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Steel windows and architecture

Ask most people in the United Kingdom about steel windows and they will talk about the ubiquitous, mass-produced standard metal window.

A much smaller number will mention the use of the universal casement windows in the inspirational designs created by the world’s foremost architects.

Even fewer will talk of the architectural movements which were made possible because of the essential characteristics of steel windows.

My love affair with steel windows and a dislike of inappropriate refurbishment, started very early in life. I was brought up in a row of imposing, large, Victorian semi detached houses, in a North Western town.

At the end of the row, the local coal merchant had built himself an art deco villa, with flat roof, white rendered walls, and sweeping curved corners.

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Eventually I went away to university, and started working in London. Then, on a visit home, I was horrified to find that it had been split into two houses, and the new owners had modernized it. One half of the flat roof was now pitched, the render on the other half had been replaced by pebbledash, and, worst of all, the curved steel windows had been replaced by facetted plastic. 




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Crittall windows

Just like ‘biro’ and ‘Hoover’, Crittall has become the generic term for steel windows. So how did a blacksmith’s shop in a small market town in North Essex become the world leader in window manufacture, with manufacturing plants on five continents?

Metal windows had been used since Tudor times. The Elizabethan casement glazed with leaded lights was an architectural feature unique to Britain. Glass was so expensive in Britain that people took great care to ensure that the frames were strong. They were very popular as nearly every village had a skilled blacksmith who could manufacture them, but very few had skilled joiners to provide an alternative in timber.

With the advent of Palladio and Wren’s architectural styles, coupled with improvements in the glass manufacturing process, the fashion for larger, more dignified house building, with correspondingly larger windows, grew. The double-hung wooden sash window became the window of choice for the discerning homeowner.
However, there was some dissatisfaction with timber sash windows. Complaints ranged from broken sash cords, warped sashes, and sticking, shrinking or rattling.

Crittall began by manufacturing metal windows for agricultural buildings and churches, using wrought iron, bronze, and increasingly mild steel. With the attitude that epitomizes the spirit of the Victorian age, Francis Henry Crittall, with his team of skilled craftsmen, set out to develop an engineered window, made of metal, which would overcome all of the problems of the wooden sash.

A number of other companies around the country were manufacturing metal windows: Wragge’s of Manchester were the pioneers, they were soon joined by Wenham & Walters, Williams & Williams, Hopes, and Burt & Potts.

Improvements in machine tools allowed the first change made to the design, which was the introduction of rudimentary dovetail joints for corners rather than brazing, which resulted in a considerably stronger and more reliable product than before.

Despite the improvements in the steel windows, they were not readily accepted in the residential market. However, in other sectors, the new windows were extremely popular. Projects included the National Gallery, Harrow School, the Royal College of Music, and the Public Records Office.

The next major development in the design of steel windows was the fenestra joint by Crittall, which, because of its strength, allowed slimmer glazing bars, and therefore more daylight through the windows.

In 1909, following rationalisation work carried out by Walter “Pink” Crittall, the Universal Ranges of steel sections were launched which allowed improvements in the manufacturing process, with the result that consistent manufacture of steel windows could be achieved by semi-skilled workers, rather than skilled craftsmen as previously.

Further innovations followed, including the welding of corners, hydraulic straightening of bars, and a dual strike plate for handles to allow night-time ventilation with no loss of security.

This all resulted in a better performing window, at a lower cost. However, the universal casement window was still a luxury product at a premium price.

The First World War proved to be a turning point for the steel windows industry. Factories were turned over to the manufacture of munitions and many lessons were learnt which would be adopted in the immediate post war era.

At the time, steel windows were still more expensive than their timber counterparts.

This was about to change.

Productivity improvement as a result of standardisation was the first lesson put into practice. Crittall’s closest rival, Henry Hope, proposed the adoption of a standard design, to help the steel window industry compete to supply windows for the 200,000 new homes promised to be built by the UK government in 1919.

A new, light, profile was designed to act as a mullion which would allow composite units to be built. Following long discussions with architects, standard units were designed, which matched the current brick sizes, and suited the height of the modern room.

The first project which used these ‘cottage windows’ was for the Admiralty in Chepstow. A typical window was sold for £1.95 including fittings which was a few pennies cheaper than the equivalent timber window without fittings. Further work was carried out for Bristol Corporation, which had a massive building programme for the post war years. The increased volume saw even further cost reductions.

In 1920, following much canvassing by Valentine Crittall (later Lord Braintree), the Ministry of Health, which was at that time responsible for government housing specifications, agreed to include the standard cottage window in its plans for housing schemes. From then on, it was used in almost every housing scheme throughout Britain up until the 1980s.

The success of the steel window is due, in no small part, to the continuous improvement in product and manufacturing processes. 

Innovations included the development of a comprehensive range of standard metal windows,   Zincspra and subsequently hot-dipped galvanizing to protect the steel frames, then Duralife polyester powder coating, to provide an enameled finish to the windows.

Performance improvements have been achieved by modifying profiles to incorporate double glazed units and improved weatherproofing.

Today, the steel window is no longer a high volume product in mass production. As a result, there are cheaper alternatives available. But you do get what you pay for.

Today, homeowner decisions on refurbishment take into account energy performance and sustainability of the materials used.

The thermal performance of the modern replica steel window has been tested and proven to be 400% more efficient than the original single-glazed window.

Another environmental benefit of steel windows is that steel is the most recycled material in the world (source:  The mild steel which goes to make today’s steel window frames contains 98% recycled material.

In North America, the steel window is seen much more as an aspirational product, as can be seen by the images and comments at this popular North American interior design blog, appropriately named Things That Inspire.  Crittall Windows’ North American residential customer list reads like a Who’s Who of successful businessmen, politicians, and entertainers.

Crittall Windows are so successful in North America that in April this year, it was announced that they had won the coveted Queens Award for Enterprise in International Markets. This British-owned independent company, the largest supplier of steel windows in Europe, is now the No 2 supplier of steel windows to the North American market, having built a distribution network from scratch following a management by out in 2004.

John Keleher is the IT Manager of Crittall Windows, where he has worked since 1994.  John’s previous position was manufacturing systems manager for the engineering division of VSEL (now part of BAE), the company that built the Trident nuclear submarine fleet and Trafalgar Class hunter-killer submarines among other armaments.   John can be followed on Twitter at @johnkatcrittall

For more information on steel windows, please contact Crittall Windows on +44 (0) 1376 530800 or visit
Crittall Windows is a member of ProjectBook, which has been created to help owners of listed or period properties understand how their buildings work and to help them find appropriate craftsmen, products and specialist information. The online Heritage Register contains over 540 registered businesses, the largest directory of its type in the UK. For more information, visit


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