NZ's first onsite 3D-printed home

Kirill Ilin's construction company Amcrete constructed the concrete walls of their ground-breaking new four-bedroom prototype "layer by layer by layer" right on its Waiuku site.

He says houses made with concrete poured by a computer-controlled 3D printer are energy-efficient, quick to construct, and, because of their durability and recyclability, also sustainable.

"At the end of life, a timber house goes in the landfill. You can't separate things. It's all sandwiched together. When you break the house, it's just a pile of rubbish... With concrete, it lasts three times longer, and when you're done, you can break it up, recycle it and reuse it," Ilin tells RNZ's Afternoons.

Currently, Amcrete constructs 10 to 15 3D-printed concrete houses a year from panels printed in a factory, which are then brought onsite to be erected with a crane, although Ilin says this is "a whole rigmarole really, quite labour-intensive".

In contrast, 3D printing onsite involves a construction process similar to the laying of concrete blocks via a computer-controlled concrete pour by a "very big" machine set up over the whole house area.

Amcrete's new architect-designed show home was built this way, Ilin says, with the walls printed as "shells" which were then reinforced and filled with concrete in a process that takes 20 to 30 days.

The concrete walls were then spray-plastered with a mixture of sand and cement before the installation of windows and doors.

"[Our machine] prints the whole house, and it goes layer by layer by layer, the whole house lifting up at the same time.

"Instead of 10 guys working there forever… we only need a couple of guys onsite to look after the whole thing."

For the new homeowner, a concrete house made with onsite 3D printing costs about the same to construct as a weatherboard house, Ilin says, and can be completed a bit faster.

Houses built with 3D printing onsite cost about three to four times less to build than comparable houses made of concrete, he adds.

Concrete homes also last around three times as long as conventional weatherboard houses, Ilin says, and can be constructed up to 40 percent faster than a "normal" house.

"Timber frames are the cheapest way to build and comply with building code, which itself only sets a minimum legal level for building to exist, right? I think we deserve much better houses for the value you have to pay. Concrete houses easily exceed minimum performance standards for durability, longevity."

While people generally perceive timber as a "green" material, Ilin says, concrete lasts three to four times longer, is fully recyclable and because concrete walls have a large thermal mass, has an energy-saving advantage.

"The house can maintain the temperature throughout the day, the year, and it doesn't matter what the season is.

"You don't even need to run heat pumps. [Concrete] will maintain the temperature throughout night and day at a constant, comfortable 20, 22 degrees."

While Ilin says his company is "pretty comfortable" constructing up to 15 houses a year with their existing 3D printer, if demand increases, they will set up a "bigger, better" operation.

Right now, though, he's feeling proud to be part of what he believes is the biggest development in the New Zealand construction industry for a long time.

"We haven't had any massive breakthroughs in the technology of how we construct buildings for quite a while now, and this is probably the biggest leap that we've had in like a decade.

"We got it all done, and [the house] looks great."