What is Rammed Earth?
A rammed earth house is one which has been constructed by the process of placing natural earth, mixed with other (natural) loose material, into forms or "moulds" and compacting them to such a degree that they become self supporting and capable of supporting roof structures above them.
The remains of rammed earth buildings built over 2,000 years ago are still visible in parts of China. Until recent times the construction of rammed earth buildings was extremely labour-intensive and the ramming was carried out by human effort and strength. Today, mechanical rammers and tampers are available so the work can be carried out more quickly and efficiently.
How are Rammed Earth buildings constructed?
The technique is simple. First, two strong vertical frames are built and the distance between the two internal faces is the thickness of the wall to be built. This frame is the equivalent of formwork or shuttering in concrete work.
The material used in the composition of the work is usually earth mixed with sand or gravel. This mixture is dampened and placed inside the support forms in layers of approximately 200mm thick. Each layer is then rammed and compressed to about 100mm thick – about half of the height of the un-rammed layer.
This process is continued layer by layer until the required height of the wall reached. At this point the forms are removed and the section of the wall is complete. The forms can be removed immediately after the top layer is rammed because, unlike concrete, there is no setting time involved and the binding of the materials is done in the ramming process.
The wall is ready for immediate load-bearing use and a conventional roof can be installed straight away. Patching up any defective areas can be carried out using some of the mixture placed in the wall itself. In the same way decorative designs and can be worked on to the wall faces by applying a thin coat of the mixed material and creating patterns on it.
The walls have good soundproofing qualities and are insect and fire proof together with excellent insulation properties. Almost any material can be mixed in with the earth – cardboard, steel bars and stones can all be used, but the earth itself must be the main ingredient.
The only material that would not be welcome into this type of project is cement, although it could add strength to the walls. Cement is regarded as eco-unfriendly because of the amount of carbon emissions created in its manufacture.
No lintels are required in a rammed earth building – the door and window openings are just cut out of the new walls. If the ramming has been carried out thoroughly the walls can be buffed up with a wire brush to produce an attractive natural finish.