In plan the glasshouse is an ellipse; it is covered with a 5,000m 2domed glass roof supported by a series of twenty-four arches comprising 150 x 248mm T-sections welded to the tops of 323. 9mm diameter CHS tubes. The longest arch spans 54m and rises to 14m above the main floor.
The arches spring at 4m centres from a concrete ring beam and shell structure at the perimeter of the glasshouse. At the south side the ring beam tilts gently towards the ground; at the north side it is raised on columns. The structure is lined with earth banks grassed with meadow turf.
The ring beam flanks a wide perimeter gutter lined with granite setts and running below the glass. Rainwater, draining through hoppers into two 70 000 litre underground tanks, is re-used.
The CHS arches taper at their ends to solid cones, each threaded to receive a solid stainless steel bar and 175mm diameter sphere. This sits in a hemispherical socket fixed down to the ring beam.
The joint allows rotation to accommodate any movement due to thermal expansion of the arches.
Trapezoidal 4 x 1. 5m singleglazed laminated glass panels are silicone bonded at their edges to a natural silver anodised aluminium subframe which is clamped to a main framing system. This is supported on adjustable stools welded to the structural T-sections.
Rainwater drains into the sub-frames and then into the main frames, which are each lined with an EPDM gasket and contain the track for a safety harness system.
Groups of opening lights are opened by synchronised screw drives. Cabling concealed in the frames links them to a computer.