STONE CONSERVATION AND LIME MORTAR REPAIRS

Project overview
On behalf of Nick Cox Architects, and the client Wells Cathedral, Cliveden Conservation carried out a pilot phase of works to clean and repair the stonework and sculptures to the central top tiers above the West window. The aim of the project was to design and refine a methodology to be used across the rest of the West Front for future conservation projects.

In the hundreds of years since construction, the West Front has undergone a number of repair phases, most recently in the 1970s and 1980s. Those works are considered the forerunner of lime mortar repairs in the conservation world, and many of these repairs have survived exceptionally well.

Summary of the conservation work carried out
The trial phase was carried out on four tiers of medieval statuary to the West front, and their associated decorative architectural niches. Physical inspection of the building brought changes to the baseline specification that had been informed by a MEWP survey, so a position of trust between the client and the team was essential.

A clear method of recording was established during works to understand the current condition of the limestone, its history of repairs, and to develop new repair strategies. A colour-coded system was devised to mark up photographs, and a pictorial glossary of typical issues needed to be agreed with the client, that all the conservation team could use to record their findings.

Cleaning and removal of pigeon guano, nests and biological growth was carried out prior to assessment, which led to the recommendations for mortar repairs and consolidation of the different elements. Some stone replacement was also recommended, and the opportunity was taken to fix high level finials where these were found to be loose, and vulnerable to falling.

One large and complicated area of stone was identified for replacement, a quatrefoil panel on the highest tier of the building, and this, along with string courses and foliate sections of capitals, were carried out by Cliveden’s team of stone carvers.

In terms of the mortar repairs, many of the materials used in the previous repairs proved no longer available, and a number of samples needed to be created to get the best match in terms of colour and durability. Nick Durnan was invited to assist as a Consultant, having worked on the West Front in the 1980s.

We used Nick’s knowledge of lime, and memories of the materials and methods of application used previously, to create our repair mortars. Different stone dusts and aggregates were mixed to a base mortar of lime to create three colour matches, to use in different locations across the West Front as needed.

One of the most complicated elements of the project was in the application of the mortars themselves. It was critical to the project that the mortars didn’t simply serve to aid water run-off, but preserved the form of the sculpture, without being conjectural, allowing the figures to be read and understood.

 Some of the mortars also served a structural purpose, holding the edges of blistering stone from failing further, and deeper mortars incorporated ceramic dowels. All mortars were kept damp for a minimum of two weeks, before sheltercoats were used to unify the surface and help to aid the reading of the tiers from ground level.

Results
The recording methodology developed by Cliveden Conservation was effective and has created sustainable records which are practical, easy to read and can be digitised. The selected stonework and sculptures have been cleaned and repaired, helping to protect fragile surfaces and restore features and shapes of the figures. It is hoped that the methods developed during the trial phase prove useful for all future phases of works to the Cathedral.