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Conserving a clocktower in the middle of a working Parliament

The task of conserving the 96m tall tower is a complicated and delicate process. With a footprint of just 12m square and located in the middle of a busy working Parliament, the task is hugely complex.

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In 2017, we started work on the most extensive and complex conservation project in Elizabeth Tower’s history.   

Over the course of six months one of the most complex scaffolds in British history was erected. Scaffolding a Grade 1 listed building which is part of a UNESCO World Heritage site requires extreme care.  

The scaffolding is free-standing in order to avoid any additional load on or further damage to the Tower. The beams and boards were lifted into place one by one and built around the Tower without touching the stonework.  

Damage worse than expected 

With the scaffolding in place, surveyors and engineers assessed and analysed the Tower. Their results fed into the conservation and refurbishment plans developed by a team of heritage experts and architects.  

It soon became clear that the damage to the clock tower was much worse than anticipated.  

Crumbling stonework replaced with hand-carved stone 

Pollution had damaged the soft Anston limestone from Yorkshire, originally used to build the Tower, as well as the Clipsham stone from the Midlands used in later years for repairs. Many of the hundreds of intricate carvings in architect Charles Barry’s design had eroded, as had larger structural pieces of stone.  

To replace the damage, new pieces of stone have been brought in from a quarry near Doncaster in YorkshireOur stonemasons meticulously create a template for each stone before spending at least two weeks hand carving the stone using traditional tools. 

They take multiple trips up the scaffolding, from the workshop at the bottom of the Tower, to ensure the stone is an exact match for the one it is replacing. This ensures the quality of the work matches that of our Victorian forefathers.   

Severe bomb damage to the roof and clock dials 

Bomb damage inflicted on the Tower during the Second World War not only damaged the clock dials and the stonework but also the roof. 

When the roof tiles were removed, it became clear how bad the damage to the cast iron frame underneath was. All 3343 pieces of the roof were removed and transported to an off-site workshop.  

Tiles were blasted to remove old paint before being repaired or replaced if there were significant cracks or other severe damage. The new pieces were cast by hand at a specialist foundry in Halifax to ensure they were a match to the original tiles. 

Over the years, panes of glass in the clock dials had broken and been replaced with poor imitations. The replacement glass didn’t match the original colourAl1296 pieces of glass in the clock dials have been replaced.  

A team of specialist stained-glass experts from South London worked to find the perfect colour match. Pieces of mouth-blown, pot opal glass were cut into shape and then fitted by hand into the frame. Now the visual impact of the dials is true to the original intention of the architects.

Saving the UK’s biggest turret clock 

The Great Clock was the largest and most accurate clock in the world when it was built in 1859 and remains the biggest striking and chiming turret clock in the UK. The complexity of its design, its sheer size and weight, and the complete lack of drawings for the mechanism mean that it habeen an interesting challenge for our clock team.   

For the first time in its history: 

  • the 12-tonne clock has been dismantled, winched 53 metres down to ground level and taken off-site for a complete overhaul
  • each of the hundreds of wheels, pinions and bushes have been examined, repaired, photographed, logged and painted
  • the automatic winding mechanism installed in 1912, parts of which were thought to have been lost, has been rebuilt, and will be put back in place when the Great Clock returns home.  

While the work is undertaken, the hands of the clock are run on an electrical mechanism. In order to ring Big Ben for Remembrance Sunday and New Year’s Eve, a temporary striking mechanism is installed, connected to the clock, and tested before the bell can be struck.  

Modern methods mean better conservation work 

Our engineers and architects are using the latest in digital modelling and virtual reality to design and plan the work. Using diagnostic tools not available to conservation teams in the past, we have uncovered damage to the building that had been previously missed or was undetectable at the time.  

Over the last three years, experts have been able to remedy defects in some of the previous conservation workFor example, certain methods used to repair parts of the building (such as the use of non-breathable paints and mastic asphalt) have caused leaks and condensation. They have accelerated the decay and changed the look of the Tower.  

The conservation project is past the halfway mark 

In November 2019 the top section of the scaffolding was removed and the newly conserved roof with its cross and orb was unveiled. More sections will follow as the rest of the roof and all four clock dials are completed.  

On 21 August 2017 following the 12 noon chimes, Big Ben’s bongs stopped. While vital conservation work takes place, the Great Bell’s world famous striking and chiming is paused to ensure the safety of those working in the Tower. Parliament’s specialist clock mechanics will ensure that Big Ben can still bong for important national events such as New Year’s Eve and Remembrance Sunday.