The building (90 x 25m on plan) has an undulating gridshell roof, formed of 80 x 50mm larch laths separated by 50mm- and 75mm-deep larch shear blocks. The gridshell is braced with a double layer of plywood which supports an insulated standing-seam aluminium roof covering and a rainscreen of 100 x 20mm oak boards at 135mm centres, which are fixed to 75 x 35mm oak bearers; the standard seam clips of the aluminium roof were adapted to support the bearers.
The glazed main entrance is set between two sloping 'banks', concrete-slab structures enclosing the greenhouse and other 'back of house' functions.
They are planted with juniper and rise to a glazed clerestory.
The gridshell roof extends over it, incorporating at its edge a CHS tube-ring, containing the internal forces of the structure.
To accommodate the very considerable deflections of the roof (plus/minus 100mm), due to snow load and wind forces, the clerestory glazing frame is cantilevered from the concrete slab, incorporating an EPDM movement joint at the head.
Inside, the joint is screened by a ply fascia, and outside by a strip of 10mm toughened glass in the same plane as the glazing.
Rainwater drains along the standing seams of the roof into an inset gutter, then discharges on to a gutter at the clerestory's base and drains underground by means of a syphonic system.