The Palace of Westminster

Dating from 1097 Westminster Hall was a royal palace during medieval times before, in 1547, becoming the permanent seat of both Houses of Parliament. It has perhaps the best example of a hammer beam roof in Europe, is a Grade I listed building and forms part of the UNESCO Westminster World Heritage Site. The hall has suffered from considerable ongoing settlement of the grand Southern steps, designed by Sir Charles Barry in the mid-nineteenth century, and of areas of the floor.

Gifford was appointed by the Parliamentary Works Services Directorate as lead consultant to investigate settlement causes, consider options for repair and recommend remedial measures.

The first stage of the works involved non-destructive surveys which included radar measurements and then careful lifting of stone floor flags, each measuring 1.66m x 1.66m and laid by Robert Smirke in 1834-37, to carry out geotechnical investigation.

Gifford worked closely with the Parliamentary Estates Works Directorate, the Palace Conservation Architect and English Heritage to ensure that all work was in accordance with best conservation practice. The Gifford design team comprised conservation engineers, geotechnical engineers and archaeologists who worked together to develop a solution that permanently arrested the settlement while ensuring that the impact on the historic fabric and buried archaeological remains was both measurable and minimal. The preferred solution included dismantling part of the steps and rebuilding on a stiff piled foundation. Careful refinements to the design ensured preservation in situ of buried remains. Under the floor the ground was strengthened by injecting a stiff cementitious grout under pressure at locations across the floor. The flags and steps were then re-laid.

Gifford developed an archaeological mitigation strategy that included two excavation trenches and six geo-archaeological cores. One excavation revealed that pieces of Purbeck marble trestles from the long-lost King’s Table had been re-used within the foundation of the seventeenth century dais. This royal table was the centrepiece of coronation and state banquets.