Technology to "print" a complete house is just around the corner.
Imagine being able to rebuild Christchurch with the click of a mouse. Architects and engineers produce plans down to the last detail using computer-aided design (CAD) software. Then, hit print and - not quite instantly, but after a few days - completed buildings appear before our eyes.
It sounds like fantasy - only one step removed from wishing we could rewind to before the city's devastating quake. Yet it's not that fanciful.
Olaf Diegel, professor of product development at AUT University, reckons that in a decade the technology to "print" a complete house will exist. A decade after that, it should be affordable.
"A lot of this science fiction-type stuff is actually just around the corner," says Diegel, director of the university's Creative Industries Research Institute. "Physically printing the walls can be done today. It's all the other parts that make up a house that they can't quite do yet.
"But they're furiously working on it so ultimately they will have a machine that can be plonked on to a construction site to print the entire house."
"They" are 3D-printing pioneers in the United States and Italy. At the University of Southern California, a team led by Behrokh Khoshnevis has developed a technology called contour crafting.
After the Boxing Day tsunami in Asia and earthquake in Pakistan the following year, which together destroyed hundreds of thousands of homes, contour crafting's "additive manufacturing" method was suggested as a way of rebuilding.
It's envisaged that the mature technology will enable a house of about 200sq m to be built in 24 hours at a fifth of the cost of conventional construction methods.
Enrico Dini, meanwhile, a civil engineer from Pisa, has developed a system called D-shape. A CAD-driven machine that wouldn't be out of place on a car assembly line applies a bonding chemical to sand, in a process akin to creating sedimentary rock - but in a day rather than millennia.
Dini's structures are more sculptural than dwelling-like but British design magazine Blueprint quotes him as saying he would like to build a cathedral - or houses - on the moon. Khoshnevis, too, has his eyes on the heavens. Contour crafting could be used to establish martian or lunar colonies, using lunar regolith - or moondust - as the construction material.
Here on earth, Diegel says, lightweight concrete with a low slump-factor is the usual building material.
"If you're printing with it you want something that doesn't slump." Aeration and chemical additives are used to make sure the material keeps its shape between layers.
The hard parts are the elements that supply our creature comforts - plumbing and wiring.
"There are now modular plumbing systems that robots can clip or braze together. One of the big challenges is not so much the technologies themselves but getting them all to work together in the same space."
It's an issue of choreographing the machines so they don't get in the way of each other.
"You imagine you have one robot printing the walls while at the same time you have others fighting for space to lay the wiring and plumbing.
"They have to be finished their tasks so the printing robot can just keep doing layer after layer without stopping."
As the technology develops, plumbing and wiring will be produced in the same way as the walls, with printers that also work with plastics and metals.
Diegel thinks the term "3D printing" describes the process well, although standards body ASTM International formally refers to it as additive manufacturing.
"The old style of [subtractive] manufacturing is you start with a block and cut away the material you don't need. With this you start with nothing and add material one layer at a time."
Therein lies one of its great virtues - it minimises waste.
The technology will be too late to help with the rebuilding of Christchurch, Diegel says, but could well have a role in the recovery from future calamities.
"It's completely applicable [to disaster recovery] and something we should be talking about."
Combined with another technology - laser scanning - it stands to make replacement of buildings such as Christchurch's cathedral as easy as pressing "print" on a computer.
"With laser scanning, we could go around and scan all the old heritage buildings so we have a digital version of them. Then, when disaster strikes, we could reprint them looking like a heritage building out of the same materials as the heritage building."
Anthony Doesburg is an Auckland technology journalist
