Vertical sliding box sash windows offer slim sight lines, a large glass area, an extensive range of design options and flexible solutions for period properties or new builds.This window style originated in the 17th century and still offers elegant glazed opening solutions with optimum ventilation and practicality guaranteed.


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.

Box Sashed Windows – Classic

The KAT Classic is modern, secure, nigh on maintenance free and manufactured from high impact, durable uPVC. uPVC box sash windows authentically imitate the look of timber but are virtually maintenance free and are hand crafted to your dimensions.

Box Sash Windows – Elegance

The KAT Elegance is modern, secure, almost maintenance free and manufactured from high impact, durable uPVC. The Elegance has all the features and benefits of the KAT Classic range but with an even more substantial frame and flush features.

Box Sash Windows – Mayfair Elegance

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.


Every window is methodically designed and engineered to either replicate the authentic period appearance of an original design or to produce a contemporary window with a modern twist.


You select the style, frame shape, hardware colour, glazing as well as other individual features including authentic Georgian Bars to suit your property. We also offer ‘the solution’ for sensitive period buildings and for properties in conservation areas’. The market leading box sash windows we offer 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. The Mayfair Elegance box sash window we offer are supplied in a white ash grained finish and we can paint with almost any RAL colour.


All KAT box sash hardware is made in the UK to their design. There are a whole host of options to choose from such as 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 the suited finishes on the 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.

Colour options

  • White ash grained both sides
  • Painted RAL colour finish in almost any RAL colour on grained finish