Outdoor earthen plasters

Construction of ecological buildings has one specific sub-segment - construction with natural materials. These are buildings made of timber, earth, stone, straw bales, reed, hemp, etc. The majority of these materials need protection against external effects. Architectural or structural elements (roofing overlaps etc.) provide passive protection. Outdoor plasters may be used as an active protection element. The practice to-date has mostly applied lime plasters with high demands for treatment during the first two to three months. An alternative choice were unstabilized earthen plasters with high demands for maintenance. The research intention, therefore, was to develop an outdoor plaster based on natural materials resistant to external weather effects. The desired solution was a plaster of unburnt earth with slightly modified properties, mainly in reaction to water. In the first phase of research, extensive literature search, dozens of potential stabilizing agents were shortlisted. The selection criteria were: water resistance plus low diffusion resistance of the resulting material, improved strength characteristics, a zero effect on colour and appearance etc. Many alternative agents were rejected. Positive results were reached with special types of polymer binders applied in small doses into earthen plasters. It must be emphasized that it is the plaster quality that plays a significant role here (the analysis would provide a topic for a separate article). The plaster is also suitable for repairs and reconstructions of historical earthen structures. These plasters are protected by a utility model. Outdoor earthen plasters were first introduced to the Czech market at the end of 2009