The History Of Sash Windows

In the 16th century throughout Europe wooden sliding shutters developed into glazed horizontal sliding windows and during the following century the vertical sliding sash window began to take its place.

The oldest known existing vertical sliding sash windows in Britain date from the late 17th century. It is unclear where the sliding sash originated but the word "sash" derives from the old French word "chassis" meaning a frame, which suggests that it was introduced into Britain from France.

Due to the high cost and the difficulty of manufacturing and transporting large panes of glass safely, the earliest sash windows had many small panes, and due to the large section of the glazing bars were very heavy. The technique of counterbalancing used for centuries in portcullises and drawbridges was incorporated to facilitate the easy opening and closing of the sashes. Cast iron or lead weights hidden in the hollowed out frame were used to counterbalance the sashes. These were hung on cords running over brass or hardwood pulley wheels mounted in the frame.

During the 18th century the classic Georgian style of two rows of three panes in each sash evolved and the thickness of the glazing bars was reduced to give an elegance typical of the era. At this time, rather than being made from hollowed out solid members the pulley stiles and linings of frame were constructed as a box to contain the sash-weights and brass or cast iron axle-pulleys were introduced.

The abolition of the tax on glass in 1845 slashed the price of glass and windows with only two panes per sash became common. Victorians would display their wealth by having windows with only one large pane in each sash. Horns (joggles) were added to the top of the bottom sash and to the bottom of the top sash to increase the strength of the sashes as the size of panes increased and the number of glazing bars diminished.

Changes in architectural styles around the beginning of the 20th century and the inherent draughtiness of sash windows reduced their popularity. Mass-produced wooden and steel casement windows became more economical and later in the century, as the sashes of older windows began to age and deteriorate, they were frequently replaced with casement windows often set into the original box frames.

With the introduction of cheaper UPVC windows with sealed unit double-glazing in the 1980s the process of replacement accelerated. Over the course of recent decades the sash window has all but disappeared from some areas, much to the disappointment of conservationists and people with an appreciation of the architectural heritage. Changes in energy conservation regulations also contributed to the decline in the use of wooden sliding sash widows.

In recent years incorporating effective draught-proofing techniques and sealed unit double-glazing into the traditional designs meant that sash windows could comply with the latest energy efficiency requirements. In addition a concern for the environmental impact of windows manufactured from UPVC, has led to a revival of interest in using wooden sash windows in new-build properties, repairing and upgrading existing wooden sash windows or replacing with new sash windows made from timber.