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How Do Sash Windows Work?

by Francesca Coleman Carr

Sash windows work on a pulley system. The timber sash windows we build and install are made up of many individual parts that all contribute to the unique aesthetic of these beautiful windows. A typical sash window has a sill, top and bottom rails, timber linings, sash weights, and cords. When all of these aspects work in harmony, the sash window is able to move freely and function effectively.

But how do sash windows work? Well, each window consists of two window frames (otherwise referred to as sashes) that are both suspended by a cord. The cord from each window frame passes through a pulley system that has a heavy counterweight on the end that allows each frame to be opened and closed independently of the other.

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How Sash Windows Work is Not Immediately Visible

Sash windows are designed to work in such a way that many of the intricate mechanisms that provide functionality are hidden. For example, the counterweight comes in the form of a steel, cast-iron or lead sash weight and is connected to the window via a sash cord. The sash cord runs over the top of the pulley and along the top rail, and is concealed in the window frame so that it is not immediately visible. By concealing the pulley system of sash windows within the frames, homeowners are able to enjoy the aesthetic beauty of their windows without distraction.

High Functioning Traditional Sash Windows

Traditional timber sash windows function seamlessly on a weight and cord system. The weight is connected to the window sash by the cord that runs over the hidden pulley. The counterbalance created between the weight and the sash window facilitates enough resistance for a smooth window opening.

Sash windows can be fitted with complex hinge systems that allow the window to be locked on one side while the counterbalance on the other side can be detached. This is a helpful feature that can allow the window to be opened to let fresh air into your home, to get out, or to clean.

The Importance of Traditional Window Sills

An important design feature of many sash windows is the traditional sill that is fitted at the base of each sash window. This sill is fitted internally at the base of each sash window to ensure that rainwater will drain away from the window. The reason traditional window sills are such an important feature for sash windows is that they prevent rainwater build-up within the frame which can cause significant rot issues over time.

How Do Sash Windows Work? Terms You Need to Know

1. Top rail: this is the top horizontal frame of your window.
2. Sash cord: this is what runs over the pulley wheel and holds the weights. When it needs replacing, it can be bought in rolls (waxed sashes are best).
3. Weight pocket: the weights hang in the pockets that are created by the timber linings on either side of the window.
4. Parting bead: this is a long, narrow seal that fits the box frame to form separate channelers for both the upper and lower sashes to run in. It also helps to hold the top sash in place.
5. Meeting rails: the horizontal framing members which meet the two sashes together in the middle.
6. Horizontal sill: a board fitted horizontally across the internal base of the sashes and shaped in such a way that water flows away from the window to prevent rot and leaks.
7. Weight: a pair of lead weights that are hung on the sash cord to provide counterbalance for each sliding sash.
8. Timber linings: these are the sections that form the casings of the box frame. They are made hollow so that they can house the weights.
9. Pulley wheel: a pulley that is situated in the top of the pulley lining so that the sash cord can pass over it and counterbalance the weights.

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How Do Sash Windows Work in Contrast to Box Sash Windows?

Many people get confused by the term ‘sash windows’ and the term ‘box sash windows’. While in the US, these two windows are often very different, in the UK the terms are frequently used to describe the same thing. Although historically box sash windows were heavier than sash windows and popular in stately homes, both terms are used interchangeably in the sash window industry and therefore, they work in just the same way!

Working Sash Windows Require Professional Fitting

Sash windows work most effectively when they have been built and installed by professionals that are qualified and experienced in the sash window and double glazing industry. As you can tell from the points mentioned above, sash windows work off of an intricate pulley and weight system, so it’s important they are installed properly to ensure maximum functionality, security, and energy-efficiency.

Have your sash windows installed by a professional today so that you can enjoy all the benefits of sash windows for yourself.

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