The history and benefits of earth buildings
Why building with earth is undergoing a modern revival and can help create a sustainable future
Earth has been used as a building material for thousands of years. However, in the past couple of decades there has been an increased environmental movement and with that an increase in the status attached to an environmentally responsibly lifestyle.
To meet this increased demand, building materials and designs are moving towards more eco-friendly alternatives. As a consequence of our social aspirations, particularly in the developed world, the construction of modern earth buildings, particularly rammed earth, has increased dramatically.
In the developing world, modern earth buildings have not caught on as it has in the developed world, possibly due to the long history of traditional earth buildings. As the middle class is growing at a fast pace in large parts of the developing world, previously impoverished families and individuals who have spent generations living in traditional earth homes will aspire to live in ‘modern’ houses built from concrete, steel and glass.

Given the numerous challenges of supplying adequate housing in many parts of Africa there is a strong case for trying to find local construction materials that are suitable for housing, such as earth. Building with earth may not cause a reform in housing policy or land ownership but it has the potential to lower construction costs while reducing the environmental footprint of buildings. Furthermore, earth walls provide a high thermal mass, lowering energy costs, particularly in warm climates. Earth, or soil, as a material is used to describe fine-particled materials that originally are from mineral and organic, decomposed products from animals and plants. At the end of their lifecycle, these materials return to form rocks.
There are many ways of building with earth but two major methods are most frequently used; handmade unbaked bricks laid in mortar (adobe/compressed earth blocks) and compacted earth within a framework on site (rammed earth). When constructing with adobe, the earth is first pressed into blocks and then dried before construction use. The advantage of adobe is that the blocks can be made, stored and used whenever needed. For example, the blocks could be made during spring or summer, in order to dry faster and apply surface treatment. They could then be stored to be used in the fall or winter. When building with rammed earth, the entire process, from determining the mixture to construction, is carried out in one go. However more recently there has been an increase in prefabricated rammed earth panels.

Besides balancing the humidity, earth walls also balances temperature due to the thermal mass, a feature that is critical in areas with large diurnal temperature differences.
So why isn’t everyone doing this already?
Building with earth has three major disadvantages, although all of them are mitigated during the construction process. First of all, earth is not a standardized building material. Earth used for building, or loam as it is sometimes called, will be differently composed depending on where it is dug out. In practice, this means that each soil mixture must be investigated in order to know the specific composition and characteristics of the loam. Secondly, the mixtures shrink during the time they are drying, due to water evaporation. The shrinkage size will vary depending on how wet the mixture is, with rammed earth being generally less affected than the wetter mixtures of adobe buildings. Naturally, this shrinkage can be reduced by decreasing the amount of clay and water in the mixture, by optimising the grain size distribution and using various additives.
The third and final major disadvantage of building with earth is that it is not water resistant. The mixtures and buildings must be protected against rain and frost, especially before they have dried. Walls built with earth are often sheltered using roof overhangs or appropriate surface coatings. More recently, natural additives are being implemented to make rammed earth completely water resistant, which is standard for companies such as Earth Structures Group.

Healthy indoor climate by regulating humidity
One of the many advantages of earth buildings is that the material is fireproof. Furthermore, it functions well as a humidity regulator. It is able to balance indoor climate better than any other building material, due to its ability to absorb and desorb humidity.
Research conducted at the Building Research Laboratory at the University of Kassel, Germany, showed that when the relative humidity in a room was elevated from 50% to 80%, unbaked bricks were able to absorb 30 times more humidity than baked bricks, within a two-day period. Further studies done on a newly built house in Germany with earthen walls showed that the relative humidity was a almost constant 50% throughout the year, over a period of eight years, with a fluctuation by only 5% to 10%.
Besides balancing the humidity, earth walls also balances temperature due to the thermal mass, a feature that is critical in areas with large diurnal temperature differences. The earth walls stores heat during the day, when temperatures are high, and releases heat during the night, when temperatures are low. It is not unusual that homes built with rammed earth walls in warm climates require little to no energy for cooling. This characteristic is also crucial to passive solar house design, which is gaining an increased popularity.

In terms of resources, there is generally little need for transportation and production of the material since local earth often is used, which in turn reduces the environmental impact immensely. When earth buildings are no longer needed, the material is simply reverted back to earth, just as it was before. When compared with other modern building materials, the compressive strength of earth is fairly low. This puts structural limits on the material, but is compensated by building thick walls. This requires more raw materials, but is a low cost to pay if the earth is sourced locally.
With modern earth construction, building code requirements for strength and durability are easily met, and exceeded, using admixtures for waterproofing and durability, and stabilisers for strength. With industrial technology allowing for quick construction times, earth walls are re-establishing themselves as the preferred building materials, for humans and the planet.
Originally published at AsaDuru.
