W20 steel windows: The 1950s style making a comeback
- September 19, 2026
- Crittall & Aluminium Window Guides
W20 steel windows are a distinctive mid-century profile known for their slim sightlines, strong geometric lines and generous areas of glass. Originally associated with 1950s architecture, the style is now making a comeback in period properties, contemporary extensions and new-build projects.
At Lightfoot Windows, we supply and install genuine Crittall W20 steel windows. With experience dating back to 1935, we understand the characteristics of this heritage profile and how it can be specified for projects where appearance, performance and architectural character all matter.
The history of W20 steel windows
W20 is a classic steel window profile associated with mid-twentieth-century architecture. The strength of steel allows manufacturers to create robust frames with relatively narrow sections, helping to maximise the amount of glass within a window.
Steel windows have a long history across British architecture, appearing in residential, industrial and commercial buildings where their practical construction and clean appearance made them a popular choice.
W20 forms part of this wider development of steel window profiles. Its proportions and detailing give it a distinctive appearance that continues to work in both traditional and contemporary architecture.
For new projects, W20 provides an opportunity to introduce these established characteristics into a new design.
What gives a W20 window its character?
Slim sightlines and square sections
The proportions of W20 are a major part of its appeal. Slim sightlines create narrow frames around the glass, allowing generous areas of glazing while retaining the crisp appearance associated with traditional steel windows.
The flat surfaces and square sections also give the profile its clean geometric character. Used across a series of windows, these proportions can create a strong visual rhythm without making the overall design feel heavy.
This is one reason steel frames continue to appeal to architects and homeowners looking to combine traditional detailing with modern glazing.
T bars and long leg detailing
Traditional steel windows are also recognised by features such as T bars and long leg sections. Details including long leg top and long leg bottom sections can help create the distinctive grid patterns found across traditional steel windows.
Getting these details right can be particularly important when specifying new windows. The pattern and proportions of the design can help new installations sit naturally within the surrounding architecture.
At Lightfoot Windows, we can advise on the configurations available and help identify an arrangement that suits the building and the intended design.
Why is the profile making a comeback?
Renewed interest in mid-century design has encouraged homeowners and architects to look again at traditional steel glazing. There is a particular appeal in retaining architectural character while still meeting the demands of modern living.
The wider steel window market has also benefited from developments in glass technology and manufacturing. Modern systems can incorporate double glazing and improved thermal performance while retaining the slim profiles and geometric appearance associated with traditional steel windows.
This combination makes W20 suitable for a wide range of projects. It can complement the architecture of an older home, add character to a contemporary extension or provide a strong visual feature within a new-build property.
For homeowners and conservation specialists, W20 offers a way to reference the appearance of traditional steel glazing without necessarily accepting the performance limitations of older single-glazed windows.
W20 for new projects
New W20 windows can provide a way to introduce the character and proportions associated with traditional steel glazing. The same approach can work for extensions and new areas of glazing where the new installation needs to complement the surrounding architecture.
For listed buildings and other heritage properties, the appropriate specification will depend on the individual building and any relevant planning or conservation requirements.
At Lightfoot Windows, our service covers advice and site surveys through to specification and installation. We can consider the window pattern, proportions, glazing and finish required for the project.
Whether you are replacing a single window or specifying steel glazing for a larger building, the aim is to create a solution that works with the architecture rather than against it.
Meeting modern requirements without losing the look
Older steel windows were not designed around today’s energy performance requirements. Modern W20 systems can, however, be specified with double glazing and improved thermal performance.
Our Corporate W20 TE system is a thermally enhanced steel window and door system with U-values as low as 1.4 W/m²K. The system is designed to meet Approved Document L while retaining the slim sightlines associated with W20.
This makes it possible to use steel frames in projects where thermal performance is an important consideration without moving away from the appearance of traditional steel glazing.
The W20 TE system can also be used for steel doors and larger glazed configurations, allowing a consistent design language to be carried across different areas of a property.
From windows to internal spaces
Steel glazing does not have to stop at external windows. Internal partitions, doors and glazed screens can divide spaces while allowing natural light to move between rooms.
Glass walls and internal partitions can work particularly well between kitchens and living spaces, home offices and hallways. They provide separation without completely closing off one area from another.
We also supply internal Crittall systems for projects where slim steel profiles and a strong architectural aesthetic are important. These systems can be configured for different applications and grid patterns, helping internal glazing become part of the wider design rather than simply a practical divider.
Finishes, hardware and the finer details
The smaller details can have a significant impact on the finished appearance of a steel window.
W20 systems can be galvanised and finished with polyester powder coating, with a wide choice of RAL, BS and bespoke colours available. This gives projects the flexibility to use a traditional finish or introduce a colour suited to a more contemporary scheme.
Hardware can also be selected to complement the overall design, with different handles and other hardware options available depending on the system and specification.
From the frame itself to the hardware and finish, these details help ensure the completed installation works naturally with its surroundings.
Genuine steel and precision engineering
There is now a wide range of metal windows designed to recreate the appearance of traditional steel using other materials. Aluminium and uPVC can provide alternative solutions, but genuine steel offers its own distinctive characteristics.
At Lightfoot Windows, we supply genuine Crittall W20 systems, retaining the material, proportions and detailing associated with traditional steel glazing. Corporate W20 TE is manufactured from steel and combines slim sightlines with contemporary thermal performance.
For projects where the authenticity of steel is an important part of the design, this provides a way to retain the character of traditional glazing while meeting modern specification requirements.
Supply and installation from Lightfoot Windows
Established in 1935, Lightfoot Windows has decades of experience working with Crittall steel windows and doors. We supply and install genuine Crittall systems for residential, heritage and commercial projects.
Our service covers the project from initial advice and site survey through to specification and installation. We can also advise on internal glazing, steel doors and bespoke solutions where these form part of a wider project.
Our experience allows us to consider the requirements of each property and recommend an appropriate profile, glazing specification, hardware and finish.
W20 steel windows are making a comeback
W20 offers a way to bring the character of traditional steel glazing into period properties, contemporary extensions and new-build homes. Its established proportions, generous glazing and modern specification options make it a versatile choice where both appearance and performance matter.
From rural properties to new commercial spaces, steel windows can provide a distinctive architectural feature while meeting the practical requirements of a modern building.
At Lightfoot Windows, we can help you choose the right Crittall system for your project, from the initial site survey and specification through to installation. Whether you’re specifying W20 for a period property or introducing it into a new space, we can advise on glazing, finishes, hardware and the most suitable system for your project.
Ready to bring the W20 look to your project? Get an estimate from Lightfoot Windows today and speak to our team about your steel window requirements.
