From the ground up: research on rammed earth and timber for a residential building

Abstract

Rammed earth is a building material that consists of compacted clay, sand, gravel and stones. It is a great option to consider for sustainable constructions, in combination with timber, since earth is abundant almost everywhere and the technique requires minimal energy. However, it is not used as a building material in Sweden today. This master thesis aims to spread knowledge of the material properties, architectural qualities, and practical applications for rammed earth and timber, show how rammed earth is being used in central Europe today, investigate how rammed earth and timber can be combined to construct a 4-story residential building and explore how the erosion of a weather-exposed rammed earth facade can be an integrated part of the design. The research method starts with examining the literature on rammed earth and timber. Erosion and pigmentation of rammed earth are then explored further with material tests. Observations from visits to rammed earth projects in central Europe and the company Erden’s prefabrication factory are then presented. The knowledge gained from these investigations is then implemented in the design of a 4 -storey residential building of rammed earth and timber. Timber is a lightweight material that can be used structurally in compression and tension, while rammed earth is heavy and can only be used in compression. These properties, among others, make timber and rammed earth a good combination, which is emphasised in the design. The design implementation shows that a residential building constructed with rammed earth will need a larger footprint than one constructed with timber only, due to the thicker walls. However, rammed earth offers great qualities such as unique appearance, deep window niches, acoustical and fire separation, recyclability, indoor moisture control and great air quality. But further developments in this technique need to be done for it to become an economically viable option in Sweden. By spreading the knowledge gained from this master thesis to the field, interest might eventually lead to investments in rammed earth construction.