The refurbishment of the Regent Place Hotel in London, originally built in 1915, has been described as a textbook example of recycling an old steel frame.
The project demonstrates the versatility, adaptability and sustainability of steel construction.
It won one of four prestigious Structural Steel Design Awards this year, as well as various construction and property accolades and a BREEAM ‘Excellent’ Rating, which celebrates the development’s green credentials.
Now known as Air W1, the project, for The Crown Estate, is a collaboration between architect Dixon Jones, structural engineer Waterman Group, steelwork contractor William Hare Ltd and main contractor Sir Robert McAlpine Ltd.
Once the largest hotel in Europe, boasting 1,100 rooms, the redevelopment gutted the shell and retained the original Grade II listed façade. Now the building houses seven floors of offices, retail shops at ground level, restaurants in the third level basement and nine apartments.
Over 1,000 tonnes of existing steelwork, including massive plate girders, have been carefully assessed and then refurbished, adapted or enhanced behind the Edwardian façade. Where it was not possible to use the existing structural elements, the steel was removed, sent for recycling and replaced with new elements. The end result is a seamless blend of the old and the new.
Engineering firm Waterman arranged for test samples to be cut from elements of the existing structure in order to verify properties of the material. These results were then passed to William Hare for incorporation into the final connection design.
One of the more unusual uses of the existing steel structure was to support one of the tower cranes, which was welded to it. This was done to protect the still partially intact 1930s art deco Atlantic Bar while disassembly took place.
Structurally, the building features a larger floor plate than is usual for a project of this type. This was facilitated by some large plate girder transfer structures at the lower levels. In total it features about a dozen large plate girders each weighing over 10 tons with the largest being 3.2 metres deep.
Where these plate girders exceeded the capacity of the tower cranes, additional splices were introduced to break the members down into smaller pieces. These were held in place by temporary propping steel until fully erected.
To protect health and safety on site, work at height was minimised. The building’s six atrium bridges were delivered to site as a prefabricated unit and all edge protection, decking, reinforcement and edging fitted at ground level prior to installation.
The roof structure also posed challenges. The complex geometry of the mansard/atrium roof placed the spotlight on fabrication accuracy and management of the delivery and erection sequence so as to ensure that the construction process could proceed without a hitch.
In addition, as it was not possible to survey the roof connections until late in the project timetable, the final connection design and fabrication in some cases was actually competed on site.
The layout of the new slabs against the retained façades also put constraints on the sizes of the members used, and this resulted in the provision of stiff fabricated boxed sections around 200 millimetres deep.
Communication was essential to the success of the project. Following a specially established protocol developed by main contractor Sir Robert McAlpine, William Hare and the M&E contractor were able to report zero clashes occurring between the service holes in the beams and the M&E plant – an almost unprecedented result for a project of this size and complexity.
Two combined cooling heat and power units, photovoltaic cells and thermal stores provide 22 per cent of the energy and heat for both this building and the adjacent Café Royal. One of these units is said to be the largest and most efficient fuel cell in Europe, reducing carbon dioxide emissions by 40 per cent.
Work on Air W1 began in 2008 and continued through the recession. The go-ahead was given at a time when most schemes were being pulled. When the building finally opened, it was both ahead of time and under budget and the developers were rewarded by a lack of competition from alternative schemes.