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Rammed earth

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Rammed earth, also known as pisé, is an ancient construction technique used to create foundations, floors, and walls. It involves compacting natural raw materials into a solid mass. These materials typically include earth, chalk, lime, or gravel. This method is highly valued today as a sustainable building practice. It is often used because it relies on local materials. This reduces the energy needed for transportation.

Tapialdebarro
Tapialdebarro

The construction process begins with a temporary frame called formwork. This mold determines the shape and dimensions of the wall. Builders usually make formwork from wood, plywood, or steel. The frame must be very strong and well-braced. This prevents the walls from bulging under heavy pressure. Historically, builders used wooden planks tied with rope. Modern builders prefer more durable materials like steel.

Slipform
Slipform

To build the wall, workers use a damp mixture of subsoil. This mix contains specific proportions of sand, gravel, clay, and silt. Sometimes, stabilizers are added to make the mixture stronger. Historically, people used lime or even animal blood as stabilizers. The soil is poured into the formwork in layers. Each layer is then compacted until it reaches about 50% of its original volume. In the past, workers used long manual ramming poles. Today, many construction sites use pneumatic tampers powered by air.

Wall Finish
Wall Finish

Once the soil is compacted, the wall begins to cure. This means it becomes harder and stronger over time. If the surface needs carving or brushing, the formwork must be removed quickly. The walls become too hard to work with after about one hour. For cement-stabilized rammed earth, the curing process takes at least 28 days. The final strength of the wall depends on many factors. These include the soil type, moisture content, and the amount of stabilizer used.

Rammed earth wall surface
Rammed earth wall surface

Rammed earth has a very long history of use. Archaeological evidence shows its use in the Fertile Crescent during the Neolithic period. In China, the Yangshao and Longshan cultures used it around 5000 BCE. By 2000 BCE, the technique, known as hangtu, was common for Chinese walls. In the 1800s, the book Rural Economy helped popularize the method in the United States.

JiayuguanWall
JiayuguanWall

Notable American examples include the Borough House Plantation in South Carolina. In Canada, the St. Thomas Anglican Church was built this way between 1838 and 1841.

Borough House Plantation (Stateburg, South Carolina)
Borough House Plantation (Stateburg, South Carolina)

This building method offers many practical benefits. One major advantage is high thermal mass. Like concrete, rammed earth absorbs heat during the day. It then releases that heat slowly at night. This helps regulate indoor temperatures and can reduce the need for air conditioning. The walls also help regulate humidity. They can keep indoor humidity levels between 40% and 60%. Additionally, these walls are fireproof, non-toxic, and resistant to termites.

rammed earth
rammed earth

Modern engineering has found new ways to use this material. In Australia, cement-stabilized rammed earth (CSRE) is very popular. It uses a mix of low-clay soil, water, and cement. This version is much stronger than traditional rammed earth. It can withstand compression forces up to 40 megapascals. This makes it as durable as concrete. In North America, the Nk'Mip Desert Cultural Centre features a very long rammed-earth wall. As of 2014, it was the longest wall of its kind on the continent.

Nk'Mip DCC 1
Nk'Mip DCC 1
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File:Summer Vacation 2007, 263, Watchtower In The Morning Light, Dunhuang, Gansu Province.jpg
Summer Vacation 2007, 263, Watchtower In...
File:Tapialdebarro.jpg
Tapialdebarro.jpg
File:HouseBuildingInNorthernVietnam.jpg
HouseBuildingInNorthernVietnam.jpg
File:MurPise2.JPG
MurPise2.JPG
File:Slipform.jpg
Slipform.jpg
File:Rammed earth wall surface.jpg
Rammed earth wall surface.jpg
File:Wall Finish.jpg
Wall Finish.jpg
File:Oxide Finish Wall.jpg
Oxide Finish Wall.jpg
File:rammed earth.jpg
rammed earth.jpg
File:JiayuguanWall.jpg
JiayuguanWall.jpg
File:Grange.Bassey.Saint.Nicolas.Macherin.jpg
Grange.Bassey.Saint.Nicolas.Macherin.jpg
File:Borough House Plantation (Stateburg, South Carolina).jpg
Borough House Plantation (Stateburg,...

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