Mirvac has used prefabrication to cut build time by almost 25 per cent and reduce labour hours by 11 per cent for townhouses in a pilot program that it will now extend across its residential construction portfolio.
At its 911-home Tullamore housing estate in Melbourne’s Doncaster East, the developer compared the construction of two rows of four townhouses – one built using prefabrication and the other by traditional methods – and nearly halved the on-site waste generated by each new dwelling.
Spot the difference: Mirvac’s Stuart Penklis with the prefab townhouses (right) and traditionally built ones (left) at the Tullamore estate in Doncaster East.  Eamon Gallagher
At the test site on the former 47-hectare Eastern Golf Club, which Mirvac agreed to buy for $100 million in 2011, it craned premade sections of double-layer “cassette” floor into place and did the same with wall panels already comprising facade panels, window frames and glass that needed only rendering and painting on site.
“Prefab and off-site manufacture is a way in which we can mitigate [time, material and labour] risks while actually improving safety and helping to achieve our aspiration to send zero waste to landfill by 2030,” Mirvac’s residential head, Stuart Penklis, said.
For a high-cost country such as Australia, developing more efficient construction methods is crucial. Companies including Lendlease, Hickory Group and Aveo have been working on this for years. But the 2018 collapse of prefabrication-specialist builder Strongbuild showed this could be a risky business.
Prefab suppliers to builders can carry large risks in the form of products they carry and banks can be wary about the early release of funds for products that might not be built to specification.
But NSW Building Commissioner David Chandler warned in 2018 that if Australia did not develop a viable local capacity for prefabricated procurement, it would lose 200,000 local construction jobs to overseas suppliers.
As we increase our scale and volumes we’ll start to see the benefits from a cost perspective. But at the moment, it’s been line-ball.
Mirvac’s Stuart Penklis
Mirvac started putting prefabricated bathroom pods in its apartments years ago and it had taken five years to refine the process and products to the level where they have now become a standard feature, Mr Penklis said.
It takes time to get things right. Tullamore’s test involved just four dwellings and the 16-home first stage of Mirvac’s Georges Cove project in Sydney’s Moorebank is expanding the process to 16 homes. At Georges Cove, the company has cut the time from the start of construction to lock-up – the point at which the roof is on and the structure is watertight – from 25 weeks to just 12 weeks.
But it is from the next venture, the 300-home Riverlands project, on the site of the nearby former golf club in Milperra, that the company aims to combine prefabricated walls, floors and bathrooms to maximise the work done in the controlled environment of a factory and reduce on-site construction.
Achieving scale was crucial, particularly as prefab meant a prior outlay of money for materials, Mr Penklis said.
“But actually, that is countered by the fact that your construction programs are shorter,” he said.
“As we increase our scale and volumes, we’ll start to see the benefits from a cost perspective. But at the moment, it’s probably been line-ball.”
He said he could not forecast the benefits of building prefabricated townhouses at scale, but the Tullamore project showed that prefab cut labour hours by 11 per cent compared with the equivalent conventional building process. Labour costs typically account for 50 per cent of the cost of a dwelling.
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