New Waitomo Caves Visitor Centre, Waitomo June 2010
Sheltered below an innovative woven timber canopy, new amenities for visitors to the Waitomo Caves includes tourist gathering areas, a 250-seat dining, retail, seminar and exhibition areas as well as a café and theatre for Tourism Holdings Ltd.
The cave entrance is accessed from the car park on the upper path while a lower path returns the visitors back alongside the stream exit. Between these paths the amenities were accommodated within a simple base structure that extended the contours of the land. The form of the base is distinguished and separate from the curved geometry of the overhead canopy.
The historic caves were formed from the limestone transported by water over thousands of years, so we wanted to emphasis a connection with the Waitomo stream and the flows of water running through the caves. The canopy gridshell is aligned with the curve of the Waitomo stream. It reinforces the generating idea for this project of a simple lightweight ‘sky shell’ to counterpoint the subterranean cave space that is dissolved and molded out of the ground. The canopy in combination with the caves, create a positive and a negative, if you like.
The structure of the centre is internationally significant. The geometry of the canopy was described by the surface of a toroid and Radiata pine LVL (laminated veneer lumber) was prefabricated into curved (and twisted) ribs in Hunter’s factory in Nelson. These timber I-beams were joined, overlapped in layers, then screwed together as they were assembled on site by Hawkins Construction. The weaving of the timber structure to create a timber net or ‘gridshell’ is recalled by the local hapu as a hinaki or Maori eel trap. The gridshell was calculated by Alistair Cattanach at Dunning Thornton Consultants. His analysis was peer reviewed in London by Happold Structural Engineers, who commented favourably on the strengths achieved with NZ pine LVL and an innovative soft pad connection with the over cladding.
Inflated ETFE (Ethylene Tetrafluoroethylene) air pillows were tethered over the gridshell structure like a tent fly. The long translucent pillows are structurally efficient in spans of 4-5m and followed the lines of the LVL ribs. The gridshell was designed to span across the existing pathways and provide some shelter in the journey to and from the caves as well as maintain a strong connection to the established Kahikatea bush.