Fixed windows made to a shape — round, oval, octagon, hexagon, pentagon, triangle, rake, round-cornered and peaked — templated on site and made in aluminium, wood-clad or steel to match the windows around them. Supplied and installed across NYC, Long Island and New Jersey.
A shaped window is a fixed window made to a geometry other than a rectangle: a circle in a gable, an octagon on a stair, a triangle under a roofline, a trapezoid following a rake, a quarter round beside a door. They are almost always fixed — the point of the shape is the shape, not ventilation — and they are templated, fabricated and glazed to the opening rather than picked from a size chart. We supply and install them in aluminium, wood-clad and steel, in the same finishes and glass as the rectangular windows around them, so a shaped unit matches the elevation instead of announcing itself.
| Shape | What it is | Typical use |
|---|---|---|
| Full circle | A fixed round window, often with radial or cross muntins | Gable ends, stair halls, above a front door |
| Ellipse / oval | A curve with two radii, wider than tall or taller than wide | Colonial Revival gables, powder rooms, feature walls |
| Half round and quarter round | A semicircle or a single quadrant, usually over or beside another unit | Transoms, stair windows, corners of a bay |
| Octagon and hexagon | Regular polygons with straight sides | Attic and bathroom windows, stair landings, Queen Anne detail |
| Pentagon | Five sides, usually a rectangle with a peaked top | Gable ends under a pitched roof |
| Triangle | Equilateral, isosceles, or right-angled left or right | Under a roofline beside a rectangular window; A-frame and contemporary houses |
| Trapezoid / rake | A rectangle with one raked side following a roof slope | Cathedral ceilings, dormers, clerestories |
| Round corners | A rectangle with radiused corners | Art Deco and Streamline Moderne buildings, some industrial lofts |
| Peak / cathedral | A rectangle rising to a point | Church and chapel windows, contemporary gables |
Straight-sided shapes — triangles, trapezoids, polygons — are cut and joined at the corners like a rectangle, just at angles other than ninety degrees. Curved shapes are roll-bent from the same profiles, which gives a true curve with a consistent section. The insulated glass is cut to the template; polygons and curves both get curved- or angle-cut sealed units as standard, so a shaped window carries the same low-E and argon as the rest of the house. Grids, between-the-glass or applied, can follow the geometry: radial on a circle, a cross on an octagon.
For the openings that combine a shape with a standard window — a peak over a picture window, a quarter round beside a door — the shape is made with an extended leg so its frame meets the unit below on one line, or the two are mulled in the shop and installed as one. Crystal’s CAP 280/380/480 series lists every one of its twenty-four geometries with an extended-leg version for this reason.
Shaped openings are the ones where the drawings are least likely to match the wall. A gable triangle is only as true as the rafters; a circle cut in brick has a few high bricks; an octagon built by a carpenter forty years ago is close to regular but not regular. We template on site, record the governing dimensions (for a circle, the diameter in two directions; for a polygon, each side; for a rake, the angle and the height at both ends) and fabricate to the template. It adds a visit and removes the risk of a window that almost fits.
Most shaped-window work is replacement: the original wood octagon has rotted, the aluminium circle from the 1980s has a failed seal, the triangle under the eaves was never double-glazed. The replacement matches the outside geometry and usually improves what is inside it — a thermally broken frame, a proper insulated unit, a finish that matches the new windows elsewhere on the house. Where the house is in a historic district, the shape is one of the things the Landmarks Preservation Commission expects to see kept.
Half rounds, segmental, eyebrow and gothic heads are a family of their own, with their own geometry and their own place in New York’s brick and brownstone streets. They have their own page: arched windows.
Almost never; shaped windows are fixed. Ventilation in a room with a shaped window comes from an operable unit beside or below it. A few manufacturers offer operable octagons and half rounds in wood, but they are rare and we generally advise against them.
Circles, ellipses, half and quarter rounds, octagons, hexagons, pentagons, triangles of every kind, trapezoids and rakes, round-cornered rectangles, peaks and cathedral tops, and arches. Crystal alone lists twenty-four standard geometries; other shapes are made to the template.
Yes. The insulated glass unit is cut and sealed to the shape, so a shaped window has the same low-E, argon-filled glass as a rectangular one.
More than a rectangle of the same area because of the site template, the shop drawing and the shaped glass; polygons cost less than curves, and a shape that repeats across a facade costs less per unit than a single one. We quote from the template rather than a price list.
That is the point of ordering it from the same system: the same finish, the same glass, and grids that follow the geometry. We supply the shape and the rectangular windows from one manufacturer so the elevation reads as one set.
Yes, and it is most of the shaped-window work we do: template the opening, match the outside geometry, and fit a thermally broken frame with an insulated unit inside it.
Arched Windows Fixed Windows Crystal Architectural Shape Windows Transom Windows Landmark Window Replacement Window Replacement in NYC Glazing Glossary
About this page. Written by Alex GC Inc. d/b/a Alex Glass Construction and reviewed before publication by Aleksandr Chernovolenko, Managing Partner, with our design and estimating lead and a field foreman. Our foremen hold the NYC DOB Site Safety Training supervisor card and our crews the 40-hour worker card; we are certified to fabricate, install and service Alutech and Everest aluminum systems. Facts are drawn from our own projects, manufacturer test data and the applicable codes; where we are giving an opinion, we say so. Last reviewed September 2026. Credentials
Send a photograph and rough dimensions of the opening and the windows near it. We will template it, match the system and finish to the rest of the house, and quote the shape and any window it joins as one unit.
