Inside Air NZ’s Biggest Build:  Hangar 4 will be the southern hemisphere’s largest single-span timber roof

Air New Zealand is months from moving into Hangar 4, which, once completed, will become one of the world’s largest single-span timber arch hangars.

Standing ten storeys tall and nearly as wide as a rugby field, the hangar—which will eventually house the airline’s Auckland-based maintenance fleet—will be long enough to fit a Boeing 777, Dreamliner 787 or two single-aisle A320/21 jets and close the doors behind them.

Choosing wood over steel and concrete, due to its strength and flexibility, the build, now about 80% finished, can move up to 300mm in extreme conditions, with construction crews now working around the clock to build the hangar’s 10,000 square metre concrete slab, honey-combed with pipes and tunnels for power, electronics, and drainage.

Designed by NZ-based Studio Pacific, it includes 1,200 cubic metres of laminated veneer lumber (LVL) and cross-laminated timber (CLT), all supplied by Xlam, with the 98-metre structure, set to become the largest single-span timber arch hangar in the southern hemisphere and the first to achieve a 6-Star Green Star rating.

The laminated veneer lumber (LVL) and cross-laminated timber (CLT) hybrid timber arch spans 98 metres. (Image Credit: Renders supplied by Global Pacific Architecture and Air New Zealand)

Speaking to the NZ Herald, NZ Strong pre-construction and innovation manager Jimmy Corric said the timber building is already attracting global interest. Its span is believed to be bigger than another wooden hangar built in Tillamook, Oregon.

And while the Auckland hangar will use steel in the front arches to make a rigid frame for the 80m-wide fabric doors that drop from the roof, the 100% wooden ones in the bulk of the building only use steel in their base plates.

Mr Corric has crafted a scale model of a truss that stands in NZ Strong’s onsite headquarters, and he uses it to explain the process:

“Timber and geometry do what they do best. It can wobble about in the breeze, it is a seismic structure. You either make these really rigid structures that constrain everything or you have structures that move a little bit that allow things to give.”

Wood Central understands that the LVL is made by Nelson pine, shipped to Hunter Laminates in the city, where it is glued into five 25m sections per truss, shipped to Auckland, and then to Xlam in Mangere, where the CLT from Australia is joined to the section before it is taken to the hangar site.

Lying on the concrete slab, the sections are then joined – hundreds of 250mm long screws are used and driven in by grunty battery tools. The finished trusses are erected using New Zealand’s largest crawler crane, usually used to put up wind farms. The 38-tonne trusses are stood up to 85 degrees by the crane and then manually winched upright by workers on two towers standing next to them.

Next comes the roof, made from ETFE (Ethylene Tetrafluoroethylene) cushions filled with air, providing insulation and resistance to wind. The ETFE cladding system is secured using aluminium extrusions and inflated at low pressure to maintain its structural integrity. It is designed to have high corrosion resistance, which is important given the area’s proximity to the sea.

The hangar is part of a new Air New Zealand campus at the Auckland Airport

According to Brendon McWilliam, Air New Zealand’s General Manager of Aircraft Maintenance and Delivery, the new hangar will replace older hangers that date back to the 1960s – as part of a push to future-proof the airline’s maintenance operation for decades to come.

“It’s really a great hanger that allows us to be future-focused for our maintenance staff with doors that shut, protecting in all weathers. It’s sustainable and it’s really built around the future of where we want our maintenance to go.”

“The question we’d ask ourselves is, ‘What does maintenance look like in 50 or 60 years?’ We’re in the cycle now where things are evolving so fast. We had to really think and focus around what’s underground – are we going to be running hydrogen, and do we have electric aircraft?”

Mr McWilliam said using wood fits the airline’s sustainability goals and provides lots of clear space: “We don’t have posts or pillars that we have to work around—it gives us a nice blank canvas.”

Last year, Air New Zealand CEO Greg Foran, who took over the airline at the start of the pandemic, said the new campus will consolidate the entire airline under one roof for the first time in generations.

“We’ve spent the last two years looking at how we can set ourselves up for success as we revive our airline,” he said last year ahead of the campus’s ground break. “We know we work best when we work together, and we have plenty of underutilised space at the airport campus to make that happen.”

Significantly, the airline opted to refurbish its hangar facilities for a cost-effective brownfield redevelopment rather than secure a new greenfield site.

“We have more space than we need in the Auckland CBD and are already paying for a precinct at the airport that has more than enough space to meet even our most ambitious growth projections,” he said. “With building costs increasing and our CBD leases ending, this is the time to get started on the work to bring our people together.

“The way people work has changed – this is our opportunity to set up a world-class hybrid work environment with cutting-edge digital technology so our people have the right tools to build on our history of innovation and deliver great experiences for our customers.”

Auckland Airport opts for a massive timber subfloor over concrete

The new hangar comes after Wood Central, in September, revealed that a major domino in Auckland Airport’s NZ $2.2 billion upgrade—its first for 50 years—has fallen into place, with Hawkins – one of New Zealand’s largest construction companies – signing off an NZ $800 million contract to build the terminal building.

The massive build will see Hawkins install over 600 steel pikes 35 metres into the ground, strong enough to support more than 6,000 tonnes of steel, concrete and timber, which will be used in the terminal subfloor.

“Building in a live operating airport environment is no small task, and while we’re focused on minimising the impact on travellers as much as possible, we know change is disruptive, and we thank travellers for their patience as the build progresses,” according to Ms Hurihanganui, who said the new terminal will “deliver a functional design that is simple and cost-efficient and focused on doing the basics well for customers.”

Designed with a simple and robust exterior structure made of tray-profile steel, Auckland Airport has concentrated its efforts on the interior of the new terminal, delivering a functional design with sustainability elements, such as all-electric heating and cooling and low-carbon materials.

With a single aircraft pier, the interior design employs a river-like circulation path for travellers – inspired by the tidal harbour, volcanic stone fields, and manga surrounding the airport. Timber accents and a cost-effective mix of durable carpeted and rubber flooring create a relaxed feel for travellers:

‘Choosing wood for the sub-floor instead of concrete reflects a preference for low-carbon materials and supporting sustainable aviation.’

Auckland Airport’s Chief Customer Officer, Scott Tasker.

By Jason Ross, publisher, professional in building and construction

Source: Wood Central