A completed house made of printed mud in Ravenna, Italy.

Printed homes are all over the place – like mushrooms, appearing almost overnight.

Quick to build, many pilot projects are trialling various technical methods and materials.

Al these pilot projects claim four other principal advantages: they save on material use, they’re cheaper, they require much less labour, and they are more airtight (less draughty) compared to conventional homes.

The real test of their success will be whether residents enjoy living in them. The companies that crack this will be the Ubers of the future building industry, leasing or selling 3D printers to local franchises.

And the most sustainable building material to print with is…mud. But most are using forms of concrete.

Tiny homes

Because of the present sizes of the 3D printers, most of these prototype homes are about the size of a trailer – a comparable size to the 200,000 “prefabs” that were hurriedly built in Britain between 1944 and 1950 to provide cheap, fast housing to solve an acute housing shortage caused by the tens of thousands of homes destroyed by German bombs in World War Two.

Post-war prefabs being erected.
Excalibur Estate in Catford, southeast London, 2017, built by German and Italian prisoners of war.

Made in a factory of precast concrete reinforced with steel rods, and assembled on site, these flimsy, cold bungalows were only intended to last for a decade.

Many actually lasted for decades, sometimes to be eventually replaced by more solid brick structures that occupied the same footprint. They were always seen as homes for the less well off, but many residents loved them so much that they bought them from the council.

It remains to be seen if people will love printed homes as much.

Printing with concrete

AP: Peter Dejong

It’s interesting to compare those original prefabs to the above house, assembled from 24 concrete units “printed” in 120 hours by a machine that squirts layer upon layer of concrete at a factory in Eindoven, Netherlands, and then trucked to the site to have finishing touches and roof added.

There are plans to build a total of five houses, and future homes will have more than one floor.

Like most 3D printed house developers, Theo Salet, a professor at Eindhoven’s Technical University, claims they use 30 per cent less material than traditional construction methods.

But they still use concrete, which has a considerable ecological footprint, and, as the unit in the photograph above shows, they will suffer from thermal bridging.

Printing with mud

These problems are solved by printing with mud. Building with mud is a traditional technique called rammed earth. The WISE educational academy at the Centre for Alternative Technology, Wales is one modern use of this method.

An Italian firm WASP, has now printed a house of mud in Massa Lombarda, Ravenna – Italy, using one of the largest 3D printers in the market, BigDelta.

3D printing with mud: the WASP house.

The 323 square foot house, named Gaia, is made using local soil, straw (left over from harvesting rice) and lime. The straw acts as a binder. It is based on “cob” building, a traditional system of building around the world.

From a sustainability angle this is greatly preferable to concrete, as it stores atmospheric carbon in the building shell. The material has a low transport footprint too as the soil is local.

The critical criteria are the drying time (to avoid cracking) and the consistency of the material – which is an issue for concrete also.

With inferior consistency comes a poor structural performance: structures may collapse. Quality control is therefore crucial.

To account for this the WASP team perfected the mix to 25 per cent soil taken from the site (made of 30 per cent clay, 40 per cent silt and 30 per cent sand), 40 per cent straw chopped rice, 25 per cent rice husk and 10 per cent hydraulic lime.

It took 10 days to print the 30 square meters of wall (thickness 40 cm) for a total materials cost of just € 900.

WASP claims justifiably that it has now developed a new circular model of housing entirely created with reusable and recyclable materials, sourced from local soil, carbon-neutral and adaptable to any climate and context. It is calling its model TECLA (from Technology and Clay).

Small is beautiful

Smaller homes are better than larger ones, from a sustainability angle, at least.

They have a lower ecological footprint as well as area footprint, since they use fewer materials and require less energy to heat or cool than a larger home.

3D printing of homes is also giving rise to buildings with curved forms and beautiful geometries, like this floating home in the Czech Republic.

Another advantage of 3D printing is that the need for formwork is eliminated. Formwork is extremely wasteful of timber and a big cause of deforestation.

