• 2 September 2026|
• News|
• Daniel Anderson

If you’ve been researching steel windows for a period renovation or a new-build project, you’ve almost certainly come across the name Crittall. But what is a Crittall window, exactly, and why do architects and homeowners keep specifying them nearly a century after they first appeared?

This guide covers everything a first-time buyer needs to know: the history, the construction, how to spot the genuine article, and where these windows work best. We’ll also walk through the range available from Metwin, so you can find the right fit for your project.

What is a Crittall window?

A Crittall window is a steel-framed window known for its slim sightlines, strong industrial look and distinctive glazing bars. The term comes from Crittall Windows Ltd, the company that pioneered steel window frames and turned them into one of the most recognisable features of British architecture.

The key characteristics are:

Steel frames: Steel is far stronger than timber or aluminium of the same thickness, so the frames can be much slimmer while still holding the glass securely.

Slim sightlines: Because the frames don’t need to be bulky, more of the window is glass. This gives a clean, uninterrupted view and lets in more natural light.

A grid of small panes: Traditional Crittall-style windows are divided into multiple panes of glass by narrow glazing bars, creating the classic industrial look associated with factories, warehouses and Art Deco buildings.

Durability: Properly maintained steel windows can last decades, which is part of why so many original examples are still in use today.

A brief history

The story starts in 1849, when Francis Berrington Crittall bought an ironmonger’s shop on Bank Street in Braintree, Essex. After Francis died, the business passed briefly to his son Richard before going to his second son, Francis Henry Crittall, in 1884.

Francis Henry Crittall saw the potential of steel and began manufacturing windows with much slimmer frames than the timber alternatives of the day, effectively pioneering the steel window as a product in its own right. Demand grew quickly, and by the 1920s the firm was mass-producing standard-size steel windows for the booming modernist movement, appearing on factories, offices and homes across the country.

Steel window frames became closely associated with the Art Deco and modernist movements of the 1920s and 1930s, and the “Crittall” name became so widely used that it’s now often treated as a general term for this style of window, in the same way “Hoover” is used for vacuum cleaners.

Genuine Crittall products vs steel-look imitations

Here’s where buyers need to be careful. “Crittall” is a registered trademark, and Crittall Windows Ltd is the original manufacturer. However, because the style has become so popular in recent years, the market has filled up with steel-look aluminium windows designed to imitate it.

These imitations use aluminium frames with a black finish and applied glazing bars to mimic the appearance of genuine steel windows, but they aren’t the same product. Here’s why the distinction matters:

• Material – Genuine steel frames are structurally different from aluminium. Steel’s strength is what allows the sightlines to be so narrow in the first place.
• Sightlines – Aluminium imitations generally need thicker frames to achieve the same strength, so the sightlines are rarely as slim as genuine steel.
• Longevity – Well-made steel windows, properly galvanised and finished, are built to last. Cheaper aluminium look-alikes can vary enormously in quality.
• Conservation compliance – For listed buildings and conservation areas, planning officers often specifically require genuine steel windows rather than aluminium substitutes.

If you’re planning a significant investment in new windows, it’s worth checking exactly what material and construction you’re being quoted for. A low price on a “Crittall-style” window is sometimes a sign of poor quality materials rather than a good deal.

Where Crittall-style windows work well

Steel windows suit a wide variety of properties, from genuine period restorations to entirely new builds:

• Period and listed properties – Original steel windows are common in properties from the 1920s–1950s, and matching replacements are often needed to satisfy conservation area requirements.
• Wraparound extensions – The slim frames and large panes of glass make steel windows a popular choice for glazed extensions and orangeries that need to maximise light.
• Contemporary new builds – Many architects specify steel-framed windows and doors purely for their aesthetic appeal, pairing the industrial look with modern interiors.
• Room dividers and internal screens – The same slim-framed style is increasingly used indoors, to create partitions that let light pass between rooms without a solid wall.

The Metwin range

Metwin supplies steel windows for a wide range of applications, from full external replacements to internal screens and one-off bespoke designs. Here’s how the range breaks down.

