"It needed to reflect Wellington's unique geology, its exposure to the wind, the coastline, and its toughness and ruggedness. The idea of a rock form evolved from these discussions, and we were encouraged to explore this further," says Roberts. "The design was never intended to be an artificial stereotype. This was not about theming ideas. We did not want it to be literal."
The final form comprises three linked structures two large copper-clad volumes and a lower black bitumen-clad rock form that accommodates ramps linking the airbridges with the main building. The fractured form of the structures is enhanced by a black roofing membrane system that breaks up the copper panels, much like geological strata layers. These membranes also have a functional role as gutters and rain-screen waterproofing.
"The geometry of these two volumes is different, which creates a visual tension that you wouldn't get with a typical structural alignment," says Roberts.
The solidity of the rock forms is reflected in their thickness partly determined by the need for a double-skin roof cavity space and to accommodate services.
The two main volumes are linked by a glazed fissure that extends across the roof and down to ground level, bringing natural light into the centre of the building. There are also long windows, like slices cut out of the rock, positioned to frame key views of the runway and aprons.
The rock formation continues on the interior, with the copper wrapping around to semi-enclose each volume. The copper was pre-weathered at the airport to create the patina visible on the interior panels. However, the exterior panels will continue to weather, eventually gaining a green patina.