Rammed Earth
​Rammed earth is a building technique where an earth mixture is layered into formwork and compacted. After removing the formwork, the self-supporting wall hardens in the air.
Rammed earth impresses with its extreme strength and high density of 1,700 to 2,200 kg/m³. The material can withstand compressive forces and is therefore suitable for both load-bearing and non-load-bearing walls as well as seamless floors. Particularly remarkable is the possibility to create curved structures, provided the compressive forces are distributed accordingly. The coloring can vary depending on the composition and can be further refined with earth pigments. When properly executed, rammed earth buildings are extremely durable and maintenance-free for years.
A Look into History
Rammed earth has been used in construction for thousands of years, with evidence dating back to the Neolithic period. The technique was particularly widespread in China, where it was used for both ancient monuments and vernacular architecture, including the Great Wall. The Romans and Phoenicians brought the technique to Europe. During the Moorish rule in Spain, structures like the Alhambra were built, which still stand today. This tradition continues in regions like Africa and the Middle East, where desert communities and Berber tribes still use rammed earth.
The Material
The foundation is an earth-moist and finely crumbled mixture that becomes extremely hard after compaction and drying. The ideal rammed earth consists of approximately 50-75% gravel and sand and 20-35% silt and clay. Since the required components - clay, sand, and gravel - are often found in nature, a large portion of excavated material can be used directly. In many countries outside Europe, lime or cement is often used as a binder, which can, however, impair the climate-regulating properties.
Building Method and Application
The construction involves several steps:
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Setting up stable formwork
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Filling in the earth-moist material in 10-15 cm thick layers
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Compacting each layer with special tools (manually or mechanically)
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Immediate removal of formwork possible (no setting time needed)
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Complete drying before applying loads
