Innovative new approaches to local materiality are being explored and developed by local architects and built environment professionals in East Africa. The emphasis is on finding low carbon solutions to building construction, through promoting local materials and reducing the cement content in buildings. By shifting from carbon-intensive foreign material imports to local labour-intensive construction techniques, architects can leverage the construction process to develop skills and local expertise, while significantly reducing the embodied energy content of their buildings.
Adhesives can optimise the structural characteristics of wood and turn short lengths or timber and wood waste into composite panels or beams.
The use of adhesives can make timber much more useful and reduce wastage by diminishing the negative impact of knots and other small defects. Often the manufacture of these products requires considerable investment in technology, but some techniques can lend themselves to small scale production of high strength materials. The critical issues are making sure the timber is dry and very accurately machined, using the right moisture-resistant structural adhesive and ensuring the curing process is followed carefully. Engineered wood contains more embodied energy than solid timber but far less than reinforced concrete and steel.
At the Rubengera Technical School, Rwanda, they are experimenting with laminated timber as well as I-section timber beams.
Light Earth Structures
Thin, compressed stabilised earth tiles can be formed into parabolic vaults with the ability to span up to 16 meters.
South African architect Peter Rich along with Tim Hall, and engineer Michael Ramage have developed an innovative shell vaulting technology, which is a fusion of architectural design, advanced structural analysis and labour-intensive local material production. Hydraulically pressed stabilised earth tiles are laid into a temporary formwork where they are 'glued' together with a gypsum mortar. Several further layers incorporating plastic geo-textiles are applied to create a spectacular self-supporting shell structure. The technology requires careful supervision, but unskilled workers can be easily trained in the technique.
The Rwanda Cricket Pavilion consists of three self-supporting parabolic roofs made from compressed stabilised earth tiles
100% recyclable and biodegradable. Strawboard panels are a carbon negative alternative to cement-based load bearing walls
Strawtec panels are a newly available construction material manufactured in Rwanda. The strawboards are extremely robust and offer a high performance, fire-resistant and load bearing alternative to concrete or fired brick walls. The panels are made from agricultural waste, that would otherwise be burned for disposal, in a dry extrusion process that binds straw together using its own natural adhesives. The process produces zero toxic waste and requires very low energy input. Strawtec aims to stop East Africa's over-reliance on imported materials and instead offer an opportunity to export new construction materials to neighbouring markets.
Strawtec recycles agricultural waste into a high performance, carbon negative building product
Organic concrete uses vegetable substances instead of chemical and mineral additives used to produce concrete.
Biocrete is based on a mixture of natural fibre, residues from agricultural waste and hydrated lime. Rice husks and coconut coir can be supplemented for aggregate, while starch from cassava peel can be extracted and used as an additive to improve the processing properties of concrete. Cassava peel and rice husks can be burned as fuel to produce a pozzolanic ash, which reacts with lime and water to create a sustainable cement substitute. Biocrete is not a strong as concrete and is best used for infill walls and flooring rather than primary structure. However, strategic use of the material can drastically reduce the cement content of buildings.
Possible materials for East African Biocrete: rice husks, ash from cassava peels, karroo gum and coconut fibres
Building with recycled materials is an innovative and cost-effective construction solution that helps to keep the environment clean.
Waste products can often be reused, upcycled or recycled for use as construction materials. An example of this is the low-tech recycling and innovative application of plastic bottles. These can be filled with sand or stuffed will single use plastic until they reach a high enough density to make them into a solid building block. Plastic waste can also be woven into screens, shredded and compressed into tiles or combined with sand and aggregate to make pavers. Alternatively, whole plastic or glass bottles can be inserted into the wall or roof structure to allow light to penetrate into interior spaces.
The Ross Langdon Health Education Centre uses recycled plastic bottles to create 'litres of light'