Window and door designs have evolved dramatically over the centuries, with London standing out as a city where architecture beautifully intertwines tradition with innovation.

Once renowned for having some of the finest joinery in the world, London’s craftsmanship took a downturn during the mid-20th century, as mass production led to a decline in quality.

However, today, modern techniques and renewed attention to detail have brought British joinery back to its former glory. Some british window makers have not only gone back to the original craftsmanship of the windows, but surpassed it.

At the forefront of this revival is Todi & Boys, a London sash window company that masterfully combines heritage sash window designs with cutting-edge technology, delivering products that honour the past while meeting the rigorous standards of contemporary living.

Windows Through the Ages: From Casements to Sash

Windows have always been a staple of architectural design, with examples of advanced glass-making techniques dating back to the Roman era, when glass within windows were employed to enhance insulation and protection from the elements.

For centuries, casement windows dominated European architecture. These windows, hinged at the side, were common in the 16th and 17th centuries.

The introduction of sash windows in the late 17th century significantly influenced window design in England, particularly in London. While the exact origins of the sash window are debated, it is often attributed to Dutch influence. 

In England, the design gained popularity through architects like Sir Christopher Wren, who used sash windows in prominent buildings such as Hampton Court Palace and parts of St. Paul’s Cathedral. 

Over time, sash windows became a defining feature of London homes, known for their elegance and functionality.

The rise of sash windows also coincided with the reconstruction efforts after the Great Fire of London in 1666, offering a more refined aesthetic that fit the grandeur of the new buildings.

Why Sash Windows? The Unique Aesthetic of London Streets

Sash windows were more than just functional—they symbolised wealth, elegance, and status. British sash windows were designed to complement the tall, high-ceilinged rooms of the affluent.

Their vertical design worked particularly well in these grand properties, allowing for larger panes of glass that brought in an abundance of natural light into the interior of homes —an essential feature in London’s often grey climate. This made sash windows both a practical and aesthetically pleasing choice for the city’s elite.

They allowed architects to create beautiful, elongated frames that were both practical and visually striking. You could even gauge the age of a building by the sash window design, with older windows showcasing the entire frame while newer constructions often concealed parts of the window behind the brickwork – a requirement after the great fire of London. 

Over time, the sash window became a hallmark of British architecture, particularly in London. Whether it was a grand estate or a modest Victorian railway house, sash windows were everywhere, adding character and elegance to homes.

Victorian and Edwardian Innovations: The Peak and Eventual Demise

The evolution of window design continued into the Victorian and Edwardian eras. Advances in glass-making technology allowed for larger panes of glass, reducing the need for multiple panes separated by wooden glazing bars called muntins. This transition is evident in the transformation from small, divided panes to larger ones with a single glazing bar. 

The Edwardian period saw the introduction of bay windows, which further enhanced the aesthetic appeal of London homes, allowing for even more light to flood the interiors while adding architectural complexity to the exterior.

In the 1930s to 1950s, replicating the craftsmanship of original sash windows became increasingly difficult while maintaining competitive pricing. As demand grew, joiners began turning to machinery to speed up production.

However, in doing so, the quality of craftsmanship suffered, as shortcuts were taken to save time and reduce costs. Traditional techniques that had once ensured precision and durability were often abandoned, leading to a noticeable decline in the overall quality of sash windows during this period.

As a result, the general public grew frustrated with poor quality wooden windows made with substandard materials because it meant they had to be maintained more frequently than even their original sash windows.

Modern Challenges: The Rise of uPVC

By the mid-20th century, the introduction of uPVC windows marked a significant turning point in window design and maintenance. Their popularity can be attributed to their low maintenance requirements—many homeowners were weary of the constant repainting needed for timber windows—and their affordability. 

In fact, uPVC windows could cost as little as half that of traditional timber options, earning them the nickname “white gold” among sellers, thanks to their self-sustaining demand.

This transition marked a decline in the use of traditional timber windows, particularly outside of conservation areas, as today, a significant majority of windows in non-historical areas of London are made from uPVC (plastic), due to its affordability and low maintenance requirements.

However, uPVC windows come with their own set of challenges. In the late 1990s, it became clear that this so-called “white gold” didn’t live up to its long-lasting promises. Over time, uPVC windows began to lose their colour, develop mould, and warp due to swelling and shrinking, often leading to cracks or malfunctions. 

Unlike traditional wooden windows, uPVC couldn’t be repaired or restored, meaning once they failed, they had to be completely replaced, with many ultimately ending up in landfills.

In contrast, timber windows and doors made with the correct materials and joinery processes can be restored, sanded, and repainted, making them a more sustainable option in the long run.

Timber Renaissance: Merging Tradition with Innovation

For companies like Todi & Boys, the challenge has been to merge the timeless beauty of timber sash windows with modern technology to create products that are both beautiful and functional. 

