Earthen architecture

Materials, techniques and knowledge at the service of new architectural applications

by Hugo Houben and Hubert Guilland.

A major building material

The importance - both in quantity and quality- of unbaked earth constructions in the world is very little known. Believed to be of ancient origin, (it is associated with the early civilisations of the Nile, Tigris and Euphrates, Indus and Huang He), nowadays, earth is not usually regarded as a major building material. This is despite the fact that it continues to leave an undeniable and distinctive imprint on the architectural landscapes, both rural and urban, of many countries. Unbaked earth is still, in fact, a major building material, being used extensively by people to erect homes and other buildings. Although sites of human occupation have seen constant regeneration with the passage of time, unbaked earth construction has persisted. Excavated from the soil itself, and moulded by the hand of man (or trampled by beasts of burden), the result is a building material which is used in all forms of construction-from simple huts and modest homes, to farm buildings, large houses, urban blocks, religious edifices, castles and palaces. The skills employed are based on knowledge acquired and refined over a long period of time.

A contemporary building material

While the use of earth in so called 'advanced' countries has declined in the 40 years since the end of the Second World War, in the developing countries it has continued unabated. In the former, the industrialisation of construction and other sweeping changes have rendered obsolete ancient techniques based on the use of local skills and materials, and on mutual help within communities. In the latter, various factors have dictated the continuing use of locally available solutions, materials and knowledge. These include shortages of processed materials (which are costly in both foreign currency and imported energy terms), the widening of the development 'gap', the accumulation of debt contracted within the international monetary system and the survival of local life-styles in which people are accustomed to coming to get her for mutual help for survival. In these countries, which have no industrial means, and which are to be found in various latitudes across the world, earth remains the main-if not the only- building material. Do these circumstances mean that it is a poor material, fashioned using outmoded techniques and unsuitable for promoting the development which is so necessary? The answer to this question is a clear 'no'. On the contrary, the materials and techniques involved are generally of a high standard. They can ensure true architectural quality, allowing communities to continue creating their private or public living environments, and to integrate their buildings into a coherent framework of self-generated development which makes the most of the resources available, both human and material. In fact, scientific and architectural research into earth as a building material, and on related building techniques, has made considerable progress in recent decades. Combined with investments made by industrialists and construction companies, the result is that we now have a wide range of properly mastered production procedures and technical solutions available. These offer great flexibility in meeting a wide range of possible applications.

Making a mark on world architecture

Recent global surveys, although partial (covering about 30% of the world's housing), have given us an indication of how extensively earth is used in construction. In developing countries alone, 50% of the rural population and 20% of those living in urban areas are believed to be concerned. The figures, which are drawn from the combined data of statistical surveys in various areas, and from bibliographical information, almost certainly underestimate the true position. They show, for example, that 60% of the housing in Peru is in moulded bricks or rammed earth. 83% of the houses in Kigali, the capital of Rwanda, are made of earth. More than 70%of India's housing stock is constructed out of moulded earth bricks or using successive layers of earth, and these buildings provide shelter for nearly six hundred million people. In France, many rural dwellings are built from unbaked earth and one finds, for instance, that in the Dauphine region, up to 90% of the buildings in certain villages are made out of rammed 'pise' earth. Finally, in California, there were estimated to be almost 200 000 'adobe' (sun-dried earth brick) dwellings by 1980 and the use of this material was growing at the rate of 30% a year.

Closer examination reveals that the whole world bears the indelible stamp of earthen architecture. Earth is used in Africa-in humble shelters built on leased land and in the great granaries of the continent. It is found in the palaces of the Hausa emirs of Nigeria, the ksours and kasbahs of Morocco and the mosques of Mali. In the Middle East, you come auoss it in the tightly-packed neighbourhoods of Ispahan and Iran, the fortified dwellings of Najran in Saudi Arabia, the multi-storey earth blocks of Shibam and the valley of the Hadramaut in Yemen. In Europe, there are the mouded brick farms of Aquitaine and the baroque and neo-classical castles of the Saone valley. And bringing in other parts of the world, we might mention the pueblos of the New Mexico Indians, and the houses built by the Hakkas in the Chinese province of Fujian, laid out in their characteristic concentric circles. The use of unbaked earth in building may be seen as a vestige of past history, but it is actually a living framework for history in the making.

