Which soil is used to make bricks

Uganda is currently one of the fastest-growing economies and most rapidly urbanizing nations in Africa, with an urban population growth rate of 5.3%. The urban population reached 15 million in 2025 and is projected to surge to 30 million within two decades; this rapid growth has resulted in a severe housing shortage. The country currently faces a deficit of over 2 million housing units, a situation President Museveni has identified as both a challenge and a significant market opportunity.

Uganda possesses abundant soil resources—which soil is used to make bricks—a topic we will explore in detail below.

Currently, traditional fired bricks remain the primary building material for housing in Uganda; however, this mainstream material is causing severe damage to the local ecosystem. Vast amounts of vegetation and trees are being felled, and the firing process releases significant quantities of exhaust gases—including carbon dioxide—resulting in serious local air pollution.

To address this issue, the Ugandan government actively introduced eco-friendly soil brick technology, procuring 50 to 60 soil brick-making machines and transporting them to the country’s northern region, where 30 housing units were built for local residents and the nomadic communities of Karamoja. The successful promotion of this technology in Uganda is fundamentally due to the country’s abundant and widely distributed clay resources; these are most concentrated around the capital, Kampala, where there are more than 50 clay extraction sites alone.

First, we analyze the central region of Uganda, where soil resources are most concentrated.

The region possesses abundant soil resources occurring in isolated basins. While historically used for the manufacture of tiles and pottery, the soil is now widely utilized for producing soil bricks; extraction is concentrated in the area, with over 570 active sites. The soil is composed primarily of kaolinite and quartz, with minor amounts of montmorillonite and feldspar. Chemically, it is characterized by a high silt content and elevated iron oxide levels, which give the soil its distinctive red or orange hue.

With a chemical weathering index of 98, the region has undergone intense chemical weathering. Local gneiss and granite have been weathered and eroded, and the resulting materials were transported by river water to be deposited around rivers and lakes, forming soil deposits ranging from 2 to 5 meters in thickness.

The red soil in this region is highly plastic and chemically stable, making it an ideal raw material for producing clay bricks. Furthermore, this soil is abundant and easily accessible across central Uganda; historically, it has been widely used to manufacture items such as pottery and roof tiles. While the local soil is excellent for brick production, we recommend conducting proportion tests involving soil, sand, and cement to determine the optimal mix for manufacturing the bricks.

There are numerous successful examples of soil brick projects in the region. Notable cases include the Kiryandongo post-disaster resettlement housing project, the Ongutoi Health Centre, Jesuit school projects, community polytechnics, chief’s housing projects, and the Kabarole youth project. These successes span diverse sectors—including post-disaster reconstruction, healthcare, education, and public infrastructure—demonstrating that soil brick technology is well-established and widely applied in the area.

Next is an analysis of the soil resources and their distribution in the eastern region of Uganda

The soil in this region differs significantly from the red soils found in the central region; its formation is linked to the volcanic activity of Mount Elgon, with soil deposits distributed primarily across the volcano and its surrounding areas, including Budadiri and Chelele. The soil is characterized by a predominance of montmorillonite-group minerals and a chemical composition rich in iron, aluminum, and silicon; notably, it exhibits high acidity, a factor that requires particular attention.

The soil found in eastern Uganda contains over 20% soil-sized particles and is characterized by high activity, strong cation exchange capacity, and high plasticity; while these properties make it excellent for ceramics, they present challenges for the production of soil bricks. To address this, we can optimize the material based on the soil’s specific characteristics. We can determine the composition ratio through a jar sedimentation test or by sending samples to a laboratory for professional analysis. Once the detailed soil composition is known, we can blend in the appropriate amount of sand and adjust the lime and cement dosages, using iterative testing to establish the optimal raw material mix.

There is a positive correlation between the amount of cement used and the strength of soil bricks; generally, higher cement content results in greater strength. The recommended cement content is 7%–10%. Cement undergoes a hydration reaction with water, producing a gel that binds soil particles tightly together to form high-strength bricks. Consequently, increasing the cement content in the raw materials generates more of this binding gel, thereby enhancing the brick’s strength; conversely, insufficient cement leads to loose, weak bricks.

However, excessive cement usage drives up production costs. Therefore, it is necessary to strike a balance between strength and cost. To this end, our engineers have conducted extensive experiments and compiled the following table illustrating the relationship between cement content and strength.

Next is an analysis of the soil resources and their distribution in the western region of Uganda

The soil resources in western Uganda can be categorized into two main types: kaolin found in the southwest, and illitic soil located in the southwestern highlands and the Rift Valley zone. The kaolin—which contains iron oxides and features kaolinite as its primary mineral—represents a clay resource of industrial value in the region. The illitic soil is characterized by an illite content of 40%–50% and a plasticity index of 33%.

