Can rammed earth walls be built in areas with frequent temperature swings?

Understanding Thermal Expansion

Rammed earth walls are highly sensitive to temperature fluctuations, which can cause the walls to expand and contract. This thermal movement can lead to cracks and structural issues if not properly addressed. To mitigate this, a mixture of 20-30% sand, 60-70% silt, and 5-10% clay is recommended, as this higher silt content provides better cohesion and flexibility. Additionally, incorporating a 5-10% portland cement to the mix can improve the wall’s durability and resist thermal stress.

Designing for Thermal Mass

In areas with frequent temperature swings, a rammed earth wall’s thermal mass plays a crucial role in regulating indoor temperatures. A wall thickness of 24-30 inches (600-750 mm) is recommended, with a minimum of 12 inches (300 mm) of earth material in the lower section of the wall to provide adequate thermal mass. The wall’s surface finish can also be designed to reduce heat gain or loss, such as with a white or light-colored finish coat to reflect solar radiation.

Formwork and Construction Techniques

Proper formwork and construction techniques are essential to building rammed earth walls that can withstand temperature fluctuations. Using a steel or wooden formwork with a 2-3 inch (50-75 mm) overlap between each section is recommended, to allow for thermal expansion and contraction. A tamping tool or a hand tamper can be used to compact the soil mixture, and a level and string line should be used to ensure the wall’s surface is level and plumb.