Bow Windows Explained

A bow window is a curved window assembly that projects outward from the wall, built from four or more equal-width panes joined at gentle, identical angles to form a smooth arc. It is one of the most distinctive styles in UK domestic glazing, found most often on Victorian and Edwardian terraces where the rounded curve complements the period brickwork. A three-section uPVC bow costs £1,250 to £1,500 fitted in 2026, while a six-section bow reaches £2,340 to £3,400. You can price your own configuration in the bow window calculator, or browse the wider window style guides if you are still weighing your options.

What is a bow window?

A bow window projects from the wall as a continuous, gently curved arc. The key characteristic is that each pane is the same width, and the angle between adjacent panes is equal along the whole assembly. A three-section bow joins its three panes at two shallow angles; a six-section bow joins six panes at five slightly larger angles, but because there are more of them the overall form reads as a smooth curve rather than a polygon. The more sections, the broader the projection and the more convincingly rounded the result.

In practice, each pane within the bow can be specified as a casement unit (hinged at the side and opening outward) or as a fixed light with no mechanism. Most homeowners choose opening panes for the centre sections, where ventilation is most useful, and fixed lights for the narrower end sections. In uPVC, the entire assembly arrives from the factory as a single welded frame, which speeds installation and improves the seal between sections. The frame profiles are the same as a standard casement, so the glazing specification, hardware and weatherproofing follow established practice.

A bow window is not just a prettier casement. The curved projection adds half a square metre or more of internal sill space, which most homeowners use as a reading seat, a plant shelf or extra worktop in a kitchen. In uPVC it is genuinely affordable for what you get in return.

Tom Bradley, FENSA-registered installer

Bow window vs bay window: what is the difference?

The terms are regularly used interchangeably, but they describe structurally different products. A bay window projects in three flat sections, with the two side sections angled back to the wall at 90, 135 or 150 degrees. The centre panel is wide and vertical; the flanking panels are narrower and set at an angle. The assembled shape is angular, with clearly defined corners, and it often sits on a dwarf wall with a flat roof or pitched canopy above. Our guide to bay windows explained covers the three bay configurations and their costs in detail.

A bow window, by contrast, uses four or more sections of equal width, joined at identical shallow angles. There are no prominent corners because each angle change is modest. Seen from the street, the overall outline is curved. Seen from inside, the internal sill follows the same curve, creating a window seat or shelf that flows naturally. The curved head (the top frame member) and curved sill are the two most complex elements to manufacture, which is why a bow window in timber is considerably dearer than in uPVC, where factory-bent profiles and welded corners reduce the craft element.

As a rough guide to placement: bow windows appear most often on the front elevations of Victorian and Edwardian terraces and semis, where the rounded profile echoes the period detailing. Bay windows are more common on inter-war semis, 1960s estates and post-war housing, where the wider, flatter facade suits the bolder, more angular bay form.

Bow window costs in 2026

Section count is the single biggest variable in bow window pricing. A wider opening with more sections adds both material and installation time. The table below shows fully fitted costs in uPVC, meaning supply, delivery, removal of the existing window, installation, sealing and the FENSA certificate are all included. The three-section option is the entry point and typically fits openings of around 1.8 to 2.2 metres; a six-section bow suits wider openings of 2.8 metres and above.

Source: DGCC 2026 dataset (per-bow by section count); aluminium and timber follow the site material uplifts.

Aluminium bow windows carry a premium of roughly 30 to 40% over the equivalent uPVC figures, reflecting the slimmer sight lines, longer anticipated lifespan and greater rigidity of the aluminium profiles. Timber bow windows run roughly 60 to 110% above uPVC, a wide range because the uplift depends significantly on timber species (softwood is at the lower end, hardwood at the upper), the complexity of manufacturing the curved head and sill, and finishing costs. For a complete view of how material choice affects cost across all window types, the window costs hub sets out the full picture by style and material.

Which homes suit a bow window?

Best Buy A bow window is at its best on a period property where the smooth curve reads as an authentic architectural feature. Victorian and Edwardian terraces and semis are the natural home for this style. The curved projection adds internal floor area at the window, lifts natural light on the front elevation and improves the street presence of the property in a way that a flat casement cannot match. In a front reception room or a bay-fronted bedroom, a well-fitted bow window is one of the more effective single-window upgrades available.

In terms of room placement, bow windows work well in front reception rooms, bay-fronted bedrooms and rear-extension kitchens, where the curved sill can serve as a casual breakfast bar or plant display. For homeowners assessing whether the investment in a bow window is proportionate to the size of the property, the cost by house size guide helps set realistic budgets for the overall glazing project.

When a bow window is the wrong choice

It depends On a modern detached house or a clean-lined new build, a bow window can look out of keeping where the architecture calls for flat, uninterrupted glazing. For those properties, the simpler and cheaper casement window is almost always the better choice, and at £400 to £1,000 per window in uPVC it leaves budget for more units across the house.

The projecting footprint is another practical consideration. A six-section bow can project 600 to 700 mm from the wall face, and if the front of the property is close to the pavement or a boundary, that projection may push the limits of permitted development. Some front gardens are also too narrow to accommodate a deep bow without it looking cramped. Always check projection depth against the available space before committing to a section count.

On upper floors, the additional weight of the bow frame and the need to maintain weatherproofing around the projecting structure add complexity and sometimes cost to the installation. A competent installer will assess the lintel, the existing opening and the structural situation before quoting. If a quotation arrives without a survey visit, that is a warning sign. Our guide on avoiding overcharging sets out what a thorough quote should include, including the survey, the removal costs and the certificate.

I have seen bow windows quoted on houses where nobody has checked the lintel. The customer pays a deposit, the old window comes out, and then everyone realises the opening is not wide enough or the head needs rebuilding. Get the survey done before you sign anything. A professional installer will insist on it.

Tom Bradley, FENSA-registered installer

The verdict on bow windows

If your home suits the style and you have a suitable opening, a bow window in uPVC is excellent value for the kerb appeal, light and internal sill space it delivers. A three-section bow at £1,250 to £1,500 fitted is a realistic starting point for period terraces with standard front window openings. Step up to a five or six-section bow and the curve becomes genuinely dramatic, though the investment rises to £1,950 to £3,400 accordingly.

For properties where the bow window is architecturally right, it is one of the most impactful single-unit glazing changes available. Run the numbers in the bow window calculator, compare the profile against the boxier alternative in the bay windows guide, and review the full cost landscape across all styles in the costs hub before getting quotes.