AN INVESTIGATION has begun into why one of Chester’s best-known
and important historical buildings is sinking.
Structural engineers and archaeologists have dug trial pits to investigate the cause of subsidence affecting the massive sandstone Propylaeum at Chester Castle.
Designed by Chester–based architect Thomas Harrison, the Grade I listed entrance to the castle is considered one of the best examples of Greek Revival Architecture in the country.
In ancient Greece, propylaeums were constructed as ceremonial entrances to sites of great importance.
At the time Harrison, best known in Chester for his design of the Grosvenor Bridge, was the most important architect in Northern England.
Recent subsidence has caused problems to the roof of this much photographed structure, allowing water to seep inside.
Some believe work on the castle is long overdue, and in 2009, historian Dr Gavin Stamp wrote in satirical magazine Private Eye that Chester Castle was a “supreme example of municipal neglect and philistinism”.
Council officials have said the work to determine the reasons behind the subsidence should take about two weeks to complete but they were unable to come up with an estimated figure of how much the work would cost due to the uncertainty surrounding the subsidence and the ongoing consultations with English Heritage to ensure the building is restored properly.
Charlie Seward, director of growth and prosperity, said: “We believe the cause of the subsidence is linked to the structure’s 18th century foundations and possibly the modern installation of electric cable ducting supplying power to the castle.
“At present, in conjunction with English Heritage, we are considering the most suitable form of underpinning to prevent further subsidence and deterioration.”
Scheduled Monument Permission is needed for the excavations on both sides of the Propylaeum, which was finished in 1815 to complete the rebuilding of the outer-ward of the medieval castle.
Mr Seward added: “Council archaeologists will be monitoring this extremely important project which is part of the council’s commitment to preserve the historic buildings within its care.
“Quite obviously, on a Scheduled Monument site, there is the possibility the excavations could provide interesting information for our archaeologists. Although it is very early days yet, I understand they have revealed part of the original parade ground and some medieval content.
“Whilst the subsidence must be arrested, it is important to stress the building is not in imminent danger.”
As part of the Listed Building Consent application, CWaC commissioned two local companies, Ramboll UK and Russell Geomatics, to prepare a schedule of works.
A laser scan of the structure has already been carried out and these digital images will be used to monitor any further deterioration or movement.
Other much needed refurbishment of the Propylaeum will include: waterproofing of the roof structure; repairs to stonework and mortar joints; cleaning of the stonework; improvements to the current rainwater drainage system; existing lighting replaced with more elegant and energy efficient fittings and removal of redundant cabling.
CCTV will be installed to deter misuse of the area; gates and railings cleaned and repaired and repainted.
Minor repairs will also be carried out to the stone-wall boundary of the castle’s parade ground and new tarmac laid around the Propylaeum structure.