What Is Rammed Earth Wall Construction?
What Is Rammed Earth Wall Construction?
Rammed earth walls are a traditional building method that involves compacting a mixture of soil, gravel, sand and clay into formwork. The mixture is traditionally compacted by hand using a wooden pole, but modern technology uses a mechanical ram.
A variant of traditional rammed earth is stabilized rammed earth, which involves adding a small amount of cement (usually 5-10%) to increase the strength and durability of the walls.
Stabilized rammed earth walls often require little additional protection, but they are typically coated with an air-permeable sealer to prolong their lifespan.
Rammed earth walls are also known as “pisé walls,” a term that refers to the process of constructing walls at least 500mm thick by compressing earth between two parallel frames.
Modern rammed earth walls in Australia are typically built using cement as a stabilizer and are 300mm thick for external walls and 200-300mm thick for internal walls.
History Of Rammed Earth Walls
Rammed earth is an ancient building technique that has been used for thousands of years. It was widely used in China particularly in the construction of ancient monuments and traditional architecture such as the Great Wall. However, interest in rammed earth declined in the 20th century.
However, some modern architects and builders continue to promote its use due to its sustainability. This is because rammed earth structures are made from local materials which means they have a low embodied energy and produce very little waste.
How To Build A Rammed Earth Wall?
To construct rammed earth walls, a mold is necessary to define the shape of the wall. We use straight bamboo panels that provide smooth and straight walls. While not always necessary, some builders prefer to stabilize the mixture with cement.
Traditional stabilizers can include animal blood and limestone. Before compaction, the mold is filled with slightly moist soil to a depth of 8-15cm. To compact the soil, we use a stamper, which consists of a heavy foot (weighing between 3-8kg made of steel, wood, or stone) and a handle.
By repeatedly lifting and dropping the stamper, a compaction of up to 50% is achieved. Once the top of the mold is reached, it can be removed and placed on top of the created wall to continue building or set on the side to extend the wall horizontally.
In order to ensure a long-lasting wall, it is important to provide a water barrier towards the ground and a roof above the wall to keep the horizontal top of the wall dry.
Types Of Rammed Earth Walls
Rammed earth is a building material made from clay, sand, silt, and water. There are two types: raw, which just these natural materials is mixed together, and stabilized, which has a binder such as cement added.
Many architects prefer to use raw rammed earth because adding a binder alters the material’s properties and prevents it from being recycled back into the earth.
Durability And Moisture Resistance
Rammed earth is a durable building material that has been in use for thousands of years. It is still used today and there are many examples of rammed earth buildings that are centuries old.
To ensure the longevity of rammed earth buildings, it’s important to protect the tops and bottoms of walls from water damage.
Although rammed earth has moderate to good moisture resistance, additional waterproofing may be necessary in some cases. New additives that waterproof the walls may make rammed earth suitable for exposed conditions, but may also inhibit the breathability of the material.
Benefits Of Rammed Earth Wall
Rammed Earth Walls, made from a mix of dirt and soil, can be beautiful and come in a range of colors. They have thermal mass which is useful in places with large temperature swings and are popular in the south. Adobe walls are also cost-effective with most of the cost coming from labor.
They are an all-natural, healthy building material with no out-gassing of volatile organic compounds or red-listed ingredients.
Additionally, adobe walls have excellent acoustic properties keeping noise out and improving sound reverberation.