Building with earth is an incredibly ancient construction method but that doesn’t stop it from being fantastic for modern building design. Rammed earth has excellent construction properties being flexible in design and application. It also embodies low-tech building methods.
Rammed earth is formed from loose subsoil, which is moist and compacted in layers. This presses the material to about half it’s original depth and forces the clay in the earth to bond with the aggregate. Because this process is physical, no chemicals are needed. You do however, need a high enough clay content (around 15-30%).
Due to it’s simplicity, this ancient building technique has been popular all across the globe. Cob, adobe and rammed earth were all used historically and these traditional building methods are now being re-discovered by sustainable developers and architects.
Rammed earth, in particular, is becoming ever more prevalent in modern architecture with the growing popularity for sustainable buildings.
There are many environmental advantages to earth buildings. In most instances, construction with earth requires low energy outputs and emits virtually no pollution. This means that rammed earth has very low embodied energy. The embodied energy of brick is six times that of rammed earth!
The thick walls of compressed earth buildings are also extremely fire-resistant; there are no flammable components and everything is so tightly packed there is little chance of combustion. At the other end of the scale, the addition of a stabiliser makes rammed earth resistant to most moisture but continued exposure to water at the top and bottom of earth walls must be prevented.
Earth has benefits for heating as well. It is a dense material that provides high levels of thermal mass, especially when compressed. However, the thermal resistance of rammed earth is very poor so it’s use in external walls is limited.
Rammed Earth: Design and construction guidelines suggests that “to meet thermal performance levels expected of modern energy efficient buildings… external rammed earth walls must either be very thick (over 70cm) or use additional insulation.”
Rowland Keable, co-writer of the book, began building earth structures nearly thirty years ago and now teaches on many natural building courses. He has extensive experience of working with earth, having published Rammed Earth Structures: A Code of Practice. He also established Ram Cast CIC and is a founder member of Ebuk. Clients of Keable’s have included the Eden Project, Big Brother and Bath University.
Building with earth is a great method for construction, especially when other buildings materials are limited. The Whole House Book states that “earth is the most immediate and locally available material it is possible to build with. It is also one of the cheapest and lowest impact construction methods.”
Building with Earth is a three day short course at CAT that gives a thorough grounding in the building method. Designed for anyone that is interested in natural building methods, Keable’s course is very hands on and participants can expect to get muddy!