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Often the earth used for mud bricks can be mined from a building site itself, or if not, then usually from close by. A wide variety of earth types are suitable, and once mixed with water to produce a mud, wooden or steel moulds are used to form the bricks. After baking in the sun to harden,the bricks are ready for laying. Depending on the climate, this can take between 2 and 4 weeks.
Using the identical mud mixture for mortar, the bricks are laid in the conventional way. Paradoxically, the majority of informal dwellings in South Africa are built of earth, and the task of the Australian team is not to introduce earth building but to modify the process.
Two major flaws in traditional South African earthbuilding have given the process a bad reputation. First, in an attempt to reinforce mud walls, untreated wooden poles are added. In the short term this "composite" has strength, but over time termite infestation destroys the timber armature and the structure collapses.
In the second case, solid mud brick walls fail due to the ingress of water into the brick, causing the clay component of the brick to swell and then shrink upon drying. This action causes cracks, and ultimately the structure falls.
One of the key elements in the Australian approach is the addition of a stabiliser (in this case asphalt emulsion) into the mud mixture. Costing a fraction of the price of cement, the asphalt emulsion completely waterproofs and also increases the compressive strength of the brick.
Drawing on the long history of Australian Earthbuilding, the AusAid team is busy negotiating with South African Universities, Technical Institutes and Standerds Authorities in an attempt to codify Earthbuilding practice in South Africa. Although the actual construction process is simple, and in fact more user-friendly than conventional building, success hinges on an understanding of the opportunities and limitations Earthbuilding presents.
The huge cost advantage of building in earth makes it perfect for South Africans needs, but there are other factors which have popularised Earthbuilding worldwide. The thermal and phonic qualities of mud brick have found fans in affluent areas of America and Australia where an awarness of green issues prevails. While it is difficult to dislodge cost as the reason for choosing earth, the Australian team is pushing hard for mud brick to be accepted as a whole concept, with equal importance placed on environmental factors, energy conservation, and the potential for owner building.
Because of the forgiving nature of mud brick, it is far easier for the novice to build a structurally sound dwelling in earth rather than in fired brick or concrete. This accessibility to the medium may well be the lynchpin of the project's success. Homeless South Africans have at the very least their labour to contribute. Training is a high priority in the project.
durbanet
