Independent steel structure within a stone shell pavilion
The visitor centre - a ground floor exhibition space and first floor gallery - is designed as a delicate steel structure standing independently within the stone shell of a 17th century pavilion. On its north side, the first floor gallery flanks the original stone wall; on the south side it is unenclosed, acting as a continuous balcony from which visitors can look down on the floor below and beyond to the glazed screens of the south elevation. The floor edge is protected by a wide oak handrail and a glazed balustrade.
The new first floor and roof act as diaphragms to provide lateral support to the original walls, especially the north wall which leans in as it rises.
The roof consists of 457 x 152mm universal beams covered with an insulated steel deck. The first floor is of cast in situ composite construction on 203 x 203mm universal beams which are edged with steel channels.
On the north side, the first floor and roof are supported by a row of box-section 150 x 60mm fabricated steel columns/beams, welded to form an L-shape. Delicate 30mm-diameter steel rods with escutcheons at their ends connect the original north wall at first floor and roof level to the box-section columns, transferring loads to the horizontal diaphragms.
On the south side, floor and roof are supported by a row of paired back-to-back 200 x 55mm steel channel columns.
At first floor level, each universal beam is welded to a projecting steel plate slotted into the gap between the channels. At roof level, each universal beam rests on a 30mm-diameter rod slotted between the channels.
The wide oak handrail is stiffened with steel sections and plates to span 3.5m between the channel columns.