Realistic uses for the future

Confronted with the energy crisis of the 1970s, oil-dependent industrialised countries were forced to look again at tried and tested technical solutions which were now proving to be too 'energy-greedy'. The building sector did not escape this reappraisal and the search began for ways of reducing energy consumption both at source (covering the production and use of building materials) and further down the production chain (maintenance). Research on biomass and solar energy ran in parallel with experiments to update traditional materials and to attempt to rationalise the production process. Earth again became a focus of interest, with government institutions supporting a considerable amount of new research and experimentation. This covered applications in both the industrialised world and in developing countries, research for the latter being undertaken in the context of bilateral or multilateral cooperation. With the threat to the ecological balance posed by pollution, degradation and the plundering of natural areas, this interest in developing materials and techniques that are inherently friendly to the environment has not lessened. In many places, people are becoming increasingly involved in controlling and managing their living environment. The field has been opened up by qualitative research, a new awareness of the available options and an increase in leisure time. With techniques now at hand that are easy to use and economical, a greater measure of (partial or complete) selfhelp building is now possible. The USA, Australia and Germany all encourage new forms of intervention in building which give greater responsibility to the occupier in the creation of his living environment. Viewed from this perspective, earth as a building material has definite advantages and plays an important role.

In developing countries, burdened by debt and confronted by an urgent need to build on a scale unprecedented in history, imported materials, techniques and energy are largely inaccessible to the majority of people, and their use may contribute to promoting 'bad' development. Building with earth emerges as an efficient shortterm way of producing houses or public buildings such as schools, which are both economical and of high quality (being culturally and climatically suitable). Decision-makers in these countries are well aware of this and have mobilised 'upstream' feasibility studies in their education and public housing programmes. The research covers local resources and knowledge, and the use of labour intensive techniques that generate employment and enable the population gradually to become 'monetarised'. The days of costly experimentation, often with no practical result, are now over. A new confidence in the resources that are available must be encouraged. There needs to be an increase in building completions and those who built them need more training. Today, this is happening in Mexico (850 earthen houses recently built in the state of Zacatecas) and in Burkina Faso (6000 school classrooms constructed by 1995.) No fewer than forty million homes will have to be built between now and the year 2000 for the urban population of Africa alone.

Studies show that for most of the people involved, there is no choice but to employ local materials, most often earth. One can thus predict that at least 20% of urban and pert-urban housing in African countries (about eight million units), will be built in earth over the next ten years, at a rate of eight hundred thousand units per year. If demand from rural areas is added to this, one gets some idea of the scale of the task facing decision-makers and builders. The use of earth and other locally available materials is unavoidable, and should be encouraged.

Environmental advantages

It is particularly important to enumerate the many advantages of building in unbaked earth from the point of view of the environment. This issue, one of the contemporary problems facing society, is increasingly moving centre-stage, and in the future, it is sure to play a greater part in political, economic, social and cultural strategies linked to the planning and improvement of the quality of life. Here we refer to the concept of the environment in the widest sense of the word, ecological, economic, technical, health-wise and psychological, cultural and human.

From the point of view of the ecological environment

In terms of pollution and degradation, unbaked earth offers a highly positive picture:

- It does not contribute to the deforestation which results, for example, from the use of organic resources for firing baked earth materials.

- It does not consume any nonrenewable energy (oil, gas, etc.) at source for the processing and production of materials, or further down the production line in their application. This is in sharp contrast to the production of cement, lime and other conventional binding materials, and steel.

- By exploiting strata on construction sites, it allows a considerable saving in energy for the transport of materials.

- It does not contribute to a degradation of the landscape as does the extraction of minerals and ores which hollows out hillsides and creates open cast sites. A great deal of the earth excavated in the course of large public works (notably roads and motorways) can be recycled and used in building (allowing very easy decentralised distribution).

