Penny Gowler had to figure out the structure of London’s Grade I listed Midland Bank building before it could be transformed into a new hotel, “The Ned”. The project is shortlisted for The Structural Awards 2017.
Throughout my structural engineering career I’ve worked on numerous buildings, including other London heritage structures like Selfridges in Oxford Street. Much of this experience helped me solve the complex problems that were presented by The Ned. There were three main structural challenges we faced:
First, we had to understand the existing 1920s structure. There were no structural drawings for the original building, so we had to use a combination of intrusive investigation works, materials testing, experience and logic to figure out how the structure worked, and how loads were transferred down to the ground.
BIM (Building Information Modelling) really helped us in this work: we constructed a 3D model from a 2D topographical survey and added information from the limited architectural archive drawings, site investigation works and on-site observations. Information sources were embedded in the model, which evolved as we learnt more about the structure.
We have used this method since, as it allows a great deal of creativity in the re-use or re-appropriation of parts in heritage structures where survey information is limited.
Second, we had to justify the new swimming pool and extension on the roof. We did this by back checking around 100 eleven storey columns and numerous beams, and developing alternative load paths to avoid strengthening columns behind protected Listed finishes.
Thirdly, we had to design a circulation core to accommodate a new London Underground tunnel scheduled to be constructed under the building, co-ordinating with Transport for London. The core is essentially a new building holding lift shafts, additional floor area, and a green roof at the top. It was tied into the original building around its perimeter and interfaced at each level with bespoke details.
Again, BIM helped this work, allowing us to communicate the impact of construction to Transport for London, illustrating the impact works would have on Central and Northern line tube tunnels, and on the new Northern line tunnel planned to run under the hotel in the near future.
Throughout the process we wanted to minimise the interventions and ensure works were carried out as sensitively as possible. There is a lot to like about the original building, including the imposing but elegant Portland stone façades; Lutyens’ spiral staircase - and the circular steel vault door at basement level which was used in the James Bond film Goldfinger
When working with heritage structures like these it’s important to retain as much of the original structure and building fabric as possible to ensure the features are retained and protected for future generations. Justifying an existing structural element for the change in use or loading rather than replacing it, means that much more of the associated finishes can be preserved intact. It’s also much more sustainable to reinvigorate existing buildings rather than demolishing and building something new.
We’re looking forward to taking part in The Structural Awards event, which is a great opportunity to showcase The Ned’s amazing engineering.
Explore The Structural Awards