Quick Answer
Rammed earth can be used for landscaping features, such as retaining walls, planters, and decorative elements, as long as the mixture is formulated for exterior use and can withstand local climate conditions.
Choosing the Right Soil Mix
When using rammed earth for landscaping features, it’s essential to create a mixture that can withstand local climate conditions, particularly in desert and arid climates where erosion and extreme temperature fluctuations are common. A typical mixture for exterior rammed earth walls consists of 10% clay, 20% sand, and 70% aggregate, such as gravel or crushed stone. However, for landscaping features, you may need to adjust the ratio of aggregate to improve drainage and prevent waterlogging.
Formwork and Construction Techniques
To create rammed earth landscaping features, you’ll need to construct a form to hold the mixture in place. Use a sturdy frame made of wood or metal, with a minimum of 2x6 lumber for the sides and 3/4 inch plywood for the bottom. Compact the soil mixture in 2-3 inch thick layers, using a hand tamper or a mechanical compactor, and vibrate the form to remove air pockets. Apply a release agent to the form to prevent the rammed earth from sticking.
Thermal Mass and Climate Considerations
Rammed earth landscaping features can help regulate soil temperature and retain moisture in desert and arid climates. The thermal mass of the rammed earth can help absorb heat during the day and release it at night, reducing the need for irrigation and minimizing soil temperature fluctuations. To maximize thermal mass, use a mixture with a high clay content and apply a layer of plaster or stucco to protect the surface from erosion.
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