History and restoration
History | Restoration
How was the building restored
The Structure Restoration by Shepley Engineers
In January 2000 the temporary offices, workshops and support services were established and the Shepley restoration team took up residence at the site. The initial stage of the project involved the design and installation of a complex birdcage scaffold system, designed to enable, not just the dismantling operations, but also to facilitate access for the lift shaft construction, and re-erection and glazing activities.
From the scaffold, access was permitted to the upper roof levels for the first time in over forty years. A detailed survey was undertaken to establish and record the exact location of the principal parts. The results revealed that the principal building datum’s were remarkably within a 10mm tolerance from an established central base line. A testament to the skills and building techniques of the original designers and engineers, Mackenzie & Moncur.
Each and every part of the structure was labelled with a unique reference number to record the restoration history of the part. A catalogue recorded the condition of the part as well as the processes and treatments applied to it during its restoration.
Careful dismantling commenced on the 15th January and by June all that remained standing were the eight main columns, the lower roof lattice support aches and the gallery beams. These items underwent a wet abrasive blast cleaning process and were then painted in-situ.
All of the dismantled parts were transported to the Shepley facility at Shafton, South Yorkshire where the experienced restoration team worked to retain as much of the original structure as practicably possible.
The condition of many parts was far worse than had been initially anticipated, weathering and water ingress had taken their toll. This necessitated many more replacement parts, such as glazing bars, purlin mouldings, the principal perimeter structural beam and the support columns at the gallery level.
The manufacture of new parts was entirely faithful, with the form and profile of the original part precisely replicated. New cast iron parts were produced in spheroidal graphite iron as opposed to the original ‘grey iron’ castings. These modern foundry materials result in castings with enhanced structural attributes without compromise to aesthetic properties. Many different and specialist repair techniques were adopted during the repair of damaged components, putting the experience of the skilled craftsmen to good use.
After repair or replacement each part underwent a blast cleaning process, followed by the application of a five-coat epoxy paint system in strictly controlled conditions by qualified inspection technicians.
The first restored parts arrived back on site on the 22 August 2000 and the re-erection process began. Without compromise, parts have been replaced to their exact original location. Our target installation and assembly tolerance of 3mm was achieved. Quite an accomplishment during one of the wettest periods recorded in the local area.
Installation of the 3712 panes of individually templated 4mm, heat soaked and toughened glass commenced on 15th January 2001 and on the 1st of February the structure was ‘topped out’ with the fitting of the weather vane.
The porch assemblies and spiral staircase were the last part of the structure to be erected. The September 2001 completion with all of the difficulties we have encountered en route, including works to the new basement facility, lift shaft, tunnel and boiler house is evidence to the application and dedication of the individuals involved. Special recognition should be given to Charlie and his core team whose methodical and uncompromising restoration approach made the delivery of the project possible.
We have taken great pleasure as well as a little pain from our involvement in this majestic restoration.
Paul Scott
Engineering Director
Shepley Engineers Limited