Over the years, significant advancements in both materials and craftsmanship have transformed sash window production. 

Initially, sash windows were crafted from high-quality, mature softwoods sourced from European forests. These timbers were dense and durable, providing excellent performance for decades.

However, as European forests became protected or depleted, timber merchants began sourcing younger, less mature softwoods from further afield. Unlike the original materials, this “new age” softwood was far less dense, leading to significant issues such as increased swelling, shrinking, cracking, and rotting in the UK’s variable climate. As a result, maintaining these windows became far more labour-intensive, with upkeep needs rising dramatically in some cases.

Joineries then turned to hardwoods like Meranti from the Far East, which proved problematic; despite its classification as a hardwood, it was still prone to rot and deterioration over time.

Sapele, a dense hardwood from the Mahogany family, has become a popular choice for those seeking high-quality sash windows due to its durability. However, its performance is significantly enhanced through lamination and reverse-grain glueing processes. 

These techniques effectively remove the natural tension within the wood, preventing issues like warping or bowing over time. Todi & Boys apply these processes, helping Sapele offer both strength and stability, making it an ideal material for long-lasting, high-quality sash windows.

Additionally, the introduction of modern alternatives, such as Accoya wood, has since revolutionised the industry, offering superior durability and resistance to the harsh British weather, ensuring long-lasting performance.

Accoya, introduced in the 2000s, is a groundbreaking timber that undergoes a process called acetylation. This process utilises the naturally occurring vinegar in the wood to block the absorption of moisture, significantly enhancing its resistance to water, rot, and insect damage. 

As a result, Accoya is highly stable and less prone to deterioration, with a guaranteed lifespan of up to 50 years above ground. This exceptional durability makes Accoya a trusted choice for homeowners and builders seeking long-lasting performance in their sash windows.

Its stability and resilience ensure that sash windows crafted from Accoya can withstand the challenges of the unpredictable British climate while retaining their classic aesthetic appeal for decades.

Technological Advancements & The Future of Window Design

In addition to advancements in materials, glazing technology has played a significant role in the evolution of window design. Modern sash windows now incorporate double glazing filled with argon or krypton glass in heritage units, which vastly improves insulation and energy efficiency. 

The glass is sealed with high-performance sealant that turns to rubber when cured, preventing condensation—a common issue with earlier double glazing methods. These innovations mean that today’s sash windows perform better than their modern counterparts in terms of thermal efficiency while maintaining their historical charm.

The craftsmanship behind sash windows has also seen a resurgence. While mass production in the mid-20th century led to a decline in quality, modern tools and machinery jointly engineered across European countries like Britain, Italy and Czechia have brought back the precision and attention to detail that was once a hallmark of window making in London. 

Todi & Boys, for example, has heavily invested in new machinery that allows for incredibly precise joints and a flawless paint finish, giving the windows a perfect balance of elegant tradition and innovation – leading to that wow factor that’s sought after by builders, architects and home renovators in London. 

Looking forwards, the future of sash windows is bright, with new technological advancements such as vacuum glazing currently undergoing research and development. Unlike conventional double glazing, which uses air or inert gas between glass layers for insulation, vacuum glazing features a thin vacuum space between two panes of toughened glass. 

This ultra-thin vacuum layer, just 0.2mm thick, drastically reduces the transfer of heat and sound, making vacuum glazing a promising future solution for enhanced energy efficiency and noise reduction in sash windows.

Whilst current double glazing is between 20-28mm thick, this new vacuum glazing is only 8mm thick. Taking us back to the traditional single glazed looking windows but with drastically better security, thermal efficiency and longevity.

Blending Heritage and Modernity: The Todi & Boys Approach

At the heart of Todi & Boys’ philosophy is the belief that windows are not just functional elements but key contributors to a home’s character. Their approach blends the heritage of traditional sash window design with the latest advancements in technology and craftsmanship. This is reflected in every single window that they make. 

Energy efficiency and sustainability are also key concerns in modern window design. Todi & Boys are committed to creating sash windows that meet the highest energy performance standards while maintaining the aesthetic integrity of historical homes. Both of which are key contributors to a home’s resale value.

Todi & Boys understand that a window is more than just a frame—it’s a connection to London’s architectural past, a blend of elegance, history, and modern innovation. They work hard with a single vision, when someone walks past your home, they’ll look at it and think “wow, they have the nicest windows on the street” 

A Summary

The evolution of sash windows in London reflects the city’s ability to marry heritage with innovation. From the grandeur of the early sash windows to today’s high-tech, energy-efficient designs, windows have always been a focal point of London homes. 

Companies like Todi & Boys are at the forefront of this movement, creating timber windows that respect tradition while embracing the future. Through advancements in timber, glazing, and craftsmanship, they ensure that London’s iconic sash windows will continue to be a symbol of beauty and quality for generations to come.