The earth beneath our feet is arguably the world’s most sustainable building material – and it has stood the test of time in landmark buildings such as Spain’s Alhambra. UWA is exploring the benefits of rammed earth construction and participating in an ARC Linkage project with industry and government.
It costs nothing, is readily available and durable, and those living in homes made from rammed earth laud its thermal qualities and distinctive beauty – yet it is still regarded as an ‘alternative’ material. Some see it as ‘a poor man’s material’; others speculate it must be pricey because it is featured in glossy design magazines. There are more than a few myths surrounding rammed earth!
To sort fact from fiction, UWA recently hosted a conference that brought together engineers, specialist contractors, architects and soil scientists with a shared passion for the beauty and benefits of rammed earth. It was co-chaired by Associate Professor Daniela Ciancio and Assistant Professor Chris Beckett of the School of Civil, Environmental and Mining Engineering.
A compacted, formed and dried mix of soil and water, rammed earth has wide appeal – for remote housing, and for architects drawn to its distinctive earthy qualities. As a construction material it endures – think of Spain’s Alhambra, an 11th century palace and fortress complex that Moorish poets saw as “a pearl set in emeralds”, and China’s Great Wall, built 2,500 years ago to repel the Middle Kingdom’s northern invaders.
With this State regarded as the cradle of rammed earth in Australia, and with UWA engineers researching its thermal qualities, the University was the obvious location for the First International Conference on Rammed Earth Construction.
Keynote speakers from the UK and China were joined by UWA engineering graduate Stephen Dobson who established Australia’s first rammed earth company Ramtec, in 1979. Mr Dobson, who has built more than 750 rammed earth structures in Australia, is an industry partner in an ARC Linkage research project with UWA, Durham University in the UK, Scott Smalley partnership and the WA Department of Housing.
“Australia now leads the modern world in quality and volume of modern rammed earth, so you’ll find it from the deserts to the snowfields,” says Mr Dobson. “Applying modern engineering to structural design, thermal modelling and construction methodology – and marrying this with architecture’s ability to capture the essence of the material – has ensured that an ancient building method is being revived.
And it’s the cheapest way to deliver high thermal mass walls that absorb coolness at night in summer and carry this coolness through the heat of the following day.”
Mr Dobson counts among rammed earth’s environmental credentials its good acoustic properties, high thermal mass and hygroscopic properties.
“The future of rammed earth will significantly be determined by people at this conference who will now have greater confidence in using it,” he told delegates. “For more than 30 years, many individuals have rammed away, often alone, but now we have an emerging synergy. We are all moving onwards and upwards.”
So enthusiastic were participants from 11 countries that several offered to host the next conference. Conference co-chair Dr Daniela Ciancio says its success had much to do with the fact that delegates were able to exchange knowledge and experience.
Dr Ciancio explains there are two basic types of the material: unstabilised rammed earth, a clay-rich soil and water mix with no additional additives that is embraced by ‘green’ architects and builders; and a cement-stabilised mix that accounts for 98 per cent of rammed earth buildings in Australia.
“Proponents believe that stabilised rammed earth increases the building’s strength but it also increases its carbon footprint,” she says. “Further strengthening can also be achieved with steel bars, a method widely adopted in earthquake-prone California and in Canada with its climatic extremes requiring double skinned insulated rammed earth walls.”
Dr Ciancio says by the end of the conference, a list of issues had already been compiled for the next meeting, including addressing the lack of a national building code for engineers and builders – something her research group at UWA is working on.
“We’re working on a draft code supported by practitioners and academics to submit to Standards Australia. We’re also addressing the need for software that takes into account the material’s unique properties when calculating green star ratings,” says Dr Ciancio.
Mr Dobson, who heads the Earth Building Association of Australia, says with no big lobby group for this niche industry such issues remain hurdles. “The Federal Government needs to update the building code and change a thermal rating system set up to suit sealed light-weight insulated boxes not high thermal mass materials. This has already been partly done in Europe,” he says.
Dr Ciancio, who established a rammed earth research group at UWA in 2008, spoke about the University’s current ARC Linkage project that aims to improve housing in remote
Aboriginal communities. Her group’s Kalgoorlie ‘laboratory’ comprises two rammed earth houses – with embedded sensors collecting information – built with funding from the Australian Research Council and the WA Department of Housing.
With sustainability becoming central to decision-making about housing, this engineer is confident that UWA’s research will help to advance the adoption of a construction material with much to offer.