Professional specifications, installation guide & design solutions
A transom window is the lite above a door or a window, separated by a horizontal bar — the transom. It brings light over an entrance, a vestibule or an interior door, and on brownstones and townhouses it is often the leaded or stained glass panel that survives from the original house. We supply fixed, awning and pivot transoms in every system we fabricate, restore and protect original glass transoms, and match new transoms to landmark originals.
We carry multiple premium manufacturers for transom-window windows including:
Each brand offers distinct advantages in performance, design, and price point. We can help you choose the perfect fit for your project.
Proper installation is critical for optimal performance. Our installation team provides:
Installation includes sealing and flashing the perimeter of the opening, because a window is only as watertight as the junction between it and the building. Where an opening needs more than that — a failed sill, damaged masonry, a detail that was wrong to begin with — see waterproofing.
A transom is a window above another opening — above a door, above a storefront, above a window. It is one of the oldest pieces of building sense there is, and it does three things at once.
It brings daylight deeper into a room. Light entering high travels further across a ceiling than light entering at eye level. In a deep brownstone room, or a hallway with a single elevation, a transom is often the difference between a usable space and a dark one.
It ventilates at high level. Warm air collects at the ceiling. An opening transom lets it out, and in the days before air conditioning that was why every apartment door in New York had one above it.
It gives light without giving privacy away. A transom above a door lights a hallway without anyone being able to see through it from standing height.
Most modern transoms are fixed, which is a missed opportunity where the room would benefit from stack ventilation.
Where a transom does open, an awning is the usual arrangement — hinged at the top, opening outward at the bottom, so it forms a canopy over its own opening and can stay open in rain. A hopper is the inward equivalent.
Reach is the practical problem: a transom is by definition out of arm's reach. A chain operator or an electric operator solves it, and on a stairwell or double-height space an electric operator is usually the only workable answer.
Safety glazing is required in panels adjacent to doors, and a transom directly above a door generally falls within that. Tempered or laminated, not ordinary annealed glass.
Ventilation area. Where a transom is contributing to the openable area required for a habitable room, only the part that actually opens counts — a fixed transom contributes nothing to the ventilation calculation, however much light it brings in.
Over a circulation route. Anything above a walkway or a corridor should be laminated, so that a failure does not drop glass on people below.
New York's older housing stock is full of them: fanlights over brownstone entrances, leaded and stained transoms in pre-war apartment buildings, the hinged glass panels above apartment doors that are now almost always painted shut.
These are frequently original, frequently single glazed, and frequently in a historic district where the profile and the glazing pattern are governed by the approval. A conventional insulating unit will not fit an original transom rebate. Where performance is needed inside an approved historic profile, vacuum glazing at around 8mm is usually the only route.
Where an original leaded or stained transom survives, restoring it is normally a better outcome than replacing it, and on a landmarked frontage it may be the only permitted one.
These describe the kind of work each area brings rather than any specific client project.
Brownstone and rowhouse entrances — Park Slope, Carroll Gardens, Bed-Stuy, Harlem. Fanlights and entrance transoms, usually landmarked, usually original. Restoration or careful replacement to an approved profile.
Pre-war apartment interiors — upper Manhattan, the Bronx, central Brooklyn. Over-door transoms, mostly painted shut. Freeing and repairing them is a cheap improvement to a dark interior hallway.
Storefronts — Flatbush, Coney Island Avenue, Fifth Avenue Park Slope. Traditional shopfronts have a transom band above the display window, and on a landmarked frontage it is part of what the review expects to see.
Stairwells and double-height space — townhouses and loft conversions citywide. High-level ventilation with electric operation, where nothing else is reachable.
Tell us the opening size, whether the transom should open, and whether the building is in a historic district. We supply and install across Manhattan, Brooklyn, Queens, the Bronx and Staten Island, and throughout Northern New Jersey, the Jersey Shore, Philadelphia and the Lehigh Valley.
