This is the ninth post in our Super Natural Materials series - you can view the whole series here.

The origins of building with earth

Building with earth is an ancient practice. From rammed earth, to clay, to cob and mud-brick, the earth beneath our feet holds versatile properties and great potential within construction. It's a natural resource that we have in abundance and can be used in so many ways. In this post, we will be focusing on rammed earth and mud-brick. If you haven't seen already, we have covered cob and clay in past #SuperNaturalMaterials instalments.

Rammed earth

Rammed earth is a technique for constructing foundations, floors and walls using natural raw materials such as earth, chalk, lime or gravel. Building with earth – rammed earth in particular – is an ancient method that has recently gained interest again as a sustainable building practice. Simple to manufacture, it's non-combustible, holds thermal mass and is strong and durable.

The compression of ramming earth means that it holds impressive strength – a maximum of 620PSI; this is less than concrete, but more than sufficient for a domestic building. Interestingly, rammed earth can absorb heat during the day and nocturnally release it, meaning that it has a high thermal mass. Of course, earth has low embodied energy and generates very little waste so is a very sustainable material.

Mud

Mud has been used in construction for centuries and is still used to this day, used to coat, seal or adhere materials. One of the most useful and effective ways of building with earth is to use mud-bricks. Also referred to as adobe, this technique means mixing mud with water placing the mixture into moulds and then allowing them to air dry – straw is sometimes used to bind the brick.

The Great Mosque of Djenne (left) is one of the most impressive and well-renowned mud-brick structures on the planet. The World Heritage Site located in Djenne, Mali holds an important role within its community – everyone gets involved.

Locals contribute to the maintenance of the mosque through a unique annual festival. The festival includes music and food, but its primary objective is to repair the damage that has been inflicted over the last year, namely erosion and cracks, caused by rainfall or by changes in temperature and humidity.

Men climb onto the mosque by scaffolding and ladders made of palm wood. They then smear the plaster over the exterior of the mosque to repair it. Due to earth's great thermal mass, the walls insulate the building from heat during the day and by nightfall have absorbed enough heat to keep the mosque warm through the night.

As a building material, earth holds great strength and is extremely durable, which is exemplified by The Great Mosque of Djenne – it's as sustainable as building materials get, a natural material that has low embodied energy but, most importantly, can be used in a variety of ways and has impressive versatility as a material, it can be in the form of mud-brick, cob, rammed earth or clay.

So, why use earth?

• 100% natural, local resource.
• Very low carbon footprint - very little energy goes into the construction of earth, therefore reducing the environmental impact.
• Great for indoor climate - earth has high thermal mass.
• Moisture control - earth can absorb and release moisture meaning that it can regulate humidity - this provides a clean living environment.
• Fire resistance - earth is non-combustible.
• Detoxifying effect - it's a breathable material and has the ability to absorb toxins and smells from the indoor air.
• Affordable - no explanation needed, save some money.
• Life cycle cost - low maintenance: as energy prices rise, efficient buildings will gain more value.
• Zero waste - earth is fully recyclable.
• Climatic control - with its thermal mass, earth manages to even out temperature fluctuations by releasing absorbed solar energy throughout the day, providing a comfortable internal temperature
• Noise control - earth has low sound transmission levels.

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