The high-plasticity soil is formed through the long-term weathering of granite; it possesses moderate plasticity and stable chemical properties, making it suitable for molding soil bricks. Beyond brick production, this soil is also valuable for manufacturing pottery and refractory materials, offering significant economic potential. In contrast, illitic soil exhibits high plasticity and is prone to cracking during drying if used directly for brickmaking; therefore, it requires modification—most simply and directly by adding sand—to adjust the particle size distribution and lower the plasticity index. Research by local laboratories indicates that a mixture of 50% illitic soil and 50% weathered bedrock can yield soil bricks with a strength of 4.5 MPa. The local government has previously donated dozens of brick-making machines to youth projects in the Kabarole district, demonstrating the region’s established expertise in clay brick production.

Finally, there is an analysis of the clay resources and their distribution in the northern region of Uganda

Influenced by local rivers and lakes, the soil deposits in northern Uganda are characterized by diverse types—predominantly sedimentary in origin—and a distribution pattern featuring small, concentrated pockets scattered across a wide area. According to assessments by the United Nations Development Programme (UNDP), the region possesses abundant soil resources and extensive deposits of non-wetland red soil, an ideal raw material for producing soil bricks. Furthermore, the region suffers from underdeveloped infrastructure and limited prior exploitation, presenting significant market potential.

Local authorities have already introduced soil brick technology and implemented the Nadunget housing project, constructing over 20 homes for the local community and thereby demonstrating the suitability of the region’s soil. The bricks used in the project were produced entirely from local soil; workers excavated the soil, crushed it into fine particles, and mixed it thoroughly with small amounts of cement and water. Using HR2-10 brick-making machines, the raw soil was pressed into bricks. Local construction workers successfully used these materials to build the houses, creating aesthetically pleasing structures with exterior walls that required no plastering.

Soil brick technology reduces housing construction costs across materials, labor, and transportation; compared to houses built with concrete blocks, those constructed with soil bricks offer a 40% cost saving, while also being eco-friendly and allowing for rapid construction. The cost savings stem from several factors: first, raw material costs are minimized as the bricks are primarily made from local soil, eliminating the need for purchasing and transporting materials. Second, production costs are lower; the bricks are formed using hydraulic pressure rather than firing, thereby conserving timber and coal resources. Third, construction costs are reduced; the bricks feature a unique interlocking design that simplifies and accelerates the building process while requiring minimal mortar.

Feedback from local builders indicates that a wall requiring seven days to complete with traditional fired bricks takes only two days with soil bricks. Over 70 housing units in Kiryandongo were completed within a year, a project that also provided local construction workers with training in soil brick technology.

Future Development Trends of Soil Brick Technology in Uganda

The development of soil brick technology in Uganda is poised to evolve from isolated projects to widespread adoption and from individual initiatives to a full-fledged industry. This progression—moving from government-backed pilot projects toward localized, large-scale operations—aims to establish a local supply chain for eco-friendly building materials, thereby addressing the dual challenges of housing shortages and environmental degradation. The Uganda National Bureau of Standards (UNBS) has formulated the US 849 standard, establishing clear specifications for the quality control of soil bricks.

Local Ugandan companies, such as Jericho Civil Engineering, are actively introducing and promoting soil brick technology. Furthermore, the Ugandan government has planned a program to provide free technical training in soil brick production to 10,000 young workers across the country; ultimately, this technology has the potential to create jobs for 30% of Uganda’s unemployed youth.

The advantages of soil bricks extend beyond mere raw material cost savings; they also offer benefits regarding labor, construction efficiency, and transportation. Market research in countries such as Uganda and Nigeria indicates that a soil brick costs only 30% of a concrete brick. Furthermore, soil bricks offer significant logistical advantages: Compressed earth block machine can be moved directly to the construction site, allowing for on-site production, curing, and usage. This approach not only reduces transportation costs but also eliminates the risk of breakage associated with long-distance transport.

High construction efficiency is another key advantage of soil bricks. Their interlocking design can increase construction speed sixfold, and the process does not rely on the expertise of master craftsmen; workers can fully master the construction method after only brief training.

Houses constructed using soil bricks also exhibit notable seismic resilience. This differs from the seismic performance logic of traditional building materials, which rely on mortar to bond components into a monolithic structure—a method prone to brittle shear failure. In contrast, clay brick structures utilize a dry-stacking construction method; their interlocking design allows seismic energy to be dissipated through friction.

