not treated as minor maintenance.
We manage that end to end: existing-conditions documentation and photography, drawings and material specifications, the filing itself through LPC’s Portico portal, and direct liaison with Landmarks staff through to approval and final sign-off. Around 95% of Landmarks approvals are granted at staff level rather than at a public hearing, and getting into that lane is mostly a function of how the application is built.
The permit types, the five attributes Landmarks tests every window against, and realistic timelines are set out on our guide to LPC window approval in NYC.
Where we work
All five boroughs, from our workshop in Newark, New Jersey — plus nearby New Jersey. Our portfolio includes more than 70 windows at The Dorilton, one of Manhattan’s most ornate Beaux-Arts landmarks, and the re-creation of curved glass for a Brooklyn Heights brownstone.
Common Questions
Questions we get asked on this work
How much of a historic window can actually be saved?
More than most owners are told. Because a historic sash is an assembly of separate members, decay is usually confined to the bottom rail, the lower stiles and the joints where they meet — the places water sits. Those members can be consolidated with epoxy or repaired with a shaped Dutchman patch of matching species, leaving the rest of the original sash, and usually the original glass, in place. Whole-unit replacement is the answer when there has been structural loss through the joinery or the frame has rotted into the masonry pocket.
Do you restore steel casement windows as well as wood?
Yes. Steel and bronze casements are a core part of the work, particularly in Art Deco apartment houses, garden-apartment complexes and cast-iron loft buildings. Slender steel sections carry a glass area that thermally-broken aluminium replacements cannot imitate, which is exactly why Landmarks resists losing them.
Will restored windows still be draughty?
Not if the mechanism and the weatherisation are done properly. Most of the air leakage in an old double-hung comes from a loose sash in a distorted frame, failed glazing putty and missing weatherstripping — all three of which are addressed in the restoration sequence. Integral weatherstripping is fitted into the sash and frame, so the assembly tightens without changing the sightlines or the plane of the window.
Can you work while the building stays occupied?
Yes, and most of our work is done that way. Sash are removed, rebuilt in the Newark workshop and refitted, which keeps the disruptive work off site. On any building constructed before 1978 the work is carried out under EPA Lead-Safe certified containment, because disturbing historic paint triggers federal RRP and NYC lead-safety requirements.
Do you work with architects and property managers, or only owners?
Both. We partner with architects, designers, property managers, co-op and condo boards, general contractors and individual owners — coordinating drawings, specifications and Landmarks submissions so the window scope fits into the wider project rather than fighting it.
Free Assessment
Get a free on-site assessment.
We visit your building, inspect the windows one by one, discuss any board or Landmarks requirements, and walk you through the options — restoration, replacement and approvals. No cost, no obligation.