Earth to earth: Patterns of environmental decay affecting modern Pisé walls

Rammed earth/pisé is an earth building technique with a deep history in several countries across the globe. In the past twenty years, pisé buildings have seen a resurgence in popularity, primarily because of their environmentally friendly, passive energy characteristics, but also due to the aesthetic appeal of the fabric. As with all other earth architecture, pisé is susceptible to decay by moisture ingress. This paper presents longitudinal observations on the decay of capped and uncapped pisé walls of an early twenty-first-century complex of four buildings in Albury (NSW, Australia). It can be shown that while surface treatment with water-repellent sealants prevents the ingress of penetrating damp, it also traps moisture (falling damp) in the fabric by restricting evaporation. This leads to internal cleavage between the consolidated and the unconsolidated fabric and accelerates the decay of uncapped walls. The future design of both stabilized and unstabilized external rammed earth walls must ensure effective protection from rainfall through well-proportioned overhanging eaves. While the capping of feature walls may be aesthetically pleasing, and thus architecturally desirable, it does not adequately protect the walling against long-term decay.