Stabilised Soil Blocks (SSB)

This technology is not new. It has been used since at least the 1950s in West Africa and is gaining in popularity now in East Africa.  Essentially, the hand-powered press uses soil, the traditional building material, to create a strong durable block to build with. Structural strength comes from the compression and adding a small amount of cement (usually around 5-8%) makes the block waterproof and so suitable for external walls. The blocks have a beautiful, earthy feel reflecting the local landscape.

Although hand-made, the press also ensures consistency of shape which is a problem with traditional bricks. The soil block also has excellent thermal properties and so helps keep buildings cool during hot weather.

As the block is not fired, there is a significant saving of around 1 MT of firewood (800kg carbon) per 1,000 blocks over local fired bricks. So where fired-brick is the standard building material, such as in Malawi, there is a significant environmental benefit. We are currently developing a methodology to measure this benefit.

An additional benefit comes from the inter-locking feature (ISSB). This allows dry stacking and so saves money because less mortar is required. But we have found when we use cement in the mix, there is no significant financial saving over hollow concrete blocks (common in the Zambian towns and cities).

As cost is critical, we are exploring ways of reducing the amount of cement needed. For example, not adding to blocks for internal walls.

In Zambia we have used the ISSB on most of our projects as we like the product and the people we have trained are able to set up their own supply business. Two people can make at least 300 blocks a day.

In rural areas, we believe that there is a market for the stabilised soil blocks. But in urban areas, there is a false perception that concrete is better than earth and this needs to be overcome. For those concerned with environmental issues, the SSB may be the building material of choice.

The curved block version of the press has been trialed for constructing water tanks, linings to pit-latrines and in our African ‘Cool House’.

For more information:

Makiga Engineering

Craterre

Good Earth Foundation