What is a sashed window?
A sashed window, commonly known as a sash window, features two framed panels of glass (or sashes) that can slide vertically past one another. These traditional windows are most often made of timber and have been a staple of British architecture for centuries. Each sash typically contains individual panes of glass, joined together with slender wooden glazing bars.
Why Were Sash Windows Invented?
The development of sash windows came from the need for more effective ventilation and better use of natural light. Prior to their invention, windows were simply holes in the wall, often covered with shutters, cloth, or leather. These crude openings allowed in cold, wind, and rain.
By separating the moving glass panels from the fixed frame, early sash windows allowed for better airflow and light, while still offering protection from the elements. The innovation of sliding panes meant that a window could be partially opened from the top or bottom to control air circulation more effectively.
How Are Sashed Windows Made?
Traditional sash windows consist of two sashes, each slightly taller than half the window opening, so they overlap and form a seal. These sashes slide up and down inside a larger frame fitted into the wall aperture. Early versions often had multiple small panes of glass held together by glazing bars (also known as astragals), due to limitations in early glassmaking techniques.
If you’re interested in how these differ across styles and time periods, we’ve covered that in our guide to the different types of sashed windows.
Where Did Sash Windows Originate?
The exact origins of sash windows are uncertain, but their use became widespread in the 17th century. French joiners introduced the vertical sliding sash, which quickly gained popularity in England. Queen Henrietta Maria is believed to have introduced them to Somerset House in London.
Earlier versions opened horizontally, but the vertical design became dominant and remains standard today.
What Is the Role of Pulleys and Counterbalances in Sash Windows?
As sash windows became larger, they also became heavier. To make them easier to open, a pulley and counterbalance system was introduced. Records from the Office of Works Account (1663) note that Thomas Kinward, the Queen’s Master Joiner, installed pulleys and lines in the windows of the Queen’s apartment in 1669.
Eventually, the mechanism became hidden within a box frame, and weights were used to balance the sashes. This allowed the windows to move smoothly and stay open at any height. We explore modern versions of this system in our article on sash window repairs and maintenance tips.
How Did Legislation Influence Sash Window Design?
The Great Fire of London (1666)
Following the fire, building regulations required that timber windows be recessed behind masonry to prevent flames from spreading. This led to the distinct Georgian style with flush-mounted sash windows.
The Window Tax
Introduced in 1696, the Window Tax charged homeowners based on the number and size of windows. To reduce costs, people used many small panes of glass rather than large ones. Ironically, the tax didn’t suppress demand for big panes; instead, it made them even more desirable as a display of wealth and status.
Interesting fact: ‘Horns’ were added to these larger windows to increase their strength without making them heavier by having to use thicker frames.
The window duty was removed in 1845 and fashion changed again as large windows with only one or two panes were affordable to the public.
You can read more about these adaptations in our post on replacing Georgian sashes.
Why Did Sash Window Styles Change Over Time?
Improvements in glassmaking led to fewer and larger panes in sash windows. The 19th century brought plate glass, which enabled expansive windows with minimal glazing bars. Later Victorian and Edwardian windows often combined large lower panes with decorative upper sashes.
If you’re interested in when to replace sash windows, check out our advice on restoration vs replacement.
Why Are Sash Windows Still Used Today?
Sash windows remain popular for their elegance and traditional character. They’re often required in conservation areas and listed buildings. Choosing the right materials and specifications is essential for these sensitive projects. Learn more in our article on how we tailor heritage windows for listed buildings.
What Materials Are Best for Modern Sash Windows?
Modern heritage sash windows often use high-performance timbers like Accoya® or Red Grandis, which offer exceptional durability and reduced maintenance, without the ugliness and environmental impact of PVC. You can compare these options in our blog on wooden sash windows vs plastic alternatives.
For even more realism and performance, our patented glazing systems can include astragals that outperform plant-on bars.
How Can Modern Glazing Improve Sash Window Performance?
Traditional sash windows were single glazed, offering little thermal or acoustic insulation. Today, vacuum glazing offers ultra-slim, high-performance glass that fits within heritage profiles.
This makes it ideal for listed buildings and conservation areas. We explain this in more detail in our case study on Quarndon sash windows.
What Are the Key Takeaways About Sashed Windows?
Sash windows have stood the test of time due to their elegant design, adaptability, and evolving technology. Whether you’re restoring original timber windows or replacing them with heritage-approved replicas, it’s vital to use high-quality materials and expert craftsmanship.
Need help choosing the right option for your home or project? Contact us to find out more.
Diagram courtesy https://homeharmonizing.com/how-to-replace-your-window-sash-cords-with-a-simple-process/