Arched Sash Windows

The Crown of the Georgian Facade

An arched sash window — a working box sash whose top sash rises into a semi-circular head — is the signature of fine Georgian and Victorian architecture: fanlit hallway windows, stairwell arches, the centre window of a symmetrical five-bay front. And it is one of the hardest windows in joinery to make properly, which is why so few companies offer one that actually slides.

We build them daily. Better: we let you build one yourself. Our online configurator draws your arched sash in live 3D — the curved head, the glazing bars, even the weights and cords inside the box — and prices it instantly as you change every option.

Arch Shapes Available

• Semi-circular — a perfect half-circle head, the classic Georgian form. Rise equals half the width.
• Gothic (pointed) — two arcs meeting at an apex; see our dedicated gothic sash windows page.
• Segmental — a shallow arc, subtler than a half-round; common on late-Victorian and Edwardian streets.

Glazing Bar Patterns

• Hub & spoke — the radial fan: a half-ring hub at the centre of the spring line with spokes radiating to the curve. Single, double, or triple concentric rings.
• Half-hub — a simpler fan with the hub ring only at the base, spokes running clear to the arch.
• Intersecting — vertical bars branching into interlacing arcs, continuous with the grid below.
• Georgian match — the lower sash carries a conventional bar grid, columns aligned precisely with the pattern above.

Every pattern is set out geometrically by the configurator — spokes at true angles, rings concentric with the arch — so what you approve on screen is what the workshop builds.

How It Is Built

The curved head is laminated from engineered hardwood in our workshop, machined to the exact radius of your opening, with mouldings run around the curve to match the straight sections. The sliding mechanism is the traditional one — cast-iron weights on waxed cords over brass pulleys — engineered for the shorter weight boxes an arch imposes: upper weights hang deep in the box, lower weights high beside the pulleys, so nothing fouls, ever.

The head is glazed with a shaped double-glazed unit made to each window's template, curved warm-edge spacer included. Slim heritage units available for listed buildings.

Guide Pricing

Guide prices, August 2026, including double glazing, single colour finish and standard hardware. The configurator prices your exact dimensions, timber, colour, glazing and ironmongery live.

Conservation Areas

Arched sashes are focal windows — planning officers notice them first. In conservation areas we replicate the existing arch geometry, bar pattern and sightlines like-for-like, and supply drawings for your application. Where the original is beyond saving, we template the masonry opening itself: after a century of settlement, few arches are perfectly true, and the window must be made to the opening, not to a drawing.

Frequently Asked Questions

Do arched sash windows open?
Yes — the lower sash slides on weights and cords like any box sash. The arched upper sash can be supplied fixed or sliding.

Can you match my existing arched window?
Yes. We survey and template the opening, match moulding profiles and glazing bar layout, and manufacture like-for-like — the standard required in conservation areas.

How much does an arched sash window cost?
From about £2,670 for a typical 1000 × 1940 mm window, plus £280–£680 for fan or tracery glazing bars. Exact pricing is instant in the configurator.

Is the curved glass double glazed?
Yes — every head is glazed with a shaped sealed unit made to that window's radius, with a curved spacer bar. Slim heritage units are available.

Related: gothic sash windows · fanlights & sunburst windows · all arched & shaped windows · standard box sash windows