For our housing project in Niger, we are using Compressed Earth Blocks (CEB), a material that has only recently started being used in Niamey, Niger's capital. The blocks are produced from mostly basic dry soil with a small amount of clay and aggregate with typically 7-10% of cement added. Laterite soil is particularly good for producing them and Niger has this material in abundance. CEBs are load-bearing for a one to two story buildings and have been adopted in recent years by architects such as Francis Kéré, who uses them almost exclusively in his projects in Africa.
CEBs have many advantages, particularly over cement blocks.
- They are more sustainable because they use less cement. Cement production is one of the biggest causes of air pollution in places like China and the US, and the minerals have to be mined. In addition, cement production requires enormous amounts of energy.
- They perform remarkably well in the 100+ degree heat of Niger, producing cool interiors.
- They are fire, sound, and insect (huge advantage in Niger) resistant.
- They have a cultural resonance but as a higher quality, more modern and performant version of the traditional Adobe hand-molded blocks that have been used in Niger for centuries.
- They can be significantly cheaper than cement blocks, especially when made using manual presses with soil that can be procured nearby or on site.
However, using the material also has some drawbacks in our context. For one, the CEBs need to be protected from water either by plastering the walls or having a roof with enough overhang. Therefore, the foundation and the walls have to be carefully designed and executed to make sure water doesn’t touch the bricks from underneath. Furthermore, availability and production rates were a concern to us. The material is not widely used, and finding high quality bricks in ample supply almost made us consider purchasing our own press. Fortunately, we were able to find the right provider, but this remains an issue in general with using CEBs in large scale projects.
The biggest challenge has been that, in an urban setting such as Niamey, there is a stigma associated with building with earth that leads people to prefer cement blocks when they can afford them. Earth is unfortunately often viewed as the “poor man’s” material, and a sign of economic inferiority and cultural backwardness. This meant that we had to carefully consider whether we should expose the brick in all its beauty or not. We found the solution by inspiring ourselves from the local practices in Niamey in terms of finishing. Cement block houses are typically plastered with a thick cement coating, followed by a sand and cement plaster finish that yields a lovely earth tone. In reality, it conceals the cement, and mimics the traditional mud plaster used in adobe dwellings for centuries.
These precedents, coupled with the fact that exposed brick of any material is not typically done in the country, led us to settle on the sand plaster for our project facades as well. It really helped the buildings “belong” and blend in with their surrounding neighbors, while having a fairly distinctive design.