The alteration within the castle involved creating significant new openings in masonry walls up to one metre thick and the installation of a new lift shaft.
The new extension included feature glulam trusses, a suspended timber first floor, a concrete ground floor slab and shallow strip/pad foundations. In the collections storage areas on the first floor, precast concrete floor slabs were incorporated, spanning onto a combination of steel beams and concrete block walls.
Externally, the additional impermeable surfaces created by the new parking areas and access road resulted in an increase in surface water run off from the site. This run off is controlled by a belowground cellular attenuation tank, designed to restrict the volume of water to the public sewer and hence reduce the possibility of flooding, all in accordance with the principles of SUDs design. The new car park has a gravel finish with type one sub-base, stiffened with a plastic cellular geogrid.