What is a sash window? - Westbury Windows and Joinery

What is a sash window?

westbury accoya sash windows

What do we know about sash windows? And why might self-builders or homeowners choose sash windows for a property?

The term ‘sash’ originates from the French word for ‘frame’. It, therefore, makes sense that the ‘sash’ in sash windows describes a single frame for glazing. But what else do we know about this beautiful window style? And why might a self-builder or homeowner choose sash windows for a property?

What are the key characteristics of a sash window?

Sash windows are typically formed of two moving panels (sashes). The most widely recognised variety is probably the sliding sash which has one panel at the front and one behind. Traditionally these are counterbalanced and slide over one another in vertical grooves by way of lead weights on cords. In more modern sash window production, springs have replaced the cords and weights.

Dating back to the 17th century and remaining very popular for more than two centuries, sash windows hold an important position in British architectural history. Traditional sashes are made up of small panes held together with glazing bars. The classic Georgian sash arrangement features a six over six-panel window, although eight over eight was also very popular during this era. Two over two dominated during the Victorian period, although the era paved the way for many more varieties, styles, and sizes to start gaining popularity.

6 over 6 sash window

Over the years, stylistic details of the humble sash window have evolved considerably. Notable designs include the Venetian, consisting of a central sliding sash sandwiched between two fixed side panes. The Queen Anne Revival style, featuring just one or two panes in the lower sash, topped by several panes in the upper sash. Some regions of the country favoured a horizontal sliding sash, and some sashes were arched in shape as opposed to rectangular, especially during times of Gothic and Regency revival.

Why choose sash windows?

For restoration or renovation projects, particularly in period properties, listed buildings or conservation areas, a genuine timber sash is possibly the only suitable window option. In these cases, the window needs to be chosen very carefully, as the smallest details can ruin an otherwise sympathetic restoration of a historic exterior.

There is a common misconception that timber windows are high maintenance but quality wood is actually an extremely durable and stable material that offers outstanding insulating properties with minimal upkeep required. Wood can also be stained or painted to create the desired effect and a plastic replica will simply not be able to achieve the same results.


Choosing a premium grade wood, that is knot free, will produce a  timber sash window with superior performance and a stunning finish. A wood like Accoya ® is non-­toxic and can withstand extreme external environments. Accoya ® is also hardwearing and versatile, with the benefit of being low maintenance and easy to treat in a range of finishes.

Sash windows are also the obvious choice of window for any traditionalist housebuilders and developers who are seeking to replicate a classic design using modern materials and manufacturing processes.

Traditional aesthetics with innovative design

Available with traditional cords and weights or with pre-tensioned heavy duty balances, Westbury’s engineered timber sash windows make a unique and elegant addition to any new build or refurbishment project. You can find out more about our sash windows here, or please feel free to contact us.