Can you build a rammed earth wall in high humidity?

Understanding Rammed Earth in Humid Climates

Rammed earth construction has been used for centuries in arid and desert climates, where high temperatures and low humidity prevail. However, the same principles can be applied to high-humidity environments with modifications to the soil mix and construction techniques. To achieve a durable rammed earth wall in high humidity, it’s crucial to focus on water management and the selection of suitable materials.

Creating a Water-Resistant Soil Mix

In humid climates, the soil mix should be formulated to be more resistant to water absorption and less prone to erosion. A good starting point is to increase the proportion of sand and gravel in the mix, which will help improve drainage and reduce the risk of water accumulation. Aim for a mix with a minimum of 20% sand and 10% gravel, and incorporate additives like silica or cement to increase its water-resistance. A typical mix could be: 40% clay, 30% silt, 20% sand, and 10% gravel.

Designing for High Humidity

When building a rammed earth wall in high humidity, it’s essential to consider the wall’s design and layout. Use thicker walls (at least 200mm) to reduce the risk of water penetration and ensure better thermal mass. Also, incorporate a cavity wall design, where the rammed earth core is separated from the outer finish by a drainage gap. This will allow any moisture to escape, reducing the risk of water damage and mold growth. Consider using a breathable membrane, like a cement-based render or a lime-based finish, to protect the wall from external moisture while allowing the interior to breathe.