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Interview of Hugo Houben

Mr. Hugo Houben, physical engineer, is a researcher at the Ecole Nationale Supérieure d’Architecture of Grenoble (France), founding member of the CRATerre laboratory and responsible for the "Scientific and technical knowledge" theme. He has been teaching for 30 years and his career is largely dedicated to earth. He is author and co-author of several articles and books among which the Traité de construction en terre which has been translated in several languages. We met him in Bamako, during the Terra 2008 conference.

Africa is host for the first time to the international conference on the study and preservation of earthen architecture (TERRA 2008). What do you think of this?
First of all, I think that it is really great to have it in Africa. Who would have dreamt of it ten years ago? I am really pleased particularly since there are now partners to help us: Africa 2009, EPA and its Anglophone equivalent. It is legitimate and cannot be but appreciated. The second thing is that in this particular issue, there is an enormous part dedicated to cultural continuity. It is an issue which appeared ten or fifteen years ago and for which all those who have worked on it may have found theoretical answers. Whereas here, with the examples of Djenné and Bandiagara which have been shown to us, we can see that there are first faltering steps. Now we must work hard to insert them in the long term. The evolution is already in progress and we must go beyond tradition in some cases to transfer it to urban contexts. Of course when we talk about Djenné we are in an urban context, but I am speaking of large capital cities like Bamako. I have good hopes that it will work.
The other thing is that I have never heard in any preceding TERRA conference so much stress on the fact that "there is no conservation of earthen architecture without transmission of traditional knowledge". No architectural conservation tradition without the total commitment of the culture to which the architecture belongs. These are very important things that already existed in talks but are now being carried out.

You explained that you went from two main lines of work - one on building and one on conservation of cultural heritage, to one line of work. How did you merge these in order to have only one perspective?
I think that we have not yet totally succeeded. The issue comes from the PAT courses (Preservation of Earthen Architecture) the last issue of which was incredibly well organised. The techniques used in this area (the earth material, various techniques, laboratory tests) which are based on the knowledge circulated by CRATerre for the past twenty years, are modern techniques despite their use in conservation. I can make adobe today but I must insert it in a wall which is a thousand or two thousand years old. Must I do it? I know the technique for making blocs of compressed earth. Must a conservator learn to make blocs of compressed earth? Must one teach him to make adobe today when eight thousand years ago it was made differently? All our knowledge is of today, that is to say it comes from contemporary building. In fact, the different steps of life cycle which go from pedogenesis to geology, to quarry and then to architecture are very well known and easily transmittable. But the conservator who is confronted with a two or three thousand year old building thinks differently. How is it built? What is its structure? What were the materials?
We see that in the end, we do not know much or we do not know how to transmit anymore because there are not enough experiments, and above all, not enough codified experiments which are transmittable within an academic or professional education system. We therefore asked ourselves how to transmit to students and professionals something which will enable them to make good decisions on a conservation field, without them having had prior knowledge of this type of situation that even teachers do not know. The answer is that 'to hunt a lion you should think like a lion'. So the next question is to know how a lion thinks. So in order to build with earth, you need to think like earth. But how does earth think? It is a material made of grains. Therefore, one should transmit a whole general knowledge on how the grain material behaves and we try to bring it as close as possible to architecture. So we have a basic input from which students take theoretical and practical parts from all that concerns conservation and building, because there is much more experience. In between, we teach them how to become lions, that is to say to react with their guts. That is how they get to understand how the earth reacts.

Do we have proof that it works?
Since we have been teaching this programme, there have been already three new methods for building with earth which have been invented. Students are currently working on them. Two of them will be part of a research programme to refine and promote them among companies so that earth becomes a very widespread building material. There is another method in which I am particularly interested. It was conceived by students who have understood how earth reacts. It is used in France, especially in Grenoble, for a building system that is totally compatible with the problems of tramps who live on the streets and who do not want permanent shelters because they feel imprisoned in them. We do everything with them and in a day they manage to build a shelter which has a very high performance in winter because it does not need to be heated. This is possible only because students now have grains in their guts. Which frees them completely from existing technologies so they can answer to constraints. Even if scientifically one could believe that such a system is fragile, if we understand the way grains work, we get to the conclusion that such a shelter does not collapse at all. It a system mixing earth and wood which does not need screws. Only a few boards, not necessarily well cut, which are piled up and on which one throws bucketfuls of earth. And it works! I often wondered if we should not do an evaluation with the students to know if this programme brought them anything, but we have the proof that our students have invented three new building techniques.

Thank you very much.