uPVC Box Sash Windows

Quality uPVC Box Sash Windows designed & manufactured in the UK


Vertical sliding box sash 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 Classic is modern, secure, virtually maintenance free and manufactured from high impact, durable uPVC. uPVC box sash windows authentically replicate the look of timber but are virtually maintenance free. They are hand crafted to your dimensions by us in Macclesfield, using very similar skills and techniques to those employed in our joinery workshop.

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 uPVC Box Sash Windows

  • Hand crafted in our Cheshire factory
  • Virtually maintenance free
  • Will not stick, rot or warp
  • 128mm front to back frame depth
  • 150mm integral cill
  • Spiral sprung balance mechanism
  • Key locking cams with suited sash lifts and ring pulls
  • Fitted with draft excluding woolpile and seals
  • Low emissivity 24mm double glazed argon filled sealed units
  • Window energy rating of C as standard
  • All frames made to measure
  • Max size w: 1.6m h: 3.0m

White PVCu
• White ash both sides
• Cream ash both sides
• Golden oak both sides
• Golden oak out / white PVCu in
• Rosewood both sides
• Rosewood out / white PVCu in
Wide range of RAL finishes also available
General Description
A fully welded, vertical sliding sash window, designed to replicate Georgian and Victorian box sash window designs, also known as 'sash and case' windows in Scotland. Every Classic window is handmade to bespoke sizes by KAT.
24mm (4-16-4) double glazed sealed units
Planitherm Total Plus Low Emissivity, soft coat glass
Argon filled units
Warm Edge Spacer (Black or Grey)
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
150mm or 210mm integral cill
Run-through or plant-on horns
White, black or silver spacer bar
Deep bottom rail
Integral Georgian bar to double glazed unit 18mm or 25mm width
Traditional face fixed Georgian bar to glazed unit 22mm or 30mm width
KAT bespoke spring loaded travel restrictor
Tilt-in facility on both sashes with KAT bespoke tilt latch knobs
Arched head frames
Trickle ventilator
Fire Egress
Product complies with BSEN 12608
Water Resistance 200 pa
Wind Resistance 1600 pa
Air Permeability 600 pa
Product Reference
Fully welded outerframe and sash
Mechanically jointed deep bottom rail option
128mm outerframe with integral cill
Black gasket on bead. Grey woolpile.
KAT bespoke 'Hook and Claw' cam catches and ring pulls
Spiral spring balance mechanism
System Parameters
Maximum Width 1,600mm
Maximum Height 3,000mm
10 year warranty on all PVCu 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. We have a wide range of timber alternative grained finishes and we can paint with almost any RAL colour.




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


A little time and care with your choice of colour is advised and your selection should be influenced by the style of your property, surrounding architecture or your others windows and doors.

Colour options: –

  • White uPVC

Grained Finishes

  • White ash both sides
  • Cream ash both sides
  • Golden oak both sides
  • Golden oak out / white uPVC in
  • Rosewood both sides
  • Rosewood out / white uPVC in

Or choose from a wide range of RAL colours