The Importance of Numbering in Refurbishing Big Ben Clock Tower
During a recent presentation with with Purcell Architects at Autodesk University, the renovation of Big Ben (also known as Elizabeth Tower) was a prime example of how building information modelling (BIM) and Autodesk Revit were utilised throughout the seven-year project.
Big Ben Clock Tower; image: Toby Melville/Reuters
Company: Purcell Architects
Location: London, UK
During a recent presentation at Autodesk University, the renovation of Big Ben (also known as Elizabeth Tower) was showcased as a prime example of how building information modelling (BIM) and Autodesk Revit were utilised throughout the seven-year project. As one of the most well-known clock towers in the world and the centrepiece of the UK Parliament, the refurbishment of Big Ben required precise planning and execution, which was made possible through the innovative use of BIM technology.
Purcell Architects, Heritage Consultants, and Masterplanners initiated the project in 2015. During a session at Autodesk University 2022, Andrew Dobson, the project lead at Purcell, revealed that in addition to Revit, the team utilised PowerPack for Revit to achieve their goals.
During his presentation at Autodesk University, Dobson disclosed that Purcell has been utilising BIM since 2006, and the technology was instrumental in the development of their historic building information management protocol (HBIM). The implementation of HBIM has revolutionised Purcell’s methodology for documenting and designing the conservation, repair, and creative adaptation of historic structures. Revit has been employed by the firm for new construction projects and has been adapted for the repair and renovation of historic buildings, notably in the refurbishment of Big Ben.
Described on the Purcell website in 2020, the project to restore Big Ben was the most comprehensive renovation of the Parliament building’s iconic clock tower to date. The initiative tackled the corrosion affecting the 160-year-old cast iron structure, necessitating the replacement of 10-20% of the ironwork. Additionally, the undertaking involved the restoration of the building’s exterior, refurbishment of the clock mechanism, enhancement of interior spaces, installation of energy-efficient lighting, and the installation of a new elevator system.
During his presentation, Dobson clarified that the renovation of the cast iron roof was an exacting task. The process involved the removal of each cast iron tile, which was then numbered, restored, and finally reinstated in its original location.
Big Ben cast iron roof tiles
Tagged; image: Building Magazine
The image to the right features the white numbering (tag) affixed to every tile. Since each cast iron tile is unique, similar to a puzzle piece, it was crucial to track them by number and reinstate them in their original location.
To ensure the cast iron tiles’ accurate replacement, a brass tag was attached to each one before undergoing sandblasting. Following the refurbishment, every component was tracked and reinstalled in its precise location. The use of the Numbering Tool in PowerPack for Revit significantly streamlined the numbering process.
Dobson noted that the intricate nature of the stone and iron repair work was a good match for BIM technology. While previous renovations took place in the 1930s, 1950s, and 1980s, the use of Revit marked the first time the software had been utilised.
Previously, all the plans, sections, and details were labelled by hand using component numbers. According to Dobson, “There were 3,000 components on this roof. They were manually counted off the AutoCAD drawings and scheduled in Excel, a very time-consuming process.”
For the Big Ben refurbishment, the process was enhanced by utilising Revit curtain walling to panelise the roof. This allowed for the creation of a schedule that could be exported to Excel using Graitec PowerPack for Revit for further documentation. Dobson highlighted the satisfaction he felt using Revit’s Tag All Not Tagged feature, which saved a significant amount of time compared to the manual method used in previous renovations involving several thousand components.
Dobson emphasised that Purcell made the most of innovative technologies, such as Revit and PowerPack for Revit tools. Moreover, the company plans to utilise the data collected and lessons learned to guide future repairs on the rest of the Parliament Estate.
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