Replacement box sash window with slimline double glazing

The box sash window is a classic window design that features in many Georgian, Victorian and Edwardian properties throughout the UK. Because of their elegance and simplicity, box sash windows also feature in newer properties or extensions where an architect is looking for simple, clean lines, or to create a traditional look.

Slim section sizes and narrow profile glazing bars are the key to an elegant box sash window. Achieving this look presents a challenge for modern window manufacturers, looking to replicate or keep such slim timber sections, while adding modern improvements such as thermal and sound insulation.

Luckily it is in fact possible to have the ‘best of both worlds’ and keep the slender elegance of traditional box sash windows, even if the window specification is upgraded to include high performance features such as double glazing.

At Timbawood we offer a full range of bespoke options for timber box sash windows, and specialise in creating elegant period designs which feature the latest modern security and comfort.

Our most popular range for period properties is our conservation range. This made to measure range features an array of options including our elegant slimline double glazing that looks just like single glazing, and our most slender profiles, mouldings and glazing bars which can be tailored to match your property exactly.

Even though our slimline double glazed units start from just 11mm thick, we greatly enhance their thermal efficiency by using a softcoat Low E pane, warm edge spacer bars and krypton or xenon gas fill.

Timbawood box frame depths range from 140mm to 168mm, with bespoke options as slim as 120mm that can meet part L building regulations for thermal efficiency. We offer multiple solutions for replacing box sash windows, irrespective of the check reveal depth.

Whatever the style or age of your property, we can accommodate a full range of bespoke options, including –

  • Exact-match detailing with your choice of moulds, horns and profiles
  • Choice of the finest timbers including Accoya, Sapele and Oak
  • Specialist glazing options including acoustic glass, laminated security glass and slimline double glazing that looks just like single glazing
  • Applied glazing bars or solid glazing bars
  • Hand-puttied or timber beaded
  • Bespoke hardware – High security fasteners, locks and restrictors 
  • Variety of finishes including dual colour and stained oak
  • Full perimeter draught proofing
  • Full design, supply and install service

If you would like to speak to one of our experts about your window project, please get in touch.