As floods, hurricanes, earthquakes and volcanoes destroy or damage urban areas with growing frequency large numbers of people will need to be rehoused. The proportion of people living in towns and cities is expected to keep growing – it is already over 50% - and many of these extreme natural events occur in or near them because they tend to be built close to
- Tectonic fault lines – because mineral wealth is concentrated in such places
How do you rehouse the population of a large shanty town flooded as the sea level rises? How do you rebuild a large part of a modern city demolished by an earthquake?
It is too late to undo the damage done by man already, in the sense of accentuated climate change and of shoddy architecture in the wrong places. Millions of people are likely to need rehousing in the coming decades as extreme climate events increase even faster than predicted and as people continue to flock into cities. Providentially, a new kind of building technology is evolving fast and could be ready for serious, in-field use within a decade: 3 dimensional printing of houses.
3D house printing is achieved in a manner similar in principle to the 3D printing already being used. For example, aircraft wings can be designed on a computer and printed layer by layer by extruding the appropriate material through a computer controlled nozzle. There is even a widely available 3D printer costing about a $1000 available to consumers, called the Cube.
It enables you to print out real, physical objects instead of symbols on paper. The set-up for constructing a house would require an overhead gantry from which the printing nozzle would be suspended. The movement of this nozzle, and the rate of supply of composite fibre concrete to it, would be controlled by software defining the structure of the house. This special concrete, which retains its shape while still wet, would be deposited layer by layer, gradually building up the walls. At intervals the printing would be paused to allow floors, insulation, wiring, plumbing and drainage pipes to be installed. The whole process should take less than a day. An engineering professor, Behrokh Khoshnevis, at the University of Southern California, is behind this idea. See this news item.
Apart from helping communities to recover from disaster the 3D printing principle could be used for house building in normal situations. There are large numbers of people living with minimal protection against the elements and deprived of comforts most people reading this have come to expect. There must be some way of combining this method of building with the installation of sewage systems and power grids.
Khoshnevis also proposes using 3D printing as a way of building space colonies in advance of the intended inhabitants. I have not looked into this but it could be more cost effective than transporting prefabricated modules if you wanted to build a colony. It would be a matter of transporting one gantry plus the material rather than numerous modules which would have to be skilfully handled and put together. I suspect that the total freight storage space needed to transport the modules would be larger than for the 3D printing system.
One potential of present small scale 3D printing is its use as a basis for custom manufacturing units in shops to help regenerate High Streets. It could possibly be combined with skilled craftsmanship to finish off a basic form.
This is powerful technology and it is difficult to imagine it not being used in a big way somehow.
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