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How Do Sash Windows Work?

What is a Sash Window?

In simple terms, a sash window consists of one or more movable panels or sashes, which form a basic frame to hold variable panes of glass. These are separated by glazing bars and moulded strips of wood, which determine the core design of the window and their primary functionality.

A typical sash window is made up of numerous individual parts including a sill, top and bottom rails, sash weights, cords, and timber linings. These all contribute to the unique look and aesthetic values of a sash window, whilst they also work in harmony to ensure that it moves freely and is fit for purpose.

How Does a Sash Window Work?

In order to facilitate the window’s movement, a glazed panel is balanced by a counterweight, in the form of a steel, cast-iron or leaden sash weight. This is connected to the window via a sash cord, which is usually braided and runs over the top of a pulley along the top rail. The addition of a bottom rail completes the frame and window design; wag tails are also used to separate the weights and allow smooth and seamless movement.

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From a design perspective, it is important to note that the sash weights are not visible because they are concealed within hollow timber linings that form the basic box frame. It’s also important to mention that a horizontal board or traditional sill is fitted internally at the base of each sash, and this has a specific shape which ensures that rainwater will flow away from the window (this is an important feature and function, as water may otherwise accumulate within the frame and cause significant rot issues over time).

Repairing and Restoring Sash Windows

Given that the function of your sash window relies on individual elements working seamlessly, repairs and restorations should always be carried out by experts. Breakage of the sash cord can be particularly challenging, for example, as this requires the disassembly of the pulley wheel, the trim pieces and the weights to access; that’s why knowledge and practical experience is essential.

Sash windows are undoubtedly unique, both in their appearance and the way in which they work but that doesn’t mean that you should rush to replace them if problems occur. At Fortis & Hooke, we are dedicated to restoring all sash windows, regardless of the problem, in a bid to breathe new life into these wonderful features and eliminate the need for costly window replacements.

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