The museum is housed in a six-storey 1960s building which has now been extended and refurbished to include a new gallery along the west side, and a four-storey foyer, glazed on the front facade with a Planar frameless glazing system.
The new facade is formed of a series of 1.8m-high double-glazed glass panels. It forms a sinuous curve on plan, created by faceting the panels at their joints. At the east end the glazing returns to meet the projecting stone-faced concrete plinth of the original building. The roof of the foyer is also formed of frameless glazing.
Support and wind loading to the glass are provided by a row of 450 x 150mm tapered rhs mullions which rise 14.4m to the roof, where each is pin-jointed to a projecting 200 x 100mm rhs. A series of cast steel connectors, pin-jointed at the ends, connect the mullions to four-armed cast steel 'spider' brackets, which are fixed with Planar bolts to the corners of the glass panels. The edges of the glass panels are jointed with silicone.
The corners of the Planar glass facade have no structural support. To enable loads to be transferred to ground level at the corners, hardwood setting blocks were inserted in the silicone joints. The glass corner is edged with a 1.6mm stainless steel corner trim. The roof panels at the corner are connected by a stainless steel spring-plate.
On the original building facade the glazing was surrounded by a projecting precast frame. The edge of the new glass facade had to be notched around the frame. The glass panels, set in a stainless steel channel, are notched around the concrete frame and trimmed with a black Alucobond rainscreen cladding system.