When Hannibal crossed the Alps with his army and elephants to wage war on Rome in the third century BC, he introduced rammed earth construction into Europe by building watch towers for his men.
A little more complicated than mud pies, but using essentially the same materials, it is a building technique with roots deep in the history of civilisation.
Modern day rammed earth construction uses soil with a suitable particle grading of gravel, sand and clay, blended with a small percentage of water and cement, (around 10 percent, to act as a stabiliser). This mixture is compacted in steel-frame and plywood forms to produce a high density material that has excellent structural strength and distinctive character.
Walls are cast in panels, which inhibits cracking, and keyed together. They are waterproof, load bearing, absorb noise, are relatively maintenance free and naturally breathable. Their standard thickness is about 300mm, and they can be left in their natural state. Between 100-150 tonnes of compacted earth can be used for an average house.
Earth buildings are cool in summer and warm in winter, due to the temperature stabilising properties of their thermal mass. The beauty of earth houses is that they are one off designs that blend naturally with the environment and look as though they grew out of the ground that stand on.
As people are generally becoming more aware of the good feeling of living in an earth home, and taking note of the environmental benefits, so the popularity of earth building is increasing. Other benefits are that the natural earth can often be taken from the site where the house is to be built thereby also saving in transport costs, and giving a sense of "local identity".
From a comfort point of view, rammed earth buildings, in common with other earth buildings, stated by Professor Rogers of Melbourne University, Architecture Department, have a "much higher quality of space about them than the same space defined by conventional materials". This widely recognised benefit so capably described by Professor Rogers is the well known feeling of "wellness" or "good vibes" that so many occupants of earth buildings have described over the decades. Earth buildings have been described as low toxicity and allergy free. Earth walls have colour, texture and "feel appeal" that is rated highly desirable by most occupants. The tactile attractiveness of most earth walls is very widely accepted. It is no surprise that many building biologists worldwide often favour earth as a building material over other building materials. The sick building syndrome is not linked to earth buildings.
The Faraday Cage is notionally an electrical conducting surrounding box the size of a building which can generate electro magnetic fields, the so called EMF effect, which are unpleasant to humans. A steel box or steel framed house can generate low level electromagnetic effects as it sits on a site, as in reality it is moving through the earth’s weak magnetic field. Such effects are said to not exist with earth walls. The Faraday cage phenomenon is being studied by building biologists and those seeking the best living environment. Further and more decisive research is required in this area to clarify and quantity what is said to be a big advantage of earth buildings over conventional buildings.
The thermal properties of earth walls are highly desirable, having a very high thermal mass at reasonable cost. The inhabitants of nearly all well designed earth buildings continue to be pleased with the comfort afforded by such buildings largely due to the high thermal mass evening out the day time/ night time temperature fluctuations. This effect is commonly known as the "Thermal Flywheel". Rammed earth has a good balance between thermal transfer (R-resistive) insulation (U Factor) and thermal storage (capacitive) insulation (Thermal Mass). A good balance of these properties is required for year round comfort in a house. Earth has this balance whereas most other conventional building materials do not.