What is Process for Creating Curved Walls in Earthbag Design?

Designing the Curved Shape

When designing a curved wall in an earthbag structure, it’s essential to start with a clear plan. This can be achieved by using a string and stick method or by creating a scale model to visualize the shape. A dome shape, for example, requires a specific ratio of wall thickness to radius, typically around 1:10 to 1:15. It’s also crucial to consider the structural integrity of the wall, taking into account the stress concentrations that may occur at the curved sections.

Building the Curved Wall

To build a curved wall, earthbags are typically laid in a spiral pattern, starting from the center and working outward. This helps distribute the weight evenly and creates a stable structure. A key technique is to use a " spiral anchor" system, where a series of barbed wire wraps are tied to the earthbags at regular intervals to prevent them from shifting or collapsing. The spiral pattern can be either clockwise or counterclockwise, depending on the design requirements.

Finishing the Curved Wall

Once the earthbag structure is complete, it’s essential to apply a suitable finishing material to protect the bags from the elements and create a smooth surface. A natural plaster, such as a mixture of lime, sand, and water, is a popular choice for its durability and aesthetic appeal. The plaster is applied in multiple thin layers, allowing each layer to dry before applying the next. This process helps prevent cracking and ensures a strong bond between the plaster and the earthbags.