New Steel Framed Glazing Takes Pride of Place in London Conservation Area

Updating or altering a building located within a Conservation Area requires the owner to apply for permission and securing this can be a lengthy process. Therefore, it is prudent to start discussions with the planning authority or to involve a conservation architect or heritage consultant as early in the process as possible. Ultimately, what these specialists will be aiming to achieve is the retention of the specific character of the building involved with reference to its style, the time period it was designed and constructed in, and the surrounding area.

Replacing steel windows in a Conservation Area may be necessary because the existing windows have deteriorated due to age or neglect and are no longer fit for purpose, or because there is a need to reduce the energy loss from the original frames.  New steel windows are also required when an extension is added to a building and the new fenestration needs to match the rest of the windows and doors and to replace inappropriate plastic windows that were installed at an earlier, less regulated time.

We tend to think of steel windows as belonging to the mid-twentieth century.  However, before the introduction of standardised rolled steel window sections at the end of the First World War, steel windows were already popular in domestic architecture, particularly as a result of the fashion for leaded light windows in the late nineteenth and first half of the twentieth century.

Today, the steel window replacement industry remains dominated by hot rolled steel windows whose profiles are close in appearance to those which have existed in a similar form for around 150 years. The look of a mild steel frame has not really changed since late Victorian times and the basic ‘Z’ pattern section used to create both fixed and opening lights remains universal.

There are fewer profiles available today and steel windows do vary significantly, but new steel profiles can - at high cost - be rolled to order to replicate even rare and unusual examples of historic fenestration.

Modern steel frames are hot dip galvanised to EN ISO BS:1461:2022, weather stripped and have a surface coating of polyester powder paint to BS 6497 2005 EN 13438 2018 applied.  Subject to the historic significance of the property Conservation Officers will insist on single glazed replicas, but it is possible to produce double glazed insulated glass units which are very close to the look of a traditional steel window.  These double glazed units will achieve energy preservation, security, reduction of sound and solar gain without detracting from the building’s appearance.

Hampstead Garden Suburb in London was designated a Conservation Area in 1968.  Internationally recognised as one of the finest examples of early twentieth century domestic architecture and town planning, the Suburb was conceived by Henrietta Barnett in the early years of the 1900s as a model community of beautiful houses set in a verdant landscape and the properties within it were designed by some of the best architects of the day.

Today the Suburb comprises around 5,000 properties and is home to some 16,000 people. The Hampstead Garden Suburb Trust operates a management scheme which requires freeholders to get prior approval before altering the external appearance of their properties.  This means that the Suburb today survives relatively intact and still reflects the original vision of Barnett and master planner Raymond Unwin.

A good number of the properties in the Suburb have original steel framed windows and the Trust stipulates that replacement windows must be very similar to the originals. Clement Windows Group has two main window ranges which are suitable for these properties – Brooking, which was developed in conjunction with the Trust and other conservation bodies and takes is name from internationally renowned collector architectural historian Charles Brooking, and EB20, an exceptionally slender, high specification steel window which replicates existing or original steel windows.  Clement’s W20 steel profiles are also appropriate for replacement steel doors in this Conservation Area.

The stunning Arts and Crafts style house pictured in the images above and the one below is located in Hampstead Garden Suburb and has recently been fitted with new leaded Brooking windows and W20 steel doors, providing a great example of how similar to the original fenestration new replacement steel frames can be.  The front and back elevations are very different and yet the new windows provide just the look that the owner and the Hampstead Garden Suburb Trust were seeking without detracting from the character of the property.  The new windows and doors are expertly engineered, high performance, double glazed units with krypton gas filled making them more thermally efficient and the exceptionally slim frames allow the maximum amount of light to flood the interior.  Both the windows and the doors were polyester powder painted RAL 9005 Jet Black.

Properties in the Suburb differ in style and the owners of this early nineteenth century home in the Suburb (below) also chose Clement to carefully recreate the existing cottage pane style windows and doors of their property.
The Brooking range with genuine T bars and classic Fenestra joints was used for the windows and the doors were manufactured from W20 steel profiles. All the frames were painted RAL916 Traffic White with the handles to match.

Finally, the owner of this beautiful home, which is also influenced by the Arts and Crafts movement and located in the Hampstead Garden Suburb, recently opted to replace the original windows and doors which were draughty and no longer fit for purpose.

The Clement range of Brooking windows, which feature a specialist ‘putty fronted’ system, was chosen together with doors from the Clement W20 range, to match the original fenestration perfectly.

The new, bespoke steel doors and windows were painted dual colour - RAL 9005 (Jet Black) on the outside to replicate what was there originally and RAL 9016 (Traffic White) on the inside to complement the interior design.

In each of these cases, all work was carried out with the approval of Barnet Planning Department and the Hampstead Garden Suburb Trust.

Clement Windows Group manufactures an innovative range of steel windows, steel doors and steel screens for both private residences and commercial projects.  Based just outside London, in Surrey, Clement also supplies conservation rooflights, available from stock or made bespoke to individual requirements, in either a tile or a slate profile.

Tel: 01428 643393    Email:    Web:


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