FROM EARTH TO VALUE

Preconceptions about earth

by Erik Pelicaen

Once, along with wood and natural stone, earth was the only material to build sturdy constructions with. However, the natural raw material is losing out to brick, steel, and concrete today. Given that circular construction is necessary to counter climate, waste, and resource problems, earth construction is experiencing a revival. However, there is a lack of confidence in the material which limits its application in our regions. Therefore, this article debunks some of the prejudices it still faces today.

Among the general public, earth or loam construction is often associated with a primitive way of building somewhere in the Global South. That judgment implies that the Western or industrialised way of building is a whole lot better. But is that really the case? Certainly not in terms of environmental impact. Unlike building with steel and concrete, traditional earth construction contributes little to global warming and to the depletion of raw materials. In addition, when an earth building is demolished, it can be recycled or composted and thus does not become waste. Since no planet B exists and the construction industry is responsible for the lion’s share of global CO2 emissions, waste production, and resource consumption, we need to rethink our Western building culture and deploy regenerative building materials.

Earth does not undergo a combustion process or chemical transformation as with brick or cement, which means that much less energy is needed to produce earth-based building materials and, therefore, less CO2 is emitted. The absence of a firing process also ensures that the original raw materials can be obtained again after the demolition of earth buildings or that the earth can be returned to nature. In addition to the possibility of reusing or naturally decomposing earth, it is also widely available. The excavated soil, regarded as waste when laying foundations, can be valorised and transformed into earth-building products. Geologically, soil suitable for earth construction is also an abundant resource in the Earth’s crust. In addition to ecological benefits, earth has many pros related to well-being, health and comfort. For example, it offers good indoor air quality thanks to moisture-buffering properties and can guarantee a pleasant indoor climate thanks to its high thermal inertia. Although several examples of modern earth-building applications exist in our region, a real breakthrough is still lacking. Sceptics are mainly concerned with the lower strength of earth as a building material, its sensitivity to water and maintenance, lack of standards, and higher implementation costs. The following are some typical statements that prevent the upscaling of earth construction.

“Earth is a weak material”

Earth is one of the oldest building materials in the world. In Turkey, for example, one can still find remains of the first human settlements made of earth and wood, about 6,000 years old. One of the most iconic examples to refute this prejudice is the village of Taos Pueblo in New Mexico. Entirely built in adobe (sun-dried mudbrick), the village is nearly 1,000 years old, and about 150 people still live there today. Every year, the buildings are given a fresh layer of earth plaster to protect them against tornadoes and hail storms that are common in the region. Moreover, earth has not been limited to single-storey buildings throughout history. The city of Shibam in Yemen, also called the Manhattan of the desert, consists of several meters-thick adobe buildings up to eleven floors. Dating back to the 16th century, 7,000 people still live there today. Even in our regions, numerous examples still show that earth is quite a solid and resistant material: in the United Kingdom alone, one can find more than 500,000 buildings. However, the Industrial Revolution halted that tradition: brick, steel and concrete could suddenly be produced cheaply on a large scale. Because these are more robust and water-resistant materials, earth-building techniques fell into oblivion. Today, however, there is an overkill tendency: ultra-strong and water-resistant materials are used for applications for which those requirements are unnecessary, such as infill masonry made of concrete blocks and cement mortar. Earth CAN be used structurally and exposed to the weather but may have even more potential in self-supporting and dry applications such as partitions, flooring, or wall finishing. For example, earth plaster is probably the most common application in Western Europe.

“Earth is not a modern material”

Since it has not lived a similar history of standardisation, earth construction is technically lagging behind brick and concrete. However, earth as a raw material can be found almost everywhere. Earth construction has been present in all continents long before the Industrial Revolution. It is actually still one of the most popular building materials today: more than two billion people live in buildings made of earth. Of course, the majority of these are located in less industrialised countries, usually with a dry climate. However, also in our regions, earth construction is increasingly emerging. L’Orangerie in Lyon, France, is a fine example of modern earth construction. By working with compression arches, the architects made logical use of the fact that earth is weak in tension. The rammed earth blocks were prefabricated, which ensures a higher quality guarantee, and the site is not subject to weather conditions. However, to get this project built, the architects, after lengthy negotiations, had to use almost three times the usual safety factor for concrete structures. The struggles show how little confidence there is in earth as a building material. The Ricola Kräuterzentrum in Switzerland by architects Herzog & De Meuron also has a similar story. Although the well-known earth construction pioneer Martin Rauch tried to convince the architects that the building could be constructed entirely of load-bearing rammed earth blocks, the famous duo nevertheless opted for the safe solution of a concrete skeleton structure with rammed earth blocks as an infill.

“Earth cannot withstand water ”

A common technique to make earth water-resistant is to stabilise it with lime or cement. However, this happens at the expense of the environmental impact and the circular benefits at the end of the life cycle. However, buildings made of earth CAN survive in wet climates. In Weiburg, Germany, a six-floor high apartment building in rammed earth from 1830 still stands today. How? By applying the correct design principles. Of course, precipitation or groundwater can damage raw earth buildings, but through thousands of years of empirical validation by trial and error, we have learned how to prevent that with specific building techniques. Our region’s classic principle for earth construction was to design with ‘a big hat and strong boots’. In other words, an overhanging roof that protects the facade against precipitation and a stone foundation that protects the walls against rising moisture. Finally, water also ensures that earth can become plastic again after hardening – which no other building material can do yet. As a result, on the one hand, wear and tear can be repaired more efficiently and on the other hand, the connections between earth and other building materials are reversible and therefore promote reuse. At the end of the life of buildings made of brick masonry, for example, it is difficult to separate the cement mortar from the bricks. Therefore, bricks are often not reused or recycled and instead simply dumped. Can clay brick masonry provide an answer to this problem? Finally, water also ensures that earth can become plastic again after hardening – which no other building material can do yet. As a result, on the one hand, wear and tear can be repaired more efficiently and on the other hand, the connections between earth and other building materials are reversible and therefore promote reuse. At the end of the life of buildings made of brick masonry, for example, it is difficult to separate the cement mortar from the bricks. Therefore, bricks are often not reused or recycled and are disposed of in landfills instead. Can earth block masonry provide an answer to this problem?