Bespoke,
Made to Measure

Custom secondary glazing solutions for arched, curved, circular and complex window openings

Bespoke, Made to Measure

Our Sheffield-based manufacturing facility gives us the in-house capability to produce secondary glazing solutions for virtually any window shape, size, or specification. From arched and bay windows to circular, curved, and angled configurations, we design and manufacture each unit to order.

Bespoke glazing is achieved primarily through a shaped timber subframe, which allows standard secondary glazing systems to follow complex reveals and non-rectangular openings without compromise to performance. For more complex profiles, our team can curve and bend aluminium sections directly in our own plant.

Particularly favoured on commercial projects, our bespoke range has been specified across church and heritage restorations, hotel refurbishments, hospital upgrades, and high-specification residential schemes where standard off-the-shelf units simply will not work.

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Technical Performance Data

Bespoke secondary glazing uses the same aluminium profiles and glass specifications as the standard Granada range. The performance data below reflects what is achievable across bespoke configurations — actual values depend on the base unit type, glass selection, and air gap specified.

Up to 54 dB Max Noise Reduction (Rw)
1.1 W/m²K Best U-value with DG unit
10 Years Product Guarantee
200+ RAL Colour Options

Values are Rw (dB) measured to BS EN ISO 717-1. All tests performed with a 200mm air gap (glass-to-glass) and a 6mm single-glazed toughened primary window in a hardwood frame. Deduct 1 dB for a 150mm air gap; deduct 1–4 dB for a 100mm air gap.

Secondary GlassRw (dB)
Weighted		Rw+C (dB)
Traffic weighted		Rw+Ctr (dB)
Low-freq weighted
4mm Toughened42–4941–4741–45
6mm Toughened43–5142–4942–46
6.4mm Laminate44–5143–5043–47
6.8mm Laminate44–5143–5043–47
8.8mm Laminate44–5144–5143–47
10.8mm Laminate45–5144–5144–48
12.8mm Laminate46–5145–5144–48
6.8/12/8.8 DG (hardwood)48–5248–5148
4/16/4 DG (uPVC primary)48–5348–5248
4/18/6.8 DG (uPVC primary)50–5449–5350

Values shown as achievable ranges across all applicable bespoke unit types at a 200mm air gap. Rw data extrapolated from physical tests at Element High Wycombe (23/06/22 & 12/07/22). DG acoustic values tested against stated primary window types. Actual performance depends on the base unit type and installation configuration.

Data extrapolated from physical testing at Element High Wycombe (23/06/22 and 12/07/22).

Download Performance Data Sheet: GSG-DS002 Rev A — Acoustic

U-values shown are combined whole-window system Uw values (primary window + air gap + secondary glazing), calculated to BS EN ISO 10077-1:2017 and BS EN ISO 10077-2:2017 with a 50mm air gap. These are not the centre-of-glass Ug values of the secondary unit alone. Values marked * are indicative figures calculated internally by Granada Glazing Ltd. and have not been externally verified — all other values are from calculations by Windata Ltd.

Hardwood primary - 4mm float glass, 60mm hardwood frame, Uw = 4.7 W/m²K | Steel primary - 3mm float, steel Crittall frame, Uw = 6.0 W/m²K
Secondary GlassHardwood Primary
U W/(m²K)		Steel Primary
U W/(m²K)
4mm K Glass1.45–1.51.55–1.61
6mm Toughened1.61–1.641.74–1.77
4mm Toughened1.62–1.641.75–1.78
6.4mm Laminate1.62–1.641.75–1.78
6.8mm Laminate1.61–1.641.74–1.77
4-16-4 Pilkington DG1.11.1–1.14
6.8mm Lam-16-6mm (Low-E)1.11.1
6mm K Glass1.4–1.51.54–1.59

* Indicative values calculated internally by Granada Glazing Ltd. - not externally verified. All other values from Windata Ltd. calculations per BS EN ISO 10077-1:2017 & BS EN ISO 10077-2:2017. DG units available exclusively on the Heavy Duty Hinged (HU-HD) base unit.

Download Performance Data Sheet: GSG-DS003 Rev B — Thermal

All dimensions in mm. Sizes are for guidance only and depend on glass type, subframe, and installation method. Contact us to discuss units outside the listed parameters.