A transom window is a window set above a door or another window, separated from it by a horizontal bar called the transom. It can be fixed or operable, rectangular, segmental or a half-round fanlight, and it exists to bring light — and, when it opens, air — over an opening that the door or lower window cannot.
| Type | Where you see it | Notes |
|---|---|---|
| Fixed rectangular transom | Over entry doors, storefront doors, interior doors | The most common; glass is usually tempered because it is within 24″ of a door |
| Operable transom (awning or hopper) | Pre-war apartments over interior doors; some storefronts | Opens for ventilation; the historic operator was a rod or chain; modern versions use a crank |
| Fanlight (half-round or elliptical) | Brownstone and Federal entrances, Georgian houses | Radial muntins from the centre; the arch is fixed. See arched windows |
| Segmental or arched transom over a window | Brick rowhouses | Head follows the brick arch; usually a fixed lite mulled to the window below |
| Storefront transom | Retail fronts, restaurants | Continuous band above the display glass and doors; often houses signage, louvres or lighting |
| Sidelite-and-transom set | Entry systems | Transom spans door and sidelites in one frame |
Any transom within 24 inches of a door edge is a hazardous location under the Building Code and takes safety glazing — tempered or laminated. Transoms over storefront doors are usually 1/4″ tempered or a 1″ insulated unit matching the storefront; residential transoms match the window below. Operable transoms get hinged hardware and a limiter where a child could reach them; on a fire-rated corridor door the transom must carry the same rating as the door, which means fire-rated glass and a listed frame.
Historic operable transoms in pre-war buildings are worth keeping: the sash, the pivot and the rod operator are simple, and a repaired transom with new glass and weatherstripping is often better than a replacement. Where the building is landmarked, the LPC will expect the transom pattern kept on the street facade.
On a commercial front the transom band is where the design problems live: signage, the door closer, HVAC louvres and lighting all want the same strip. On 300 East 50th Street the louvres are built into the transom over the entrance; on Grand Prix Custom the commercial door carries a transom in the same black frame. We draw the transom as part of the storefront, not as an afterthought, so the sightlines line up across the whole front.
There is no single standard size for a transom. The width is set by what is underneath it: a transom is normally the same width as the door or window frame below, or it runs across the door and its sidelites as one band. The height is whatever is left between the top of the door and the head of the opening, which is why transoms range from a narrow strip to a tall lite.
| Where | Typical width | Typical height |
|---|---|---|
| Over an interior door | Same as the door frame: about 30″ to 36″ | 8″ to 16″ |
| Over a single entry door | About 36″ to 42″, or wider to span sidelites | 10″ to 24″ |
| Over double or French doors | About 60″ to 72″ | 12″ to 24″ |
| Over a window | Same as the window below | 12″ to 24″ |
| Storefront transom over a 7′-0″ door | Same as the door or the full bay | 12″ to 36″ and more, set by the opening height |
These are the ranges we see most often, not catalogue sizes. Two things decide the real dimension. First, door height: with an 80-inch door under an 8-foot ceiling there is room for only a low transom, while a 9- or 10-foot ceiling allows 18 to 24 inches. Second, proportion: a transom usually looks right at roughly a quarter to a third of the door height, and its glass sightlines should line up with the door stiles below. On replacement work in old buildings the masonry opening decides, so the transom is measured and made to fit.
There is no single standard. A transom is normally as wide as the door or window below it and roughly 8 to 24 inches high in houses and apartments; storefront transoms over a 7-foot door are often 1 to 3 feet high. The opening height decides.
Usually a quarter to a third of the height of the door below, which is about 12 to 24 inches over a standard door when the ceiling height allows it.
A window above a door or another window, separated by a horizontal bar called the transom. It can be fixed or operable, rectangular or arched, and it exists to bring light and air over an opening.
If it is within 24 inches of a door edge, yes — the Building Code treats it as a hazardous location and requires safety glazing, tempered or laminated. Transoms over storefront doors are almost always tempered.
Yes. Operable transoms hinge as awning or hopper sashes and were standard over interior doors in pre-war apartments for ventilation. We repair the originals or supply new operable transoms with crank or rod operators.
A half-round or elliptical transom over an entrance, usually with radial muntins, typical of Federal and Georgian houses and brownstone entrances. It is a fixed arched transom; see our arched windows page.
Yes. We survey the existing transom and muntin pattern, draw the replacement to match and prepare the LPC submission; on street facades the pattern is generally required to be kept.
They should share the framing system and sightlines. We design the transom band with the door, signage, louvres and lighting in mind so the front reads as one.
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