Box Sash Windows – Mayfair

Mayfair – Fully mechanically jointed Box Sash Windows in a wide range of finishes


The Mayfair makes an identical luxury statement embodied by traditional timber box sash windows. A frame with all of the attributes of KAT Elegance, plus the advantage of all frame and sash elements being mechanically jointed in a similar method to the time honoured British joinery techniques of traditional sliding sash windows.

Vertical sliding windows offer slim sight lines, a large glass area, a wide range of design options and flexible solutions for period properties or new build. This window style originated in the 17th century and continues to offer elegant glazed opening solutions with optimum ventilation and practicality guaranteed.

The KAT Mayfair is modern, secure, virtually maintenance free and manufactured from high impact, durable uPVC. They are hand crafted to your dimensions by us in Macclesfield, using very similar skills and techniques to those employed in our joinery workshops.

The thermal properties of uPVC are excellent and these windows can be supplied in a wide range of finishes. From six feet away it is extremely difficult to tell if the window is timber or uPVC.

Key features of Box Sash Windows – Mayfair

  • White Woodgrain finish as standard
  • Mechanically jointed outer frame and sashes
  • Mechanically jointed deep bottom rail
  • Slim meeting rail sightline 50mm
  • Hand crafted in our Cheshire factory
  • Virtually maintenance free
  • 146mm front to back frame depth
  • Black glazing spacer bar and gasket
  • Grey wool pile
  • Flush frame and cill features
  • Integral cill
  • Spiral sprung balance mechanism
  • KAT suited sash lifts, ‘hook and claw’ cam locks and ring pulls
  • Low emissivity 24mm double glazed argon filled sealed units
  • Window energy rating of C as standard
  • Max size w: 1.6m h: 3.0m - all frames made to measure


  • Special foil finishes will be considered

White foil grained finish as standard
Wide range of foil options available on request
General Description
A fully mechanically jointed, fully sculptured vertical sliding sash window, designed to replicate Georgian and Victorian box sash window designs, also known as 'sash and case' windows in Scotland. Every Mayfair sash window is handmade to bespoke sizes by KAT and meets the criteria required in most Conservation Areas.
24mm (4-16-4) double glazed sealed units
Planitherm Total Plus Low Emissivity, soft coat glass
Argon filled units
Black Warm Edge Spacer
U value of 1.4 on A rated
Hardware & Accessories
Cam catch handles and lift pulls available in;
white, antique gold, pewter, chrome and satin
Must be installed in accordance with Glass and Glazing Federation Guidelines
KAT – Macclesfield, Cheshire
All profiles are extruded to BS 7413
No run-through horn option
KAT bespoke 'white ash' internal georgian bar – fluted authentic
KAT bespoke 'white ash' external georgian bar - puttyline
Fire Escape Window
KAT bespoke spring loaded travel restrictor
'Tilt-in' facility on both sashes with KAT bespoke tilt latch knobs
Trickle ventilators
Product complies with BSEN 12608
Water Resistance 200 pa
Wind Resistance 1600 pa
Air Permeability 600 pa
Product Reference
White Foil both sides as standard with wide range of foil options available
Black spacer bar and gasket
Mechanically jointed outerframe
Mechanically jointed sash
Mechanically jointed deep bottom rail
Integral cill
Run-through horns
Slimline horizontal meeting rail
Spiral spring balance mechanism
Grey woolpile.
KAT bespoke 'Hook and Claw' cam catches and suited ring pulls
146mm outerframe
System Parameters
Maximum Width 1600mm depending on height of the frame. Please refer to the price grid for widths over 1600mm. Maximum Height 3000mm.
10 year warranty on all uPVC profiles
10 year warranty on spiral balances
1 year warranty on hardware and accessories
Window Energy Rating
Window Energy Rating A can be achieved



KAT only make bespoke windows to your exact specification. Each window is carefully designed and engineered to either replicate the authentic period features of an original design or to produce a contemporary window with a modern twist.

You choose the style, frame shape, hardware colour, glazing and other special features including authentic Georgian Bars to suit your property. We also offer ‘the solution’ for sensitive period buildings and for properties in conservation areas’. Our market leading box sash windows come with an extended 10 year warranty and design and engineered testing has demonstrated they have a life expectancy in excess of 25 years.



Material Information


All uPVC sections are extruded from high impact durable uPVC in accordance with BS7413.

Mayfair is supplied in a white ash grained finish as standard, with a wide range of foil finishes available.




All KAT box sash hardware is made in the UK to our design. There are a number of options to choose from sash lifts, locking cam catches, run through horns to spiral sprung balances.

Please consider your choice of ancillary hardware carefully because that is what you will eventually notice most when your products are installed. Choose from one of our suited finishes on our ring pulls and catches because it is attention to detail that helps make this unique product range so exciting.

Finishes available: –

  • White
  • Antique Gold
  • Chrome
  • Satin
  • Pewter




Safety & Security


Our Box Sash windows are designed to discourage a determined intruder, thanks to our locking cam catches and the reinforced meeting rail.

Safety & Security

Colour Options


Colour options: –

  • White ash grained both sides as standard
  • Wide range of foil finishes available on request