External windows

For facades, extensions and full window replacements, external steel windows need to cope with the weather while still delivering the slim Crittall look. Metwin’s external systems include:

• Corporate W20 – the original, classic profile, with narrow 20mm sightlines that maximise the glazed area and keep the frame as unobtrusive as possible. It’s the traditional choice for conservation projects where an authentic historic appearance matters most
• W20 TE (Thermally Efficient) – the same slim, classic profile re-engineered for modern energy performance, with a U-value of 1.4 W/m²K, dual weather seals, and compatibility with double glazing up to 24mm.
• Homelight – built specifically for residential replacement and refurbishment projects, combining the traditional slim aesthetic with strong thermal performance. As standard, it includes double weatherstripping, double glazing, hot-dip galvanising and multipoint locking
• SMW and SMW+ – ideal for heritage contexts, these windows are single glazed (SMW) or double glazed (SMW+) with 12mm heritage units. Offered solely by our team at Metwin, these windows are typically used within conservation areas, Listed buildings and other properties of national or historic interest.

Interior windows and room dividers

The same slim steel profiles used on external windows also work well indoors. Interior steel screens and room dividers let light pass between rooms while creating a visual break between spaces, without the bulk of a stud wall. These are increasingly popular in open-plan homes and commercial fit-outs, where the industrial look of a Crittall-style screen is used as a deliberate design feature rather than a structural necessity. Because they aren’t exposed to the weather, interior screens can focus purely on sightlines and finish, without the same thermal considerations as external windows.

Bespoke windows

Not every project fits a standard profile. Metwin also produces bespoke steel windows and doors made to measure for specific architectural briefs – arched or curved openings, oversized glazing, non-standard pane layouts, or matching an existing historic window on a listed building. Bespoke work draws on the same Corporate W20, W20 TE and Homelight systems, adapted to the exact dimensions and detailing a project calls for. This type of window allows for complete design freedom, as our bespoke windows can be made in a variety of shapes and sizes.

Key takeaways

• A Crittall window is a steel-framed window with slim sightlines, known for its industrial and Art Deco heritage.
• The name comes from Crittall Windows Ltd, founded by the Crittall family in Braintree, Essex.
• Genuine steel windows differ from aluminium “steel-look” imitations in material, sightlines and longevity.
• Steel windows suit period restorations, wraparound extensions, and contemporary new builds alike.
• Metwin supplies external windows (Corporate W20, W20 TE, and Homelight), interior screens and room dividers, and bespoke steel windows made to measure.

Frequently asked questions

What is a Crittall window used for?

Crittall metal windows can be used anywhere a slim, strong window frame is wanted – period properties, conservation area renovations, glazed extensions, and contemporary architectural projects where large areas of glass are a priority. As replacement windows, Crittall windows can offer improved thermal efficiency and durability whilst retaining the classic Crittall style that has made these frames so iconic.

What are Crittall windows made from?

Crittall windows are made from high-quality steel, which gives them their iconic slender frames, exceptional strength, and distinctive appearance.

Are all steel windows genuine Crittall products?

No. “Crittall” is a registered trademark. Many products on the market are steel-look aluminium windows designed to copy the appearance, but they aren’t manufactured the same way. Standard metal windows won’t necessarily have the same quality that the famous Crittall name is known for.

Do steel windows meet modern building regulations?

Yes, when specified correctly. Ranges such as W20 TE are designed to comply with Approved Document L and offer significantly better thermal performance than older, uninsulated steel windows.

Can steel windows be used in conservation areas?

Often, yes – and in many cases they’re required, since planning officers frequently specify genuine steel frames to preserve the character of listed buildings and conservation areas.

Get in touch with Metwin for premium Crittall windows

Whether you’re restoring a period property or planning a new glazed extension, our team can help you choose the right steel window system for your project.

Get in touch with Metwin today for a free quote, or to discuss your project in more detail:

• Fill in our online contact form
• Call us on 0208 523 2081
• Email enquiries@metwin.co.uk