Natural Materials: Unearthing the Everlasting Potential of Adobe
Adobe is an organic building material made from earth. Adobe is Spanish for mudbrick and the material is effectively just this; a brick made of mud. This material consists entirely of natural elements and has a very simple makeup.
It is in fact one of the oldest construction materials ever used, with its first applications dating back to 5100 BC in the Andes. It was extremely popular in ancient times due to its easy fabrication and versatile properties. Many ancient structures really demonstrate this such as the Great Mosque of Djenné in Mali which has been standing for over 800 years.
This traditional construction material with ancient roots continues to be employed in various parts of the world for its good value simplicity, sustainability, and effectiveness. Composed primarily of natural ingredients, adobe has stood the test of time as a reliable building material.
The composition of adobe revolves around a few essential components: clay, sand, water, and sometimes an organic binder such as straw. Clay serves as the cohesive element, binding the mixture together, while sand enhances its structural stability and reduces shrinkage during drying.
Water is crucial for moulding the mixture and facilitating its adhesion, though excess water can lead to cracking. The addition of straw further reinforces the mixture, preventing cracks and enhancing its tensile strength.
The fabrication process of adobe is relatively straightforward and whilst there are some variations in the process it typically involves the following steps:
Local soil with a suitable clay-sand ratio is collected. The ideal composition can vary depending on the specific location and climate.
The collected soil is mixed with water to create a workable mud-like consistency. This mixture is known as “slip.”
Addition of Binders:
Organic binders like straw can be added at this stage to improve the overall strength and reduce cracking. The straw is chopped into short lengths and mixed into the slip.
The slip is poured into moulds or formed into bricks using wooden frames. These shapes can vary from traditional rectangular bricks to more intricate designs for specialised construction needs.
The moulded adobe blocks are left to dry in the sun. Careful drying is essential to prevent cracks and ensure uniform strength.
After the initial drying phase, the adobe blocks are turned periodically to ensure the material dries evenly, minimising any distortion.
Once fully cured, the adobe blocks are ready for construction. They are typically laid using adobe mortar, which is similar in composition to the adobe bricks themselves. The mortar serves to bond the blocks together and create a stable structure.
Whilst this is the fabrication process for adobe bricks, the material’s versatility expands its applications well beyond just bricks.
Cob: a form of adobe that involves mixing straw or other fibres with the clay-sand mixture to create a more malleable material. This mixture can be hand-sculpted to form walls, arches, and rounded structures, enabling architects to be creative and explore more natural design themes.
Rammed Earth: In rammed earth construction, the adobe mixture is compacted into formwork using mechanical tools or manual labour. This technique produces dense, sturdy walls that can vary in texture and appearance based on the type of soil used.
Plaster and Sculptural Adobe: Adobe can also be applied as plaster over existing structures or used to sculpt decorative and functional elements. Thin layers of adobe plaster can be layered onto walls, creating a smooth finish while maintaining the thermal benefits of the material.
Earthbags: Another innovative approach involves filling bags with the adobe mixture and stacking them to form walls. This technique is particularly useful for quick and cost-effective construction, suitable for both temporary and permanent structures.
Adobe Panels: In some cases, adobe mixtures can be poured into moulds to create precast panels. These panels can then be assembled to form walls or other architectural features.
The Sustainable Benefits
The building sector is reported to be consuming up to 40% of the world’s energy and subsequently producing up to 23% of the world’s greenhouse gas emissions. The importance of lowering these figures is paramount in mitigating irreversible environmental damage and achieving the 1.5℃ Paris Agreement target. Making the switch to more sustainable alternative materials is the single most effective way to reduce the overall environmental impact of the building sector.
Adobe and rammed earth possess exceptional thermal mass properties. Their high density allows them to absorb, store, and slowly release heat, naturally regulating indoor temperatures. This inherent ability reduces the need for mechanical heating or cooling systems, leading to energy savings and decreased carbon emissions. A study conducted on the potential energy savings of using adobe-constructed houses in Cyprus found that irrespective of weather conditions, adobe buildings required less artificial heating in winter and less cooling in summer.
Local and Low-Impact Sourcing:
One of the most significant sustainable aspects of these materials is their reliance on locally available resources. Earth-based materials are often harvested from the construction site itself or nearby locations, reducing transportation-related carbon footprints. This approach supports regional economies, minimises environmental disturbance and brings down sourcing costs.
Minimal Embodied Energy:
The manufacturing process for adobe and rammed earth involves minimal energy expenditure compared to energy-intensive materials like concrete or steel. A study ‘reported an embodied energy value between 0.033 and 0.17 MJ/kg of adobe bricks and an embodied carbon between 0.0017 and 0.0129 kg CO 2 eq/kg; these values are much lower than the ones displayed by traditional fired bricks having an embodied energy of 1.2-4.1 MJ/kg and an embodied carbon of about 0.24 kg CO 2 eq/kg.’ With minimal processing and reliance on manual labour, the embodied energy in these materials is considerably lower, making them appealing choices for sustainable construction.
The raw materials used in adobe and rammed earth—clay, sand, and gravel—are naturally occurring and have a low carbon footprint. Moreover, these materials can actively sequester carbon dioxide over their lifespan. As the earth absorbs CO2 during the curing process, structures made from adobe and rammed earth essentially lock away carbon within their walls.
Reduced Waste Generation:
The construction process of earth-based materials generates minimal waste since excess material can often be reused or returned to the earth. Unlike conventional construction, where large amounts of waste end up in landfills, the use of adobe and rammed earth promotes a more sustainable and responsible approach to building.
Longevity and Adaptability:
Adobe and rammed earth structures have stood the test of time, showcasing their durability and resilience. These materials adapt well to different climates and seismic conditions, requiring less maintenance and reducing the need for replacement, which further conserves resources.
Incorporating adobe, rammed earth, and similar earth-based materials into modern architectural designs offers an exciting opportunity to merge sustainability with aesthetics. Many architects and manufacturers are now taking advantage of this incredible potential, producing various earthen materials and structures with innovative new takes on what can be done with this ancient material.
Using adobe is also an attractive option for homeowners as many look to put sustainability at the forefront of their homes. Adobe not only offers a minimalist natural aesthetic but its high thermal mass promises to save energy and therefore money for homeowners in the long run.
As a testament to its rising popularity, the Belgian architect Jean Dethier wrote a book on earthen architecture named: The Art of Earth Architecture. The book pays homage to the extensive history of earthen materials and their applications and explores the many possibilities of using this material in modern architecture.
There is currently a huge range of earthen material manufacturers such as Rammed Earth Works, Earth Blocks UK, The Earthen Floors company and many more. Many of these manufacturers specialise in local sourcing which enhances the sustainability of their production. It is recommended to seek a local source of production when using earthen products to reduce transportation-associated energy expenses and emissions.
The above structure really demonstrates the aesthetic potential of earth materials. It is a pavilion at Bushey New Cemetery with rammed earth walls that was designed by Waugh Thistleton architects. Construction took as little as 46 days and only required 8 workers.
adobe’s composition of clay, sand, water, and potential binders, combined with its straightforward fabrication process, has positioned it as a remarkable and enduring building material. Its ecological friendliness, thermal properties, and versatility continue to make it a valuable choice for architects, builders, and homeowners seeking a connection to tradition and a commitment to sustainable construction. To discover other sustainable alternatives that can reduce the embodied carbon of your project and improve the energy savings of your building, have a look at the Firstplanit website.
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