Client: William Anelay
Location: Clifton Cathedral, Bristol
Project: Replacement of roof covering
Construction of Clifton Cathedral started in 1970 and was completed in 1973. It is built entirely from reinforced concrete in two concentric hexagons. The first hexagon forms the main public areas; the second is set above the alter and extends some 40m above street level to form the distinctive cupola.
After 40 years the existing lead work - which covered every roof along with the north facing glazing - needed to be replaced. This presented William Anelay with the task of removing the existing lead
roof covering with access to remain in place throughout the project. New lead was to be installed sequentially from the base of the roof to the cupola. All work had to be carried out while the cathedral remained open to the general public.
Prior to the involvement of Denholm Industrial Services, the access solutions put forward had relied on the installation of large bridging beams. These bridging beams would have been costly, difficult to install and would also have applied massive loads to the structure. The proposal designed by Denholm Industrial Services involved the construction of a light-weight access scaffold, built to the shape of the cupola and supported by adjustable baseplates set against the roof.
The scheme allowed the old roof to be removed simply by releasing a particular adjustable baseplate; removing the covering before tightening the adjustable baseplate to provide support to the scaffold. This sequence was then carried out in reverse for the installation of the new work. The structure was demonstrated to be structurally robust in a very exposed location.