The Importance of Numbering in Refurbishing Big Ben Clock Tower

In a recent Autodesk University presentation, the use of building information modeling (BIM) and Autodesk Revit was highlighted on the high-profile seven-year project to refurbish Big Ben (aka. Elizabeth Tower), the world’s most famous clock tower and the centerpiece of the UK Parliament.

Started in 2015, the project was undertaken by Purcell Architects, Heritage Consultants and Masterplanners. In addition to Revit, Purcell used PowerPack for Revit, as described by Purcell project lead Andrew Dobson during his Autodesk University 2022 session.

Dobson explained Purcell has been using BIM since 2006 and that the company utilized BIM to develop its historic building information management protocol. The HBIM protocol has transformed Purcell’s approach to documenting and designing conservation, repair and creative adaptation of historic buildings. Revit has been used by the company for new builds and adapted for historic building repair, particularly the approach taken to repair and refurbish Big Ben.

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Described on the Purcell website in 2020, the project was the most complete restoration of Big Ben in the Parliament building’s history. It addressed corrosion of the 160-year-old cast iron, with 10-20% of the iron work needing to be replaced. Also included were restoration of the building’s external fabric, renovation of the clock, improvements to internal areas, addition of energy efficient lighting, and installation of a new elevator.

Dobson explained that refurbishment of the cast iron roof promised to be a painstaking process. Each one of the cast iron tiles had to be removed, numbered, restored, then replaced in its original location.

The photograph above shows the white numbering (tag) on each tile. The tiles had to be tracked by number and replaced in the exact same location because each tile is unique, like a puzzle piece.

After removal, each tile had a brass tag affixed which would survive the sand blasting process. Each component was tracked and put back into the correct place after refurbishment. The numbering process was made immensely more manageable using the Numbering Tool in PowerPack for Revit.   

The stone and iron repair work involved a lot of detail, which Dobson said aligned well with BIM. Previous refurbishments were performed in the 1930s, 1950s and 1980s, but this was the first time Revit was used.

Previously, all the plans, sections and details were numbered with component numbers by hand. Dobson said, “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.”

This time around, the process was updated and improved by panelizing the roof using Revit curtain walling. Then a schedule was produced and exported to Excel using Graitec PowerPack for Revit for further documentation. Dobson said that, using Revit’s Tag All Not Tagged feature on an elevation with several thousand components, it was satisfying to see how much time was saved compared to the manual method of previous refurbishments.  

Dobson related that Purcell made the best use of new technology – including Revit and PowerPack for Revit tools. In addition, the company will use the data gathered and lessons learned to inform future work repairing the rest of the Parliament Estate.

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