Historical precedents
First-hand observation of rammed earth structures in the Rhone Valley in southern France suggests that buildings constructed of natural soils without the addition of portland cement can achieve service lives of well over 250 years. Nearly all of the traditional earth structures visited in the Rhone Valley were built with unadulterated soil taken directly from the building site. Many residences and agricultural buildings are still in use in this region in varying states of repair. Observation shows that roof leaks and shear stresses at the corners of structural rammed earth buildings account for the majority of failures. Regional builders have developed methods for coping with degradation of rammed earth, although construction and repair of rammed earth structures is in danger of becoming a lost art in the region. Important work is currently carried out in construction and preservation of rammed earth structures by CRATerre, a research group at the University of Grenoble. The group, which the the author visited while performing research in the region, maintains an archive of rammed earth structures and trains students in the theory and practice of building in a variety of earthen methods.