Hangar 4 is a large-scale, operationally critical maintenance hangar with a total floor area of 16,500m².
The design achieves a 98m clear span and a 35m-high internal volume, creating the aircraft-scale enclosure required for widebody maintenance while integrating with an active, tightly constrained airside precinct.
The engineering solution centres on a long-span arched truss system that uses timber in a hybrid, performance-led way: LVL top and bottom chords paired with CLT webs, supported by CLT timber purlins and LVL runners beneath an ETFE envelope. This configuration addresses span, stiffness, and weight while responding to the coastal environment, where corrosion resistance is a real consideration. Timber was chosen after a timber-versus-steel comparison, and it was selected for environmental benefits, light weight, seismic flexibility, and durability, with supplier input confirming the option was cost competitive.
Construction innovation was integral to making the timber engineering achievable at this scale. XLAM supplied the CLT and LVL package (including LVL sourced from Nelson Pine) and validated the geometry with prototyping. Each of the nine trusses were designed as five preassembled sections, enabling safe transport and controlled lifting. Hinge steel base connectors allowed controlled twist and movement during lifting, reducing risk in high winds and improving installation safety.
The structure’s form is the architecture. The slender timber elements and ETFE roof create a vast space with a luminous, floating quality while maintaining the clear working volume required for aircraft. Mass-timber provides a calmer aesthetic with fewer large pieces compared with the steel. The timber trusses were assembled flat on the ground, fixed at their ends with large steel hinges, then rotated into place using New Zealand’s largest crawler crane, an approach shaped by the site constraints and ongoing adjacent operations.
Hangar 4 demonstrates timber’s viability for large-scale infrastructure through precision manufacture, complex logistics, and connection design. XLAM reports 7,141 individual timber components, with each truss using 12,500 screws (250,000 across the project), underscoring the level of engineered detailing and quality control. Transport planning included 3D-scanned routes and specialist trailers to move components across multiple sites over an ~860km journey.
The project also links timber engineering to measurable operational outcomes: ETFE delivers daylight and insulation, eliminating the need for active heating, and simple ventilation strategies (façade louvres and large overhead fans) support year-round comfort for maintenance staff. XLAM also reports the CLT package sequesters 469 tonnes of CO₂, reinforcing the structural system’s embodied-carbon advantage alongside its engineering performance.
