Do rammed earth structures require specific foundation types?

Foundation Types for Rammed Earth

Rammed earth structures can be built on various foundation types, but the ideal choice depends on local soil conditions, climate, and the design load. In areas with stable soil or rock, shallow foundations such as spread footings or isolated footings can be used. These foundations transfer loads directly to the ground, minimizing the risk of settling or shifting.

Design Considerations for Desert and Arid Climates

In desert and arid climates, it’s essential to consider the high thermal mass of rammed earth and the potential for soil settlement. To mitigate these issues, designers can use a combination of shallow foundations and a well-designed drainage system. A 6-inch (150 mm) thick concrete slab with a 4-inch (100 mm) layer of compacted aggregate can provide a stable base for the rammed earth walls. This design also allows for moisture movement and thermal expansion, reducing the risk of cracking and damage.

Formwork and Soil Mix for Successful Foundations

To ensure a strong and durable foundation, it’s crucial to design and build the formwork and soil mix correctly. For rammed earth walls, a mix of 1 part cement to 2.5 parts sand to 4 parts aggregate (by volume) is commonly used. The formwork should be designed to transfer loads to the foundation and provide a smooth surface for the soil mix. A 1-inch (25 mm) layer of compacted aggregate beneath the formwork can help with drainage and prevent waterlogging.