Summoned by bells: McAlpine wins Big Ben restoration contract
Sir Robert McAlpine starts work in the new year on £29m of repairs to the famous clock tower at the Palace of Westminster
Sir Robert McAlpine Special Projects Division has been awarded the scaffolding contract and pre-construction service agreement (PCSA) for a three-year programme of essential works to conserve the Elizabeth Tower, the Great Clock and the Great Bell, also known as Big Ben.
The works have been designed to repair problems identified with the Elizabeth Tower and the Great Clock, which cannot be rectified whilst the clock is in action.
McAlpine will repair and redecorate the interior and renew the building services, conserving significant elements of the Tower, as designed by architects Charles Barry and Augustus Welby Pugin
As the Tower is 96 metres tall, scaffolding is needed to enable workers to reach high levels safely. Sir Robert McAlpine Special Projects Division will begin work on constructing the scaffolding, an essential preliminary step before any following conservation works can begin, in January 2017. The construction is expected to last approximately six months, by which time the scaffolding will have reached the top of the Elizabeth Tower. While the scaffold will be in place for the duration of the works, at least one clock face will be visible at all times.
The approximate fee value for the scaffolding construction and PCSA is £3.5m. The conservation of the Elizabeth Tower as a whole is expected to cost £29m.
In addition to the scaffolding contract, Sir Robert McAlpine Special Projects Division has also been awarded the PCSA for the remainder of the conservation works. The PCSA will be used to allow further detailed planning for the conservation of the Elizabeth Tower, the Great Clock and additional modernisation, while the scaffolding goes up.
While the Elizabeth Tower, completed in 1856 after 13 years of building, remains structurally sound , cracks have developed in the masonry, the cast iron work on the roof and belfry is corroding, and leaks have caused damage internally. There is evidence of serious condensation, leading to problems with damp, cracked plasterwork and rust. Corrosion to the bell frame has caused one of the feet supporting the quarter bells and Big Ben to split. The Ayrton Light, which tops the Tower and shines to indicate that Parliament is sitting, needs to be fully dismantled and restored.
Designed by Edmund Beckett Denison, the Great Clock was first installed in the Clock Tower in April 1859. Parts have become worn and require repair. There are concerns about the pendulum’s accuracy, and the suspension spring, which holds the pendulum in place, needs to be replaced. The clock hands were last removed in 1984. Many of the 312 pieces of pot opal glass used to make up each clock face need to be renewed as a number have cracked over the years. In addition, the cast iron frameworks which hold the glass in place have corroded.
Access to the Tower is via 334 stone steps and evacuation in the event of an accident is carried out using a complex abseiling rig. To ease emergency procedures, a lift will be installed in one of the existing ventilation shafts.
To improve the Tower’s energy efficiency, mechanical and electrical services will be updated and the lights illuminating the clock dials and the belfry will be replaced with low energy LEDs.
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This article was published on 29 Nov 2016 (last updated on 29 Nov 2016).