Canterbury Cathedral’s Great South Window has won a RICS award

Purcell is happy to share the news that the Great South Window in Canterbury Cathedralhas won the RICS South East region Building Conservation award.

The restoration of the mediaeval stained glass south transept windowrequired extensive work over seven years. The conservation of CanterburyCathedral, a grade I listed world heritage site and scheduled ancient monument,is overseen by Surveyor to the Fabric and Purcell Partner Jo Deeming.

Standing 55ft high and 24ft 9inches wide, the 1420’s Great South Windowholds precious mediaeval glass, including the 12 century‘Ancestors of Christ’.

Four years of research and development revealed issues with failingmediaeval drains, unstable groundwater levels, corroding ironwork and theimpact of previous campaigns of building work. Understanding thesecharacteristics was essential to developing the conservation strategy.

With support scaffold restricting access, the cleaning, setting out,measuring, protection, dismantling, repairs and reinstallation all had to beundertaken by the Cathedral’s masons and glaziers by hand. Many of the stonesweighed more than 250kg, some were half a tonne.

All historic deformities had to be reconstructed exactly, to allow thehistoric glass to be re-fitted unaltered. Bespoke tools for setting out weredeveloped and manufactured, the success of which is evidenced by not asingle glass panel needing to be adjusted upon reinstallation.

Sustainability is at the heart of Canterbury’s conservation ethos of ‘asmuch as necessary but as little as possible’. During construction, the entiresupport scaffold was enclosed to facilitate all-year working and regularworship continued within the Church throughout the project.

The Caen limestone used for repairs was tested to match the characteristicsof surviving mediaeval fabric. Sawn on site and banked and carved by hand, stonechippings and dust were re-used by the mason’s shop in the formation oftraditional lime mortars.

Continuing a centuries old tradition, all conservation works were undertakenon site by the Cathedral’s in-house crafts men and women. The project sustainedsix stone masonry apprentices, honing their conservation and carving skills andnow qualified as stonemasons.

By Jess McCulloch