My first serious encounter of the use of clay as a structural material occurred during the late 1960s when, as an architectural student, I undertook a study of farm buildings in upland Angus. Until that point my awareness was limited by a lack of knowledge and understanding. Hitherto, clay had only been recognisable as a structural material through illustrations of vernacular buildings from the middle east and it took me some time to recognise what the mortar materials were in the partially collapsed buildings that I was studying.

With a greater understanding came the recognition that, in addition to vernacular buildings, a broader use of earth structures were also to he found in major architectural and civil engineering projects.

As an international material, earth provides the ultimate “green” construction substance. However there remains a considerable amount of professional ignorance and misunderstanding of the material. And, with so many other traditional construction techniques, we are currently in the process of having to relearn much of what we were once familiar.

Survey and analysis can help, but the best experience will be gained from undertaking experimental work in connection with historical studies. In an attempt to relearn some of the lost techniques Historic Scotland initiated an experimental earth structure research project in 1996. At three sites around Scotland (Culzean, Battleby and Fort George) test walls and panels have been constructed. These will enable us to monitor, over time, weathering mechanisms, moisture movement and sinkage.

Inevitably, such an approach is a great simplification of what was an infinitely variable use of the material around the country. But it will enable us to start exploring this significant material in a serious manner. Through relearning from analysing emerging faults, and the techniques used in undertaking the building and repair work, it is anticipated that we will eventually be able to offer a greater under-standing and awareness of the traditional craft skills required to effectively work with the various mixes.

This Technical Advice Note, the sixth in the series, attempts to provide a preliminary look at what the material is, and how it was used. It also tries to set the scene in such a way that earth, in all its forms might he used to a greater extent in the future. Through building upon the knowledge amassed through Dr Walkers long standing academic studies, and practical Historic Scotland case work experience, the intention is to help professionals, and education and training providers, working in the field of architectural conservation in Scotland gain a better understanding of what is involved.

It is also recognised that the TAN’s content will have an international significance. Perhaps, for the first time, this will enable the Scottish perspective to be taken into account along with that from other countries where a greater understanding of the material is much more acute than here.

INGVAL MAXWELL Director, TCRE