Glass TypeMin WidthMin HeightMax WidthMax HeightAspect Ratio
(W:H)		Max Panel
Weight
4mm ToughenedMade to orderMade to orderContact usContact usVaries by unitVaries by unit
6mm ToughenedMade to orderMade to orderContact usContact usVaries by unitVaries by unit
6.4mm LaminateMade to orderMade to orderContact usContact usVaries by unitVaries by unit
6.8mm LaminateMade to orderMade to orderContact usContact usVaries by unitVaries by unit
8.8mm LaminateMade to orderMade to orderContact usContact usVaries by unitVaries by unit
10.8mm LaminateMade to orderMade to orderContact usContact usVaries by unitVaries by unit
12.8mm LaminateMade to orderMade to orderContact usContact usVaries by unitVaries by unit
24mm DG Sealed UnitMade to orderMade to orderContact usContact usVaries by unitVaries by unit
28mm DG Sealed UnitMade to orderMade to orderContact usContact usVaries by unitVaries by unit

Bespoke secondary glazing is installed using the same face fix and reveal fix methods as our standard range, adapted to the specific opening geometry. Shaped timber subframes are pre-drilled and countersunk to simplify on-site installation. For arched and circular units, the subframe follows the profile of the reveal, with the secondary glazing fixed directly to it. Our technical team can advise on the appropriate fixing method for each application at the quotation stage.

Our Sheffield-based manufacturing base is home to our very own painting plant, allowing you to choose from a comprehensive palette of more than 200 powder-coated RAL colours to achieve a precise match with your Granada secondary glazing system. Suitable for new developments, heritage buildings, and complex commercial environments, our finishes are specified to meet the requirements of each project.

Stocked colours available from short lead times

White
RAL 9003
Cream
RAL 9001
Van Dyke Brown
BS 08 B29
Anthracite Grey
RAL 7016
Black
RAL 9005
+200 RAL
custom colours

What is Bespoke?

Bespoke secondary glazing uses the same aluminium profiles as our standard range, shaped by a custom-formed hardwood subframe to follow arched, angled, bay, curved, or circular openings. For more complex profiles, aluminium sections can be bent in-house at our Sheffield facility.

Dimensions

All sizes made to order. Frame and panel tolerances: ±1.5mm

Maximum delivery size: 2,100 × 4,400mm

Glass Thickness Tolerances

  • Toughened: ±0.2mm
  • Laminated: ±0.4mm
  • Laminate interlayer: ±0.1mm

DG Units

24mm and 28mm double-glazed sealed units are available exclusively on bespoke Hinged Unit (HU-HD) configurations and are not available on arched or circular profiles.

Guarantee

All bespoke made-to-measure units carry a comprehensive 10-year guarantee covering frames and glazing, with a 2-year guarantee on moving parts.

Bespoke Project Case Studies

Compton House, Hay-on-Wye

Compton House, Hay-on-Wye

Secondary glazing was installed at Compton House, a Grade II listed townhouse within the Brecon Beacons National Park conservation area, to improve thermal and acoustic performance across five residential flats. Bespoke units were shaped to follow the original timber sash windows while retaining the building's historic fabric and complying with conservation area planning requirements.

Read full case study
Reuben College, Oxford

Reuben College, Oxford

A complex refurbishment of multiple historic buildings at Reuben College, including the Grade II listed Radcliffe Science Library, required secondary glazing shaped to suit a wide variety of non-standard window openings. Granada's bespoke capability allowed each unit to be tailored to the individual reveal geometry while delivering consistent acoustic and thermal improvement across the entire project.

Read full case study
What window shapes can be accommodated?
We can produce secondary glazing for virtually any window shape, including arched heads, circular, elliptical, angled, bay, and splayed configurations. For most shapes, the bespoke profile is achieved through a precision-formed hardwood timber subframe that follows the reveal geometry exactly. For more complex curved sections, our aluminium profiles can be bent in-house at our Sheffield manufacturing facility.
How are bespoke sizes specified and ordered?
All bespoke units are made to order from your supplied dimensions. Our technical team will work with you at the quotation stage to confirm the opening measurements, subframe profile, glass specification, and fixing method. We recommend a site survey for complex openings to ensure accuracy prior to manufacture.
Is there any difference in performance compared with standard units?
Bespoke units use the same aluminium profiles, glass specifications, and sealing systems as our standard range, so thermal and acoustic performance is directly comparable. Where the standard range data applies to the base unit type selected — for example a bespoke hinged unit — the same Rw and U-value figures will apply, subject to glass type and air gap.
Are DG sealed units available on bespoke configurations?
Double-glazed sealed units in 24mm and 28mm configurations are available on bespoke Heavy Duty Hinged Unit (HU-HD) installations. They are not available on arched or circular profiles, or on slimline variants, due to the structural requirements of the sealed unit.
What guarantee applies to bespoke units?
All made-to-measure bespoke units carry a 10-year guarantee covering the frame and glazing, with a 2-year guarantee on moving parts. Our customer care team is available at 01909 499 899 should any issue arise.