As a construction technique, rammed earth has well and truly has stood the test of time.
It has been used to magnificent effect to create some of the world’s greatest and most ancient structures, including the Great Wall of China. Why is it then that despite being a tried and tested building technique for centuries, its use is rarely considered for the construction of modern buildings such as offices and houses?
One of the major reasons appears to be a lack of knowledge and a lack of real understanding.
Rammed earth walls are constructed by ‘ramming’ a mixture of gravel, sand, silt - and a small amount of clay - into place between flat panels called formwork. Traditionally, the end of a wooden pole was rammed into the earth mixture to compress it, but modern technology replaces the pole with a mechanical ram. Most modern rammed earth walls are built using cement as a stabiliser and are typically 300 millimetres thick for external walls and 200 millimetres or 300 millimetres thick for internal walls.
Although rammed earth itself is ancient, research into its contemporary use is quite new when compared with other more traditional construction materials such as concrete, steel and timber. Unfortunately, this lack of research has led to a lack of understanding of the material, its structural properties and its practical uses.
While the rammed earth technique has been employed in Western Australia in the past, it is not a common construction material outside of the state – although its use became popular for a period in the 1980s particularly around the Margaret River region. Its rarity and specialist nature also tends to be result in a relatively high cost, as it typically requires high levels of control over material sourcing and expensive formwork. While basic materials for rammed earth making are readily available across Australia, supplementary cement and formwork may have to be transported long distances, increasing environmental and economic costs.
Another obstacle is regulation, or the lack thereof. In Australia, as in most countries, there is no official building code for rammed earth so the prospect of working with an unregulated construction technique has discouraged many building designers and architects from even considering it, let alone making it the cornerstone of their projects.
A further barrier to utilising the technique in this country is the thermal assessment of newly constructed rammed earth buildings, as imposed by the Building Code of Australia. With all building plans subject to thorough testing via computer simulation, all proposals must now achieve a rating of six out of 10 stars to receive building approval.
Finally, many proposals have failed to perform well under computer simulation in the past, leading to frustration and a lack of confidence in the use of the technique among the construction fraternity, despite feedback to the contrary from occupants of rammed earth dwellings.
However, interest in the design and development of more environmentally-friendly and affordable houses is now greater than ever. Researchers, building designers and architects are slowly beginning to investigate the different properties of rammed earth with the aim of promoting the wider use of the construction technique.
As this interest increases, support is slowly building momentum. Good networks are now becoming established across Australia, including national not-for-profit organisation the Earth Building Association of Australia (EBAA), which was "formed to promote the use of Unfired Earth as a building medium throughout Australia." As a result, specialist information relating to the use of rammed earth as a technique, and the achievement six star compliance, has never been more accessible.
So what makes rammed earth constructed buildings different and are they worth the effort?
To start with, rammed earth buildings are full of originality, character and suit a wide range of architectural styles. The natural appearance of rammed earth walls have a texture, colour and feel that is unmatched by conventional building products. From the exterior, they appear to have grown naturally from their local environment, which allows them to retain the connection with the earth from which they emerged.
Internally, rammed earth walls possess their own distinctive qualities of ambience, warmth, and textured finish. Energy efficient climate control is achieved naturally in rammed earth houses, as the walls have a high thermal mass, enabling them to store warmth in the winter and keep the interior cool in summer.
This method, combined with effective solar design, will result in significant savings in heating and cooling energy consumption, while having earth walls as a heat transfer medium instead of mechanically heated air. Additional insulation can also be embedded into external walls to further enhance these benefits.
In short, rammed earth is a tough, green and viable alternative to “traditional” building materials that can provide a unique stamp of originality to a building for those keen to design something new, fresh and different.
We often have to look backwards to go forward. Perhaps the first builders had it right all along – the earth beneath your feet really is all you need.