Introduction To Rammed Earth

A rammed earth building is constructed using a mixture of earth, gravel, sand, silt and clay. The mixture is placed between framework forms and then rammed using a mechanical rammer or hand rammers. Once the mixture is fully compressed, the framework is removed leaving the completed rammed earth wall. The thickness of the external walls is normally around 30cm, but internal walls can be thinner. The framework is setup first, to create the desired shape. The sand added to the mixture helps reduce shrinkage of the wall. The mixture can also be ‘stabilized’ by adding 5 to 10% cement – this is recommended in climates where the wall may be exposed to driving rain. It is important that rammed earth houses are designed in such a way that affords them maximum protection from the rain, such as using substantial overhang on the roofs.

Before the use of cement as a stabilizer, rammed earth buildings common in dry climates. Now rammed earth has building has become viable in wetter climates, either through the use of cement stabilisation, through placing the earth walls within the water proof fabric of the building, or by the applying an external insulation and weatherproofing to the house. The most common stabilisers in Australia are: for rammed earth 6% cement; for adobes 3% bitumen; for pressed earth bricks 8% cement; for poured earth 12% cement.
One of the great benefits of rammed earth houses is the excellent thermal mass provided. A rammed earth wall heats up slowly during the day from the sun’s rays and radiates this heat back out during the night. Earth walls also provide good sound insulation as an added benefit. The downside to the thermal qualities of an earth wall is that they make for poor insulation and so in colder climates extra insulation is often required.

Earth walls have a low environmental impact and require much less embodied energy to create than most conventional building products such as concrete. The walls are very workable, and it is possible to hammer in a nail or screw into them. Any minor damage to the wall can be patched by using the same mixture of earth to give an undetectable fix.

Earth is a natural, durable, healthy and strong building material. It doesn’t require the use of toxic treatment substances that some building materials require.

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