Westminster Hall in the Palace of Westminster was founded in 1097, though only sections of masonry remain from this date. Its spectacular hammer beam roof — which dates from 1402 — is thought to be the best example in Europe, and the whole building is Grade 1 listed and part of the Westminster UNESCO World Heritage Site. The Hall's grand southern steps and some areas of floor had suffered from considerable ongoing settlement and our specialists were appointed to investigate the causes, consider repair options and recommend remedial measures.
Working closely with the Parliamentary Works Directorate, the Palace's conservation architect and English Heritage to ensure that all work followed best conservation practice, we took the role of lead consultant. Non-destructive surveys, including the use of radar, preceded careful lifting of the floor's flagstones for geotechnical investigations. Each flag measures 1.66m square. They were laid at the orders of Robert Smirke in 1834-7.
The very wide stone steps were designed by Sir Charles Barry, and date from the mid nineteenth century. The solution developed for the settlement here involved dismantling part of the steps and installing a stiff piled foundation. The ground under the floor was strengthened using injections of a stiff cementitious grout at pressure locations. Detailed refinements to the design ensured preservation of in situ archaeological remains under both areas. The flagstones and steps were then relaid. Our approach is designed to permanently arrest settlement and ensure measurable and minimal impact on the historic fabric and the archaeology.
We also developed an archaeological mitigation strategy that included two excavation trenches and six geo-archaeological cores. One of the excavations revealed that pieces of Purbeck marble trestles from the long-lost King’s Table had been re-used in the foundations of the seventeenth century dais in the Hall. The King's Table was once the centrepiece of coronation and state banquets.