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Bay windows present unique challenges for secondary glazing. Learn about the options, installation methods, and specifications for Victorian and Edwardian bays.
Bay windows are one of the defining features of Victorian and Edwardian London. Whether canted (angled), curved, or square, they flood rooms with light, create architectural interest, and have graced the capital's terraces for over 150 years. They also present particular challenges for secondary glazing.
Here's our specialist guide to protecting and improving London's bay windows.
The most common type in Victorian terraces—three flat windows arranged at angles (typically 45° or 30°). The side windows return to the main wall at an angle.
Secondary glazing approach: Three separate units following the same angles, or a single faceted unit spanning the entire bay.
Three windows at right angles—a flat front with two 90° returns. Common in later Victorian and Edwardian properties.
Secondary glazing approach: Three independent units, or an integrated corner-return system.
A continuous curve, sometimes with multiple small panes, sometimes with large curved glass. Most commonly found in Georgian and Regency properties.
Secondary glazing approach: Curved secondary glazing is possible but requires bespoke manufacturing. Faceted approximation is an alternative.
Each window within the bay receives its own secondary glazing unit, mounted to the individual reveals.
Advantages:
Disadvantages:
A single secondary glazing system spans the entire bay, with glazed panels joined at the angles.
Advantages:
Disadvantages:
Side panels as separate units, centre panel independent. Allows opening of side windows for ventilation while maintaining sealed centre.
This often provides the best balance of performance and practicality for typical Victorian bays.
The critical challenge for bay window secondary glazing is the corner junction. Options include:
A vertical aluminium post at each corner angle, with glazed panel
For expert secondary glazing advice and free consultations for listed buildings in London, contact Secondary Glazing Specialist on 020 7060 1572.
Penny Hargreaves
Heritage Acoustics Writer
Bay windows are one of the defining features of Victorian and Edwardian London. Whether canted (angled), curved, or square, they flood rooms with light, create architectural interest, and have graced the capital's terraces for over 150 years. They also present particular challenges for secondary glazing.
Here's our specialist guide to protecting and improving London's bay windows.
The most common type in Victorian terraces—three flat windows arranged at angles (typically 45° or 30°). The side windows return to the main wall at an angle.
Secondary glazing approach: Three separate units following the same angles, or a single faceted unit spanning the entire bay.
Three windows at right angles—a flat front with two 90° returns. Common in later Victorian and Edwardian properties.
Secondary glazing approach: Three independent units, or an integrated corner-return system.
A continuous curve, sometimes with multiple small panes, sometimes with large curved glass. Most commonly found in Georgian and Regency properties.
Secondary glazing approach: Curved secondary glazing is possible but requires bespoke manufacturing. Faceted approximation is an alternative.
Each window within the bay receives its own secondary glazing unit, mounted to the individual reveals.
Advantages:
Disadvantages:
A single secondary glazing system spans the entire bay, with glazed panels joined at the angles.
Advantages:
Disadvantages:
Side panels as separate units, centre panel independent. Allows opening of side windows for ventilation while maintaining sealed centre.
This often provides the best balance of performance and practicality for typical Victorian bays.
The critical challenge for bay window secondary glazing is the corner junction. Options include:
A vertical aluminium post at each corner angle, with glazed panels either side. Creates a clean junction but adds visible framework.
Glazed panels butted together at the angle with silicone seal. Minimal framework but requires precise manufacturing and careful sealing.
One panel slightly overlaps the adjacent panel at corners. Simple but creates visible step and potential acoustic weak point.
True curved secondary glazing requires glass bent to match your bay's radius. This is:
For tighter curves or budget constraints, a faceted approximation using multiple flat panels can achieve excellent results at lower cost. With slim frames and careful angle matching, the faceting is barely noticeable.
Side-hung panels that swing inward. Works well for individual units but awkward for large centre panels. Good for ventilation and cleaning access.
Matches the operation of original sash windows. Excellent for maintaining consistency of operation across your windows. Slightly more complex for angled bays.
Panels slide sideways behind each other. Works well in bays where vertical operation is impractical. Allows large openings with panels stacked.
Fixed panels that can be removed entirely for cleaning or summer. Lower cost, maximum acoustic performance, but requires storage for panels when removed.
Bay windows are often noisier than flat windows because:
With properly specified secondary glazing, bay windows can achieve the same 45-54dB reduction as flat windows—but corner details must be carefully resolved.
Bay windows are also thermal weak points because:
Secondary glazing dramatically improves bay window thermal performance. Combined with attention to the bay roof (if accessible) and any floor voids, the improvement in room comfort is substantial.
Bay windows are often architecturally significant. In listed buildings and conservation areas:
With recessed installation and slim profiles, secondary glazing in bay windows is typically undetectable from the street.
Bay window secondary glazing costs more than flat windows due to complexity:
These prices assume standard acoustic specification. Premium glass specifications (10.8mm acoustic laminate) add approximately 30%.
Bay windows require precise measurement and careful design. We survey:
This ensures your secondary glazing fits perfectly and operates properly.
If you have bay windows that need acoustic or thermal improvement, request a survey. We'll assess your specific bay configuration and recommend the optimal approach.
Call 020 7060 1572 to discuss your bay window project.
London's leading secondary glazing specialists for Grade I, Grade II, and Conservation Area properties. Every project begins with a complimentary heritage survey.
