Interlocking Stabilized Soil Blocks

Exhibition: Cities | October 11, 2011 by

In Uganda’s urban areas, where 53,000 homes are needed annually to maintain population growth, fired clay bricks are among the most common building materials. However, unmonitored clay extraction increases soil erosion and degradation. Trees are cut down to fire bricks, contributing to deforestation and air pollution and reducing fuel sources needed for other activities.Interlocking Stabilized Soil Blocks (ISSB), an affordable and environmentally sustainable alternative to fired bricks, are made from soil stabilized with 5% cement, compressed in manually operated machines, and dried in the sun. In the 1990s, Moses Kizza Musaazi of Technology for Tomorrow developed a double-interlocking system for the blocks, similar to a tongue-and-groove joint—when stacked, ridges on the top of one block fit into slots on the bottom of the next block, and side ridges fit into side slots of corresponding blocks. Musaazi introduced both straight and curved blocks, the latter used in the construction of water tanks, granaries, and biogas digesters. The blocks perform better than clay bricks by increasing the structural stability of built walls while reducing the amount of cement needed as mortar. ISSB are made onsite, reducing transportation, fuel, and construction costs. The building technology is easily transferable and culturally appropriate in urban areas where building with earth bricks is already common.

Designer: Moses Kizza Musaazi, Technology for Tomorrow. Manufacturer (block press): Makiga Engineering Services. Kampala City, Uganda, 1993–present. Soil, Portland cement


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