- It does not contribute to the diminution of resources of aggregates such as gravel and sand, excavated either from quarries or from water courses, in insular sites or lagoons. The latter can endanger the ecological balance of these natural environments.

- It uses very little water which is essential for the life of the people.

- It produces no industrial or chemical waste and has the additional advantage of being almost entirely recyclable.

From the point of view of the economic environment

- It is often comparable in cost with, or indeed more economic than competing technologies and requires no major financial mobilisation for its generally light production infrastructure.

- It guarantees rapid amortisement thresholds for bankable investments thanks to its low infrastructure requirements for usable production.

- It contribution to local flexibility, being readily susceptible to a decentralised approach.

- Throughout the production process, it creates employment and monetary added-value which can be injected for development purposes into other sectors of the economy.

- By allowing savings in energy and foreign currency, it contributes at the macro and micro economic levels of the building sector, to a considerable reduction in developing countries' debt and to the balance of payments.

From the point of view of the technical environment

- It has thermophysical and hydric properties (good conductivity, energy retention capacity, thermal differential, delayed temperature differences etc.) which help ensure comfortable temperatures:

- It normally only requires simple production and application tools (moulds, presses, light shuttering, normal masonry tools, etc.) which are widely accessible to masons and self-help builders.

From the point of view of health and the psychological environment

- Not only non-polluting in its use, it also guarantees the absence of harmful effects in the context of daily life (no gaseous emissions or other toxic chemical components, radioactive emissions etc.)

- It contributes to psychological wellbeing by the architectural exploitation of its inherent characteristics; these include the surface texture, colour, form and luminosity of the material. It thus makes an active contribution to the beauty of the living environment.

From the point of view of the cultural and human environment

-It maintains the traditional architecture heritage of the area in question through the use of local materials and thus plays a part in the respect for, as well as the survival and updating of, cultural, architectural and urban environments.

- It allows local populations to take charge of the production of their built environment and thus contributes to the expression of the democratic rights of all to control their living environment.

The future of earth on the move

In her work entitled 'A Fate Worse than Debt' (Penguin Books, 1988), the famous political commentator, Susan George, analysed the debt situation of developing countries and attempted to determine the basis for a positive resolution of the problem. Her approach focused in particular on solutions involving repayment in creative values or 'in kind' rather than in strictly monetary means. At the end of her analysis, she put forward eleven potential solutions to allow this repayment in kind and to launch a coherent approach for the development of less advanced societies. One of these recommendations was that it would be necessary to develop 'the study and survey (and if necessary the improvement) of local building techniques, in particular earth architecture ('pise' or 'banco').' Ms George argued that new buildings, particularly public ones, should be constructed using these techniques.

It is clear that various solutions are being considered for the future: one in which building with earth, using a wide range of local techniques, will have a new technological, social, cultural, ecological, economic and political role of paramount importance.

Various methods of utilisation

The technical, constructional and architectural possibilities of earth are very extensive. The study of popular traditions and of traditional knowledge throughout the world has enabled some 18 different methods of utilisation of the material to be identified, each in itself capable of being applied in a wide variety of ways. This wide construction potential has enabled the building of modest shelters, village houses, urban blocks, religious edifices and palaces. This is not to say that other traditional materials do not have an important role, but the sheer diversity and flexibility of earthen architecture probably cannot be equalled.

As was indicated earlier, the use of earth as a building material has given rise to numerous applications using a wide variety of production and construction techniques. Some of these techniques are still used in traditional construction many countries, some have been abandoned, while others have only recently been the subject of developmental experimentation. It is worth noting that there is a register of the principal techniques, mainly associated with processes using moulds, shuttering and direct shaping. The six most widely used techniques are: 'adobe', 'rammed earth', 'straw clay', 'wattle and daub', 'cob' and 'compressed blocks'.

Of these six, three (wattle and daub, straw clay, and cob), are highly traditional, while the others (adobe, rammed earth and compressed earth blocks) have recently been the subject of spectacular evolution linked to the modernisation of production machinery and methods of application.

The use of earth