To verify the seismic performance of soil brick houses, the World Architecture Association published “Full-Scale Test Conclusions” in 2022 following seismic simulations, determining that such houses could readily withstand low-to-moderate earthquakes. In 2025, the Association introduced a steel-strap frame confinement system for soil brick walls, boosting seismic resistance by an additional 18%–20% and enabling the structures to easily withstand earthquakes of moderate intensity. The feasibility of this approach was demonstrated in a Jesuit school project in Uganda, where the soil brick walls incorporated this steel-strap frame confinement system.

This concludes our overview of the soil distribution and characteristics in Uganda, as well as the properties of soil bricks. If you have any questions regarding the raw soil materials, production methods, curing processes, or construction techniques for soil bricks, please feel free to email us; our engineers will respond within four hours.

FAQ

01. Why did the Ugandan government choose to introduce soil brick technology?

The Ugandan government opted to introduce soil brick technology based on factors such as production costs, environmental protection, and ease of construction. First, the low production costs and rapid construction speed associated with soil bricks offer significant advantages in helping the government address the country’s housing shortage—a gap of over two million units. Second, soil bricks offer environmental sustainability; traditional brick firing had led to widespread deforestation and air pollution from burning wood, whereas soil bricks are produced via compression molding and require no firing, thereby helping the government tackle environmental issues. Third, the technology creates employment opportunities for Uganda’s young workforce; for instance, in the Kiryandongo project, the value-added rate of soil brick technology reached 50%, with a substantial portion of expenditures translating into workers’ wages and providing jobs for unemployed youth.

02. What are some classic, successful project examples of soil brick housing in Uganda?

First is the Nadunget housing project in northern Uganda. Launched in 2010, this project involved the construction of 20 three-bedroom homes through a collaboration between the local Karimojong people and the national defense forces; the project’s success facilitated the rapid spread of soil brick construction technology across the region. Next is the Kiryandongo resettlement housing project in central Uganda. Following a landslide in the Bududa district in 2010 that displaced a large number of people, the local government constructed 60 low-cost housing units within 11 months to provide shelter for the displaced population. Finally, there is the Ongutoi Health Centre in eastern Uganda. Funded by the charitable organization High Adventure Gospel Communications Ministries, this project entailed the construction of a health center complex comprising more than 20 buildings.

03. What is the plasticity index (PI) of soil, and why is it important?

The plasticity index (PI) of soil measures the variation in water content while the material is in a plastic state. The typical range for soil’s plasticity index is 5%–15%; values ​​outside this range can affect the strength of the resulting soil bricks. A low plasticity index indicates a scarcity of fine particles and insufficient cohesiveness, which can result in bricks with a loose structure and low strength; in such cases, adding more soil can enhance cohesiveness. A high plasticity index indicates an excess of fine particles, making the soil prone to swelling upon water absorption; this can lead to severe shrinkage and cracking during the drying and curing process. To mitigate this, the plasticity can be reduced by increasing the cement content or adding sand.

04. How fire-resistant are houses built with soil bricks?

Soil bricks are manufactured by hydraulically pressing a mixture of soil and a small amount of cement. The materials used are non-combustible and free of toxic substances, offering excellent fire resistance—one of the key advantages of soil bricks. Our tests indicate that walls constructed using standard soil bricks can achieve a fire resistance rating of four hours.

05. Why is sub-surface soil selected for the production of soil bricks?

When preparing raw materials for soil bricks, subsurface soil from a depth of less than 0.5 meters should be selected. Surface soil contains organic matter—such as humus, microorganisms, and plant roots—that interferes with the hydration reaction of cement when mixed, resulting in loose bricks with poor strength. Subsurface soil, however, has a low organic matter content and stable chemical properties, making it more suitable for brick production.

06. What impact has the introduction of soil brick technology had on the local building materials market in Uganda?

The introduction of soil brick technology has had a structural impact on Uganda’s local construction materials market. While the market was valued at over US$5 billion in 2025, domestic self-sufficiency stood at less than 50%, necessitating significant imports. Soil bricks are produced using local soil and a small amount of cement, eliminating the need for large-scale raw material imports or the consumption of vast quantities of wood and coal for firing. Furthermore, as they can be manufactured directly on-site and used for construction immediately after curing, this technology has been transformative for the local market; indeed, soil bricks have become a hallmark of Uganda’s green building movement.

07. What factors primarily determine the service life of soil bricks?

The service life of soil bricks is primarily determined by two factors: manufacturing quality and protective measures. Manufacturing quality encompasses a scientific raw material mix, standardized production processes, and proper post-production curing. The most critical protective measure is waterproofing the wall; this significantly enhances the bricks’ resistance to water penetration and extends their service life to over 20 years.