Arch Window

Arched Windows: Why They Cost More

An arched window is not a rectangular window with a curved top. Almost everything about making one is different, and understanding why explains the price.

The Shapes

Full round is a complete circle. Half round is a true semicircle, where the radius equals half the width. Segmental is a shallow arc struck from a much larger radius — by far the most common on New York rowhouses, and frequently mistaken for half round on a drawing. Elliptical is a true ellipse rather than an arc, which cannot be drawn with a single compass point. Gothic comes to a point. Eyebrow is a very shallow, flattened curve. Quarter round and extended arch variants sit above straight sides.

Getting the geometry right is the first problem. A segmental arch and a half round look similar in a photograph and are completely different to fabricate, and a unit made to the wrong geometry does not fit at all — there is no adjusting it.

Why We Template Rather Than Measure

A rectangular opening is described by two numbers. An arched opening is not describable by numbers at all unless it happens to be a perfect arc, and in a building a century old it almost never is. The masonry has moved, the two springing points are rarely level, and the curve is frequently not symmetrical.

So we make a physical template of the actual opening and fabricate to it. It takes a visit and it is the difference between a unit that fits and one that is scrap. Anyone quoting an arched window from dimensions alone is guessing.

Glass and Frames

Glass for a curved head is cut to the template. Where the head itself is curved in plan as well — a bow or a genuinely curved facade — the glass has to be slumped to shape, which is a specialist process with its own lead time and cost. Faceted alternatives, using several flat panes to approximate a curve, are sometimes the sensible answer and we will say when.

Frames are either bent to the radius or built up from segments and machined. Either way the labour is considerable compared to cutting four straight lengths, and that is most of the cost difference.

Insulating units for arched heads are made the same way but every one is bespoke, so there is no stock size to fall back on and a mistake is a full replacement.

Operation

Arched windows are usually fixed, because standard hardware does not fit a curved head and the geometry makes hinging awkward. The normal arrangement is a fixed arched head over an operable unit below — a casement, a double-hung or an awning — which gives the shape above and the ventilation, escape and cleaning access below.

That matters for compliance as well as convenience: a fixed arch contributes nothing to the openable area a habitable room requires.

Divided Lites in an Arch

Historic arched windows frequently carry divided lites radiating from the centre of the arc, like a fan. Reproducing that correctly means the bars follow the geometry rather than being set out square, and the bar width has to match the original. On a landmarked frontage this is exactly what the review examines. See our muntins and divided lites page.

Where Arched Windows Come Up

These describe the kind of work each area brings rather than any specific client project.

Pre-war apartment buildings — Prospect Lefferts Gardens, the Grand Concourse, upper Manhattan. Segmental and round-headed openings, often taller and narrower than anything standard, and frequently the reason a building cannot use catalogue windows at all. This is custom fabrication work rather than supply.

Brownstone and rowhouse districts — Park Slope, Carroll Gardens, Bed-Stuy, Harlem. Arched entrance heads, fanlights and parlour-floor windows, usually in historic districts where the geometry and the bar layout are governed by the approval.

Churches and institutional buildings — citywide. Gothic and large round-headed openings, often with leaded or stained glass, where restoration rather than replacement is usually the better answer.

New construction and renovation — Staten Island, Bergen County, Todt Hill. Arched heads as a design feature in larger houses, where the geometry can be set out cleanly from the start and the job is simpler as a result.

Send us photographs of the opening including a straight-on shot of the head, and we will arrange to template. We fabricate and install across Manhattan, Brooklyn, Queens, the Bronx and Staten Island, and throughout Northern New Jersey, the Jersey Shore, Philadelphia and the Lehigh Valley.

Recent project: Custom aluminum windows and a six-foot round window in Lakewood, New Jersey — including commercial entrance doors and waterproofing.