It is a construction technique that has stood the test of time for thousands of years and, to this day, continues to be used by various countries around the globe. To help paint a mental image for you, the Great Wall of China is one such landmark of colossal scale which owes its thanks to rammed earth building. At the other end of the spectrum, this technique is also used for both affordable housing solutions around the globe, as well as upper-class, wealthy domestic projects. Before we take a look at how it’s used in modern building and construction projects, let’s go back to its origins.
Traditional rammed earth
With origins tracing back thousands of years and from different areas of the world, rammed earth was traditionally comprised of clay-rich soil, water and naturally sourced stabiliser, such as plant fibres, bitumen, or animal urine. This mixture was then compacted within temporary formworks and allowed to set and harden in the sun. Once this has been done, the formworks can then be removed to leave behind a remarkably durable and robust structure capable of withstanding compressive forces up to 2.5 mega pascals (roughly 10% of the compressive strength provided by the average modern brick).
This method was used to create walls, roofs, floors, fireplaces, ovens and even furniture. These structures could also be reinforced with embedded bamboo grids, or timber beams. The earliest evidence of historical buildings having used this method are present in China, South America, the Middle East, India and North Africa.
Modern day popularity
Fast forward to today and we can see an increased popularity in rammed earth building techniques over the past three decades. Australia in particular has seen an especially high interest in cement-stabilised rammed earth (CSRE), which utilises a mix of cement, low-clay soil and water.
CSRE still involves the traditional method of being left to dry in temporary formworks, however it offers a significantly higher resistance to compression forces up to 40 mega pascals. This degree of durability means that structures built using CSRE usually don’t require special protection from natural elements as they are strong enough on their own.
Benefits of using this building technique
There are numerous advantages to using rammed earth building from both a consumer and builder’s perspective. Not only are the construction materials much more economical to source, but they can also be sourced locally, reducing the added cost of transportation. The building technique itself is very straightforward, meaning only one or two experienced builders are required on-site to instruct the labour crew how to mix the materials and construct the formwork. Depending on the project, the manual work can usually be completed by unskilled or untrained individuals from the local community, further reducing costs and generating employment opportunities. Other benefits include:
- Fire resistant
- Controls humidity
- Rot & termite proof
- Weather resistant
- Superior durability
- Environmentally sustainable
A sustainable and renewable solution
As the main ingredient in both traditional rammed earth and CSRE is soil, it is easily obtainable and can be reused, or recycled once the structure has reached the end of its life (which can often span hundreds of years depending on the structure). This can dramatically influence the amount of timber required in the building and construction industry and help limit environmental concerns such as deforestation.
Additionally, rammed earth also has fantastic insulation properties, as the walls are usually quite thick (around 250-800mm). This means they can actually produce some very energy efficient indoor living conditions. This is especially beneficial in hot, humid areas, where keeping cool air contained inside is a constant struggle. This particular building material also breathes, making it great for humid environments and those with respiratory problems.
So why aren’t more people using this method?
Considering all of these very compelling benefits, why aren’t we seeing more structures built using this technique? While it may have been around for thousands of years, the fact of the matter is that our knowledge surrounding this method have only surfaced in recent times. Our ancestors used such methods for their convenience, low cost, and natural strength, but they had no idea as to the environmental benefits (and most likely wouldn’t have cared for such information).
As awareness grows however, we can expect to find more and more consumers looking to have their homes, businesses and other structures built with this convenient and natural technique.