The rammed earth technique may be one of the oldest known construction methods, but it is worth delving into updating it for modern times. As an environmentally friendly, strong and highly aesthetic material, rammed earth has as much potential for the future as it did in the past.
This natural material has been used in construction for thousands of years. Commonly used, the technique was applied in both ancient monuments and vernacular architecture, including the Great Wall of China. For its structure it uses local materials, so they have low levels of embodied carbon and produce little waste.
Building with Rammed Earth begins with constructing the frame for the walls. Usually composed of two parallel plywood panels, the frame is filled with a layer of moist soil, which usually includes sand, gravel, clay and a stabilizer. After this layer is added, it is compressed to approximately half its volume using a pneumatic tamper. This process is repeated repeatedly until the frame is filled with compacted soil, removing the wood and shaping a free-standing rammed earth wall.
Building with this environmentally friendly material requires an understanding of the climate and location where the structure will be built. Generally, the technique works best in climates with high humidity and relatively moderate temperatures. In colder climates, rammed earth walls may need additional insulation, inside or outside, while in high rainfall locations, they need additional protection from the rain. Additional measures can be taken to improve their performance. For example, to increase their thermal performance, additional insulation can be added to the walls. When considering possible water damage, the walls should be protected with overhanging eaves and be elevated on solid foundations at least 225 mm above ground level.
Sometimes, to increase the bearing capacity of the walls, cement is added to the original soil mix as a stabilizer. This mixture is known as Stabilized Rammed Earth (SRE). However, this addition decreases the sustainability promised by the technique, due to the high levels of embodied carbon in the cement.
As an organic architecture studio, we are always trying to find new ways to build in a more sustainable way and for us, this is definitely one of them. We are already in the process of building one of our projects in which the walls of the villas are completely made of rammed earth, so we are very excited to show the results to you.
Here are some of the advantages and disadvantages of building with this beautiful and natural material:
Advantages of rammed earth
- Unique appearance, the tone of the walls is determined by the soil and aggregate used. The tamping process is layer by layer, each one can obtain a different color and thickness.
- Material is easy to obtain locally, minimizing transportation and labor costs.
- The soil can be reused after a possible demolition.
- High structural capacity in both load-bearing and non-load-bearing walls, stabilized soil in monolithic walls responds to wind and seismic conditions.
- Fire safety, rammed earth is classified as a non-combustible material.
- With thermal insulation, rammed earth absorbs high temperatures achieving thermal comfort inside.
- Moisture resistance, rammed earth has great durability, but most rammed earth walls are porous by nature and need long-term rain protection.
- Sound insulation, Monolithic rammed earth walls provide effective acoustic separation.
Disadvantages of rammed earth
- Not all soils are suitable for this type of construction.
- In spite of being an old technique, there are not enough regulations to carry out this material work and this leads to greater construction controls.
- As it is a layered process with formwork, more work time is required.