One of Mighty Buildings’ 3D-printed house modules being delivered in Livermore, California. Credit: Mighty Buildings.

Labour loss

3D printing will also decimate the construction industry if it takes off, something the unions have yet to wake up to.

In the USA, California’s Mighty Buildings reckons it saves 95 per cent on labour hours, while doubling the rate of traditional construction, and produces ten times less waste.

Their system therefore puts construction workers out of a job, with automation replacing four out of five labour hours.

Mighty Buildings uses extrusion printing of an ultra-strong stone composite material that’s claimed to be termite-proof, fire-resistant, and water-resistant. While mud homes can be made water and fire-resistant, termites can be a problem.

Mighty’s Light Stone Material (LSM) is a thermal composite that hardens when exposed to UV light and is similar to Corian, a typical kitchen countertop material.

Mighty Buildings claims its process saves 20-30 per cent in costs compared to a traditional prefab process, as the machine prints the entire structural shell of the home, instead of sections for on-site assembly.

Artist’s impression of a 3-D printed housing estate planned by California’s Mighty Buildings.

Developers the Palari Group is using a panelised Mighty Kit system, which features 3D printed polymer composite panels prefabricated and shipped from Oakland, to build what it says will be the first 3D-printed zero net energy neighborhood in the United States. The homes will feature photovoltaic panels from Tesla Solar and Powerwall.

These will be 1,450-square-foot, single-story homes. Despite the visual similarity to the post-WW2 homes above, these compare to their minimum floor space of 635 square feet (59.0 m2), and maximum 7.5 feet (2.3 m) wide (to allow for transportation by road)

Mighty Buildings’ 3-D printer.

In the future Mighty Buildings hopes to develop a fibre-reinforced material comparable to steel, that would allow the 3D printing of multi-storey, multifamily homes for dense, urban housing.

3D homes around the world

India’s first 3D-printed home was completed in April. It is a single-storey home of about 56 square metres located in the southern Indian city of Chennai and took five days to build.

ICON is another firm using 3D printing to create affordable homes for low-income or homeless populations. Partnering with a non-profit called New Story, it is to build a 3D printed neighbourhood in Mexico for rural populations.

ICON was the first company to obtain a building permit in the US for a 3D printed house, in Austin, Texas. Its Vulcan II system can print an 74 sq m house in 24 hours for less than $4000.

In China, multi-storey apartment buildings have been assembled from printed modules by Winsun, which claims it can build 10 houses in 24 hours.

Apis Cor, a Russian company, has built a 37 square foot house in 24 hours that costs just over $10,000 to make. It has also built the “world’s largest” 3D printed building in Dubai, UAE.

UAE is heavily supporting 3D printing construction. Last year it completed the world’s first 3D-printed commercial building, a 243 square metres office for the Dubai Future Academy. One 3D printer took 17 days to print the basic 6.1 metres  high, 36.1 m long, and 12 m wide building.

Dubai wants to 3D print 25 per cent of its new buildings by 2025. Given its highly dubious history of treatment of migrant construction workers from south Asia, that’s probably not a bad thing.

The chances are, by 2035 millions of homes will be being constructed this way, if the pace of urbanisation accelerates as predicted.

Of all the above, the only one I’d consider living in is the mud home. The material is natural and breathable and zero, if not negative carbon. It is probably one of the cheapest, most sustainable homes on the planet, partly because at the end of its life it will be easy to dispose of with no negative consequences, unlike concrete homes.

And I’ve also always fancied a round house. The only thing is, I’ll have to buy round furniture to fit inside it.

David Thorpe is the author of Passive Solar Architecture Pocket Reference,  Energy Management in Buildings and  Sustainable Home Refurbishment. He lives in the UK.

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  1. I’m not sure the labour loss is the tragedy it’s being portrayed as. The construction industry is struggling to find enough skilled tradespeople.