Technical Corner: Foundation Structures

At the current stage of construction, we focused on the foundation structures. The foundation footings were built using concrete blocks with a bottom. This system differs from common practice in the Czech Republic – there, blocks are typically used as permanent formwork, filled with concrete throughout. In Zambia, however, the blocks have a bottom and function more like "bowls," which are only filled with concrete. After laying the blocks, we poured the footings with concrete and allowed the structure to cure for several days.

The reinforced concrete slab follows on from the footings. The slab creates a height difference between the surrounding terrain and the perimeter masonry, protecting the mud brick walls from standing water and rain splash. The slab itself is 100 mm thick, which is a compromise between local habits (50 mm) and the requirement for long-term durability. Locally used thinner slabs tend to degrade down to the subgrade once cracks appear.

To limit the formation of cracks, we reinforced the slab with a conforce wire mesh. This local product is not identical to the standard welded mesh – the rolls consist of rods of varying diameters (1.8–4.5 mm) and have irregularly sized, mostly rectangular openings. To eliminate weak spots, we used multiple overlapping layers of the rolls.

This year, the formwork was made of planks. It turned out that the local workers handled them much more skillfully than formwork panels, which are hard to find on the market and also very expensive. During pouring concrete, we encountered a problem – the reinforcement tended to float to the surface. Thanks to the experience of our colleague Patrick, a local mason, we managed to fix the reinforcement in the correct position using nails driven into the foundation footings.

The final touch was the concrete mixing itself. While in the Czech Republic we would use a mixer, the locals prefer manual preparation directly on site. It is physically demanding, but it fits well into the local work culture.

Our aim throughout the process is to find a suitable middle ground – making use of traditional local methods while at the same time introducing more efficient techniques. Thus, the construction is not only about the end result but also serves as an educational platform for members of the local community, who gain valuable experience that will help them find employment on the labor market.

The resulting foundation slab is additionally divided into six sections with expansion joints. These joints are important because they allow the concrete to naturally expand and contract with changes in temperature and humidity, while also reducing the stresses caused by shrinkage during curing. As a result, the risk of uncontrolled cracking is minimized, and the slab retains its stability and load-bearing capacity in the long term.