Specialty Shape Window Types
Most shaped windows don't open. Leaving out the sash is what makes the odd geometry affordable to build, and fixed glass has fewer places to leak air. The exceptions are some operable transoms and arched-top units with a working window under the curve.
Arched and Half-Round Windows
Radius windows cover a family of curves. A half-round (half circle) sits on top of a rectangular window. A quarter-round fits a corner of a gable. An eyebrow is a shallow arch. A springline window has square bottom corners and straight sides that curve into a round top. The most common use is a half-round transom over a double-hung or a picture window, matching the sight lines of the window below.
When you replace an old arch, measure the replacement as its own unit. Custom sizes are common in older homes with non-standard openings, so don't assume a catalog arch will drop in. Ask the installer to template the curve if there's any doubt.
Transom Windows
A transom is any window that sits above a door or another window, on top of the horizontal framing member called a transom. Rectangular ones are the most common; semicircular ones over doors are called fanlights. Most modern transoms are fixed and decorative, though some open on bottom hinges. On an exterior door, This Old House advises ordering the door, transom and sidelights as one sealed unit rather than adding glass over an old door. For transoms above large fixed panes, see picture windows.
Round and Oval Windows
A circle or oval window is usually an accent: high in a gable, at a stair landing or over a tub. It's fixed glass, so there's nothing to maintain beyond the seal. A round window sitting in a field of siding has a continuous curved edge to flash, and that's the detail to ask about. If the siding under an old circle window is stained or soft, expect some carpentry with the replacement.
Octagon Windows
An octagon is a common pick for a stair landing or a powder room. In our view it's easier to frame and flash than a true circle, because every side is straight. Obscure glass makes it a good choice in a bathroom, and an octagon set low beside a tub falls under the bathroom rule on the tempered glass windows page.
Trapezoid and Gable-End Windows
Trapezoids and triangles follow the slope of a roof. They show up above a row of picture windows in a cathedral-ceiling living room or in the gable of a porch. They're usually joined to the rectangular windows below to make one large unit, so they're replaced with that unit in mind.
Why Troy homeowners call Troy Windows
- Free in-home measure of every opening
- Written, itemized quote before any work
- Frames and sills checked before a price
- One local window installer, not a call list
- No charge to homeowners for the referral
Specialty Shape Window Cost in Troy
Shaped windows are custom work, so the national averages below are rough guides.
| Window | National price | Source |
|---|---|---|
| Transom | $200 to $700 per window | Fixr, 2026 |
| Transom, installed | $825 to $2,500, about $1,730 average | This Old House research |
| Custom or non-standard window | $1,000 and up | Fixr, 2026 |
HomeGuide notes that arched, round and custom shapes cost more to make than a standard rectangle of the same size. Fixr adds that custom sizes, common in older homes with non-standard openings, push material costs up. A half-round above a stock window costs much less than a large trapezoid joined to a wall of glass.
Specialty Shape Windows in Troy: Installation and Code Notes
Installation Takes Longer
One large window maker says shaped windows take longer to install than rectangles, because framing needs more angle cuts and miters and flashing is harder. Flashing has to be shingled: start at the bottom and lap each higher layer over the one below. That's the step to ask about, because a leak over a curved head shows up as stained drywall years later. If water already gets in around an old shape, see window leak repair.
Matching the Windows Below
A shaped transom should match the frame color, material and grille pattern of the window under it. If you're replacing the main windows now and the arch later, order them from the same series so the profiles line up.
Permits for New Shapes
Adding a shape where there was none means cutting framing, so ask whether the quote includes the permit. Shaped units carry NFRC ratings like any other window, so read their labels the same way (energy efficient windows).