The visitor centre is an 8 x 35m two-storey building; the ground floor - housing exhibition space, shop and WCs - is enclosed with block walls clad with horizontal 130 x 20mm iroko boards screwed with triangular spacers to an iroko frame. The first floor, a restaurant and kitchen, has walls of frameless glass, set back 1.9m on the south and east elevations to create a terrace. The iroko cladding rises 1,100mm above first floor level, supported by a steel SHS framework, to create a continuous solid balustrade to the terrace.
The restaurant and terrace are covered by a stressed-skin plywood roof supported by a single row of Y-shaped steel columns resting on the first floor, a composite concrete deck on 254 x 254mm UC beams. The roof, 780mm deep and tapering at its edges to a delicate aluminium nosing, is formed of an 'eggcrate' of 6mm-ply ribs at 400mm centres glued and screwed to upper and lower layers of ply to form a monocoque structure. It is covered with rigid insulation and a singleply membrane. The soffits on both north and south sides are lined with silver polyester powder-coated aluminium panels.
The double-glazed glass panels on the north side provide stiffness to the roof structure. The 16mm toughened outer panes are glued to back-to-back angles, fixed in turn to the roof and bolted to the block wall at the base.
On the south side the glass panels are not fixed but restrained between the backto-back angles, allowing the roof to move, for instance under snow load.
The terrace is floored with an iroko deck and an inverted roof which drains to a perimeter gutter neatly concealed within the wall.