Winding steel ribbons form the striking exterior of the 12-storey W Edinburgh. The bold design by Jestico + Whiles adds a contemporary twist to the skyline of the historic city. The round-shaped building complements St James Quarter, one of the most significant city centre transformations underway in the U.K. A new quarter of the city, it completes the Edinburgh’s distinctive offer with a stunning new shopping galleria with over 80 new brands, an enticing mix of restaurant and bars, a boutique Everyman Cinema, a Roomzzz Aparthotel, an enviable events programme in a range of new and attractive public spaces and, of course, the luxury W Edinburgh. Octatube has realised the eye-catching stainless-steel facade of this landmark building.
The steel ribbon breaks out of the ground of the square and seems to slowly wrap itself up around the building. It forms the balustrade of the higher floors. On top of the building, the ribbon winds gracefully in an aesthetically free form upwards in a point. The ribbon is made of Rimex steel: 2 mm thick stainless steel of which the colours and tones vary in different lighting conditions. This is known as metamerism: a ‘living’ colour when viewed from different angles.
Engineering a complex geometry
Because of its curves, the ribbon has a complex and challenging geometry. Octatube has invested in creating and testing innovative technical and structural solutions. Thanks to our customized software (based on Grasshopper and Inventor) we were able to design the structure in detail. As a result, it meets all structural requirements and fits perfectly on the main building structure. With this model, we not only aesthetically optimised the divisions between the Rimex panels, we optimised the panel sizes and the underlying steel structure as well. Together with meticulous control on material use, this resulted in very little waste. We scripted every part of the ribbon in a very efficient and generic method.
The ribbon forms the balustrades of nine floors that, due to the unique shape of the building, have different floor plans. For example, the balustrades on some floors slope slightly outwards, while on other floors they slope inwards. On the outside of the balustrade we placed Rimex-panels, segmented in order to follow the curves of the building. The panels are attached by folding and hanging them on little hooks on the underlying steel structure. On the inside of the balustrade we placed powder coated aluminum panels. On some floors the balustrades have a continuous curved stainless-steel handrail.
Some of the balustrades required innovative detailing at the points where the Rimex-panels curve down to make room for glass infill panels. We did several variant studies to choose the best detailing. In the end we designed a complex Rimex curve bonded to an aluminum substructure and secured with rivets. This structure has minimal joints and could only be achieved with high level craftmanship.
High quality mock-up
At Octatube, we love working with mock-ups. It is often the first real encounter with the new building, and it illustrates the result of choices in material and detailing. A mock-up shows us what works and what does not, and thus provides valuable information and insights for the assembly. We made a 7 metre mock-up of the balustrade that allowed us to prove consistent quality and ensure that the structure met all performance requirements giving confidence to us and our client.
Torsion in plating
Other parts of the ribbon that Octatube realised are the so-called lower ribbon - the part that winds up from the square towards the building - and the top flourish - the 17-metre-high section on the roof that curls into the air. These separate structures presented completely new challenges.
Where the Rimex-panels in the balustrades are flat, there is torsion up to 15 cm in the plating of the lower ribbon and top flourish. This torsion in the Rimex-panels had to be extensively tested. We made a prototype of the part of the top flourish that has the most torsion. We used wood instead of steel to quickly build the main structure of this prototype and added all the bespoke detailing to see if and how they would work.
One of the details and challenges we tested was the fixing of the side panels: we attached them to the main steel structure using screws. By folding the panels in such a way, the next panel covers the screws. This creates a visually aesthetic joint of 7 mm and keeps the screws out of sight. But with 150 segments in the top flourish, we had to be sure that in case of damage to one panel, we would not have to dismantle the entire structure. After a successful test, we shipped the prototype to Edinburgh to show it to our client as well as our assembly crew on site.
The roof of the building serves as an outdoor terrace for parties and events. The terrace is equipped with nine elliptical roof lights: eight small ones (2,7x1,9 m) and one large one (4,6x3,6 m). Of course, we calculated and tested these roof lights in such a way that they can be used for dancing, specifically dancing in high heels. For this reason, we also provided them with a very durable anti-slip etching. The large roof light consists of two glass panels with a 310 mm high structural glass fin as support.
The parametric design and testing with mock-ups and prototypes saved us a lot of time and also material. Of course, this way of working also provides a lot of extra knowledge that we can use in future projects.
Laing ‘O Rourke | Jestico + Whiles | Aldowa | CSM