The museum already has four large buildings "popping at the seams" with its vast collection, and curator Jason Rhodes is "desperate" to get another building up to cater for the facility's continual growth.
Excavation work on an immense hole at the rear of the museum's Wanaka Airport site has been under way for more than three years. Measuring about 68m wide, 80m long and 9m deep, the hole will eventually contain three storeys of display space below ground and two storeys above ground.
Consents have been issued for the first two stages of building work, which will add 3640sq m of floor space to the facility, enabling Mr Rhodes and his sister Debbie - who jointly manage the museum - to "un-squeeze" the roughly 700 vehicles, dozen aircraft and 60,000-plus toys and small items crammed into the facility.
With more than 50,000 other toys in storage and a constant supply of vehicles and smaller items from the siblings' father, Gerald - an avid Christchurch collector who established the museum in 1995 - the new hangar will "future-proof" the popular family attraction.
Construction was meant to begin last year, but the Christchurch earthquakes had been "a big hindering point".
"Since Christchurch, it's changed the way buildings are processed and drawn up, especially with this, because it's a little bit different to your average building," Mr Rhodes said.
"With our floors, the loading is greater than car park buildings because our vehicles are heavier. We need to make sure our load weight is calculated correctly."
While normal car parking buildings were built to hold about 25lbs per square foot, the museum hangar would require a load capacity of 50 to 75lbs per square foot, he said.
"So if we want to hang a plane from the rafters, we can."
Mr Rhodes said he expected to approval "any day" from the team of engineers working on the project and was hopeful the building's foundations would be in place by Christmas so the above-ground work could proceed quickly in the New Year.
"The time-consuming part [the earthworks] is done."
The new building will also cater for functions, trade shows and international film production work.
