How can you build moisture-resistant rammed earth for green buildings?

1 What is rammed earth?

Rammed earth is a technique of building walls by compacting layers of moist soil in wooden or metal forms. The soil mixture usually contains sand, gravel, clay, and a small amount of cement or lime as a stabilizer. Rammed earth walls can have different colors and textures, depending on the soil type and the compaction method. Rammed earth is an ancient and low-cost method of construction that has many environmental benefits, such as low embodied energy, high thermal mass, and recyclability.

2 Why is moisture a problem for rammed earth?

Moisture is one of the main factors that can affect the durability and quality of rammed earth walls. Moisture can cause erosion, cracking, swelling, shrinking, mold growth, and salt efflorescence on the surface of the walls. Moisture can come from different sources, such as rain, groundwater, humidity, condensation, and plumbing leaks. Therefore, it is important to protect rammed earth walls from moisture exposure, especially in wet or humid climates.

3 How can you design rammed earth walls to resist moisture?

Designing rammed earth walls properly is one of the best ways to prevent moisture damage. It is recommended to use a soil mix with 60-75% sand, 10-20% gravel, 10-20% clay, and 5-10% cement or lime for adequate drainage and low clay content. Furthermore, concrete or stone foundations should be raised above the ground level and have a damp-proof course, as well as drains and gutters to divert rainwater away from the walls. Additionally, waterproof membranes or coatings should be applied to the base and top of the walls. To protect the walls from direct rain and sun exposure, roof overhangs, eaves, awnings, or verandas should be used. Lastly, windows, doors, pipes, or electrical outlets should be avoided near the bottom or top of the walls to prevent gaps or cracks that allow moisture entry; any openings or joints should be sealed with flexible caulking or flashing.

5 How can you maintain rammed earth walls to resist moisture?

To ensure the moisture resistance of rammed earth walls, regular maintenance and repair of any damage is essential. You should inspect the walls for any signs of moisture problems, such as cracks, erosion, discoloration, mold, or efflorescence. If you find any, you should identify the source of the moisture and fix it immediately. To keep the walls clean, use a soft brush or a damp cloth to remove any dirt or debris. Avoid using harsh chemicals or pressure washers that can damage the walls. Repainting or reapplying waterproofing or anti-fungal treatments every few years can help preserve the protection and appearance of the walls. Additionally, you should fill any cracks or holes with a compatible soil mix or mortar and smooth the surface with a trowel or a roller to match the color and texture of the wall.