Should I Use Stabilized vs Unstabilized Soil in Earthbags?

Earthbag Soil Selection

When it comes to building with earthbags, the type of soil used can greatly impact the structure’s durability and performance. Stabilized soil, typically achieved through the addition of cement, lime, or Portland cement, provides better cohesion and resistance to weathering. This is especially important for dome-shaped structures, which are more prone to cracking and erosion. In contrast, unstabilized soil can be used for temporary or low-stress structures, such as animal enclosures or garden paths. However, unstabilized soil may not perform well in areas with high rainfall or freezing temperatures.

Soil Testing and Mixing

To determine if your soil is suitable for earthbag construction, test its compressive strength, cohesion, and plasticity. You can do this by performing a simple triaxial compression test or by consulting with a geotechnical engineer. If your soil doesn’t meet the required standards, you may need to stabilize it through the addition of cement or other additives. When mixing stabilized soil, aim for a 1:1 or 1:2 ratio of soil to additive, depending on the manufacturer’s recommendations. Mix the soil thoroughly to ensure uniform distribution of the additive.

Bagging and Construction Techniques

Regardless of whether you’re using stabilized or unstabilized soil, it’s essential to follow proper earthbag construction techniques to ensure a strong and durable structure. Start by filling polypropylene bags with the mixed soil, then use barbed wire to tie them together in a secure pattern. For dome-shaped structures, use a spiral pattern, while straight walls can be constructed using a simple overlapping pattern. Apply a layer of plaster or render to protect the earthbags from the elements and enhance the structure’s appearance.