Photographs: Tobias Helmersson, Clayworks, Hive Earth, Sirewall, Erika Alatalo
Shaping Rammed Earth Walls with Natural Clay Colors and Pigmentation explores how the composition of gravel, sand, silt, and clay influences both the structural and aesthetic qualities of rammed earth construction. This technique compresses gravel, sand, silt, and clay into stratified layers, with natural hues ranging from red and white to yellow and purple. A workshop in Karsi Kunda, Gambia, led by architect Erika Alatalo and artist Doedoe, found that natural clay variations often produced more cohesive aesthetics than artificial pigments. In 2021, Tobias Helmersson from Chalmers School of Architecture studied iron oxide and ochre pigments, observing how erosion alters pigmentation over time. Ghanaian firm Hive Earth, led by Joelle Eyeson, integrates natural and pigmented earth tones in West African architecture. Rammed earth also extends to interiors and furniture, as seen in Nando’s Chesterfield restaurant and the Hundertwasser Park Centre in New Zealand. Projects like Local Collective’s clay seating at the London Festival of Architecture showcase its broader applications. Combining traditional craftsmanship with modern techniques allows architects to push rammed earth’s potential in contemporary design.
Rammed earth, one of the oldest wall construction techniques, continues to offer significant potential for modern earth-based architecture. A key aspect of this potential lies in its natural colors and layered composition, which emerge once the formwork is removed, revealing a distinctive stratified character. This method, which involves the sequential compression of gravel, sand, silt, and clay, results in a horizontal arrangement of earth tones influenced by material composition and curing processes. The visual qualities of rammed earth walls can be intentionally shaped and refined through patterns, textures, pigmentation, and natural clay colors, expanding its architectural possibilities.
The color variations in rammed earth walls are determined by the diverse soil properties found across different locations. Soil type influences not only the mechanical characteristics of the compacted layers—where a direct correlation exists between dry density and compressive strength, with higher density resulting in greater strength—but also the visual appearance of the walls. Natural clay occurs in a range of colors, including red, white, yellow, and purple, making each rammed earth structure inherently tied to its local soil resources. This raises the question of how much pigmentation is necessary to introduce further variation within the layers.
A workshop led by Finnish architect Erika Alatalo, in collaboration with Gambian artist Doedoe, took place in the village of Karsi Kunda in eastern Gambia, focusing on the construction of rammed earth walls. At the time, this building technique was unfamiliar to the local community. The workshop aimed to examine the visual impact of the village’s natural clay colors and the effects of added pigments on the soil. Given the area’s diverse clay resources, one iteration involved compressing each layer using different natural clay colors, while another incorporated introduced pigments. The results varied, with red and black pigments producing intense colors, whereas yellow, blue, and white pigments blended into the mix and became less visible. Despite the bold contrast created by the red and black pigments, the architect observed that they did not integrate as seamlessly or aesthetically as the natural clay variations.
In 2021, Tobias Helmersson, a student at Chalmers School of Architecture in Sweden, investigated the effectiveness of pigmentation in rammed earth. His research involved testing red iron oxide, black iron oxide, and yellow ochre in varying quantities on small earth cubes. Notably, the yellow ochre produced minimal visual change, likely due to its similarity to the base soil color. His findings also revealed that erosion can create a color gradient on rammed earth facades. When high-pressure water was applied to a red rammed earth cube, the exposed pigment appeared less red than the uneroded surface, demonstrating that rammed earth color changes with increasing erosion depth.
The work of Joelle Eyeson and her Ghana-based rammed earth construction company, Hive Earth, demonstrates a refined approach to balancing natural clay colors and pigmentation. Committed to building accessible and environmentally sustainable housing in West Africa, Hive Earth utilizes locally sourced materials to challenge conventional perceptions of earthen construction. Their design process incorporates layered compositions with wave-like patterns and natural textures, blending earth tones while creating bold contrasts through pigmentation. Each wall is intentionally crafted, transforming the construction process into an artistic expression, with every cast within the formwork resulting in a unique outcome. Joelle Eyeson states, “Many of the colors you see on the walls are natural colors of the earth. In Ghana, we have a wide range of earth variations, allowing us to achieve light beige, gray, red, or even black hues. Sometimes, if requested by the client, we add iron oxide pigments to create brighter colors.”
Rammed earth wall finishes exhibit a distinct warmth, with each application highlighting the richness of different soils. The interior of Nando’s restaurant in Chesterfield demonstrates how pigmented clay can introduce vibrant colors and textured surfaces, enhancing the dining environment. Another notable example is the Hundertwasser Park Centre in Kawakawa, New Zealand, where layered colors reflect elements of the surrounding landscape, such as ocean inlets and clouds. Beyond architecture, rammed earth is also used in furniture and interior fixtures. Local Collective, for instance, created clay seating for the London Festival of Architecture and Network Rail, incorporating layers of locally sourced clay from London. This public installation allows visitors to engage with the tactile and visual qualities of the material.
Incorporating modern construction techniques into rammed earth walls provides a foundation for future innovations. Despite its limitations, the material’s malleability allows for diverse architectural applications. Exploring the balance between natural clay colors and pigmentation offers a pathway for integrating rammed earth into contemporary design. This approach underscores the importance of intentional artistic processes within standardized construction methods while challenging perceptions of local earth materials, particularly in the global south.
Gallery
