The different types of sash window

Sash windows have always been popular

When choosing to replace a window, customers are faced with various types and styles. The two most popular types of windows for installation in the home are the casement and the sash windows.
A casement window has hinges on the side or top, allowing the window frame to open outwards or inwards. A sash window overlaps two or more sliding panels to create an opening gap.
You can have one or more sliding panels that can slide horizontally or vertically, although the latter is by far the most common.
Sash windows have existed since the late 1700s. The design has not been much improved over the years except for modern materials that make them more robust, long-lasting, and easier to maintain.

Who invented the sash window?

The identity of the original inventor of the sash window has been lost in time. Some historians suggest it was an English invention, while others credit the Dutch. What is known is that early English sash windows date from the late 17th century but did not become commonplace for about 200 years. By the Georgian period, they were becoming the window of choice for architects and builders, and in Victorian times, it was unusual to use any other design. It was only with the advent of modern materials for window manufacture that sash windows began to fall out of fashion. But they are still prevalent in many homes thanks to their elegance and classic design.

How does a sash window work?

Many period properties from the Georgian and Victorian eras were built with sash windows. Modern-day heritage homeowners prefer sash window replacement to ensure they are in keeping with the period style. A sash window usually has two frames, one positioned above the other so that either panel can slide up or down to create a window opening. Although most sash windows slide vertically, some will open horizontally. Sash windows often come with a counterbalance weight to help make opening and closing easier. It is usually concealed inside the frame with hidden pulleys. As the pulley system is shielded inside the frame, it rarely breaks down and can outlast the life of the window frame itself. In a traditional sash window, both frames include several small panes of glass, often called lights, held in place by thin bars. In the early 19th century, the technology to create large glass panels did not exist, so the only way to fill a large frame was with small glass panes. By the time technology developed to allow the manufacture of large panes of glass, the small pane design had become iconic, and the use of small glass panels remained. Nowadays, sash windows retain the traditional configuration of two frames with six small panels each, although many configurations are possible.

What are single and double-hung sash windows?

Window installation customers may come across the terms 'single-hung and 'double-hung' when choosing a sash window. Both types of sash windows look precisely the same; the difference is whether one or both frames are moveable. With a 'single-hung sash window, one frame is permanently fixed in position while the other frame slides over it. With a double-hung sash window, both panels are moveable. Single-hung windows are cheaper as there are fewer moving parts, and installation is slightly more manageable. They can be advantageous if you have many sash windows to replace in an old property. Double-hung sash windows are a relatively recent innovation. As a result, they may not match the original Georgian windows perfectly, but there is virtually no difference aesthetically. Double-hung windows are more expensive but do have the advantage of being able to open top and bottom. They can also be easier to clean.

What are flush sash windows?

Flush sash windows describe windows where the inner and outer frames are flush with each other to give a flat overall surface. As a style, both flush casement and sash windows have been around for a very long time. Most older properties (where the timber windows have survived) will have windows of this type. In the 1950s, timber windows with a lipped design, where the window frame sits on top of a surround, became popular, and the trend continued with the growth of double glazing. The emergence of window manufacturing materials other than timber, such as PVCu and aluminium, triggered a resurgence in the traditional flush window design. Flush sash windows have clean, uncluttered lines that look elegant and graceful, with sashes fitting flush to the face of the window. Modern flush sash windows often have inner and outer frames that appear the same width. They are said to have 'equal sightlines', which can add further to a property's elegant appearance.

More on choosing windows

Choosing new windows
Energy-efficient windows
Types of glass windows
Flush frame windows