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WESTMINSTER CATHEDRAL: RE-ROOFING OF NAVE AND CHANCEL

Client: The Trustees of Westminster Roman Catholic Cathedral
Architect: St Ann’s Gate Architects LLP
Quantity Surveyor: Synergy Bare Leaning & Bare
CDM Coordinator: Invicta Safety & Health Ltd.
Contractor: Knight Asphalte Ltd.

Commencement date: 16th March 2015
Completion date: 30th September 2015

Final contract value: approx. £340,000

Located in the City of Westminster, the Cathedral of the Most Precious Blood is the mother church for Catholics in Britain. The Cathedral is a grade I listed building, opened in 1903 and built to the designs of JF Bentley in an early Byzantine style. We have been involved with the Cathedral for nearly twenty years as Cathedral Architects. During that time we have completed a wide range of different projects.

In 2014, the Cathedral were awarded two grants by the WWI Centenary Cathedral Repair Fund, for the re-covering of the nave and chancel roofs. This project addressed the urgent need to replace the existing asphalt to the main roofs of the Cathedral and to renew the abutment details, identified as a priority in our 2013 quinquennial inspection report. The nave roof is divided into three bays, with a further bay over the chancel. At the centre of each bay is a copper-covered concrete dome; numbering four in total.

The works were carried out in a single phase over a 6 month period. The existing asphalt was removed and replaced with a Permaphalt asphalt roofing system. The chancel roof is more steeply pitched, with large steps up to the central dome and curved sections to the north and south. These were an interesting challenge to the skilled asphalt specialists.

The soft brick parapet backs throughout the roofs proved the biggest challenge in forming the perimeter asphalt abutment details, as they were in poor condition in places. To reduce further deterioration of the brick, a three-coat lime render was applied on expanded metal lath. The existing lead parapet flashings remain in a generally serviceable condition, but lead patch repairs were carried out where necessary. Where render could not be applied to the parapet backs of the chancel roof, lead flashings were introduced.

To the new asphalt, a light grey coloured solar reflective paint was applied, which unifies the roofs and performs as well as a standard white reflective paint. Some additional copperwork was required to replace panels in poor condition or disturbed by the asphalting works, particularly to the chancel dome.