Sash windows use the traditional vertical sliding design where they feature two vertical sliding panels that move within the window frame. They are often called:

·       Sliding Sash windows

·       Hung Sash windows

·       Box Sash windows

Timber Box Sash windows have withstood the test of time as the preferred window model in the UK. Contrary to common misconceptions, timber sash windows can exhibit longevity spanning across many years to come. There are examples of said windows which have lasted for 100 years as they have been taken care of properly.

Benefits of these windows are:

1.         They let a lot of light through the large, glazed surface area.

2.         Strong by design (we manufacture our products in hardwood only).

3.         Unlike casement windows they can’t be blown opened or closed.

4.         Both vertical panels are easy to open which allows for good air flow.

At International Windows Group LTD, we exclusively offer top-tier box sash windows renowned for their exceptional quality throughout London. Our products are a perfect mix of great materials and modern technologies, complemented by years of invaluable experience that has earned the trust of numerous clients. We assure clients of long-lasting longevity for their windows by spraying four layers of waterproof paint on our products.

Additionally, our windows are compatible with conservation area by using Victorian style design.

Please, scroll below to see more information.

Timber Sash Windows Construction On Weights

Timber Sash Windows Construction On Springs


Pine, meranti, oak and other 3-layer glued wood


Windows are sled up and down.
Drive supported with lead weight or springs placed in window frame.


Scumbles emphasizing wood structure, opaque in full RAL palette 4-layer system for painting with highly dilutable ecological paints, single and double colored joinery


Standard: “24 mm thermofloat” glazing Ug= 1,1 W/m2K
Optionally: Triple panel, Safe and anti-burglary window panels, Absorptive and reflective panels, Sound absorption panels, Ornament, satin panels.


Standard: Up-down slide


Standard: ferrules of renowned ferrules of renowned companies: Mightons Products. Drive supported with lead weight or springs placed in window frame.


Available standard patterns below


Q-lon made by Schlegel


Bilateral silicone covering


Mullions bilaterally glued in a color of the window


Standard – Aluminum
Optional – Plastic-warm frame colors: swhite, black, light brown, dark brown


Horns, vents, restricktors,