Alternative building blocks from alien trees

Bricks made from alien trees, vaulted floors and ceilings … innovative design for Cape housing project addresses environmental issues and climate change, using old-school technology to reduce the fossil fuel footprint of construction.

An innovative collaboration between the Cape Town-based company nonCrete, the Institute of Technology in Architecture at ETH Zurich, Switzerland, and the South Africa’s Council for Scientific and Industrial Research (CSIR) has created a potentially game-changing design and construction methodology for housing alternatives.

The methodology is being implemented in a three-year project co-funded by the WWF Nedbank Green Trust and the CSIR’s Circular Economy Demonstration Fund. “Alien biomass to housing” started in April 2024 in partnership with nonCrete, the non-profit organisation Phuhlisani, and the Elandskloof community near Citrusdal in the Western Cape.

The Elandskloof community is on a farm that has been restored to approximately 500 inhabitants under the land reform process. They were dispossessed of their land in 1962 by the apartheid government, and it was returned to them in 1996. Nearly 30 years later, the residents are still living in informal dwellings.

Pilot project

The project is a potential life-changer for the Elandsklowers, and they are engaged in every stage, starting with a pilot 8m x 8m crèche to demonstrate the non-Crete method.

Stephen Lamb from nonCrete explains, “The bricks are the size of conventional bricks, but are made from the biomass of local alien invasive trees that are felled from the riverbanks, put through a chipper, and combined with a specially developed binder to create a low-carbon material”.

Elandskloof is situated in the valley of the Groot Winterhoek Strategic Water Source Area. It supplies water to Atlantis, Ceres and Saldanha and is one of 22 key water sources in South Africa. Its riverbanks are full of black wattle, and removing alien invasive trees within a 50 km radius will greatly impact freeing up available fresh water.

Using the alien invasive biomass, the nonCrete method significantly reduces the amount of stone, sand and cement used in standard concrete bricks. The bricks also have a higher degree of fire resistance and thermal qualities, helping to keep homes warm in winter and cool in summer.

In addition to the bricks, nonCrete has developed a vaulted floor and roof system in collaboration with the CSIR and the head of the Institute of Technology in Architecture at ETH Zurich, Prof Philippe Block.

Strength through geometry

“This exceptional design follows the motto of ‘strength through geometry. It is inspired by the arches constructed by master builders in the Gothic cathedrals of Europe that are still standing 500 years later and which we are using in European design”, Block explains.

“The floor and roof system significantly reduces the amount of steel and concrete required and has 75% lower carbon emissions than a conventional concrete flat slab. It complies with Eurocode load requirements for multilevel construction in residential, office and other buildings”, he says.

Once the demonstration crèche has been constructed, the Elandskloof Communal Property Association members can decide whether to use the method to build their homes.

“We are currently helping facilitate negotiations with the municipality and the provincial and national departments for the application of the housing subsidies to pursue the larger housing project”, says Phuhlisani’s David Mayson.

The plan involves on-site training of community members in alien invasive tree clearing and wood chipping, brickmaking and construction, which would create self-employment opportunities for community members.

 “We’re excited to see how catalytic this low-emission building system can be as it has vast potential and is increasingly gaining ground in research and construction locally and internationally”, says Poovi Pillay, Executive Head of Corporate Social Investment at Nedbank.

“The methodology has the potential to be duplicated across the country, starting in Elandskloof, and replace conventional, carbon-heavy building materials and practices. What is so effective is that carbon absorbed by the trees is locked into the buildings”, says Pillay.

“Our goal is to share this technology and acquired knowledge with South Africa and, where requested, to train people to build their own houses in all areas with an abundant supply of alien invasive tree species, which applies to many parts of the country,” says Lamb of nonCrete.

“We have been collaborating with One-Nil Construction, led by Grabeth Nduna, the CSIR and WWF SA. Nduna and nonCrete’s Peter Mafuwe and Mojalefa Thelingoana, have been pivotal in creating the material mix designs we require”, explains Lamb.

“NonCrete’s methodology aligns with the urgent need worldwide to change how we design and build our structures and disrupt the concrete, steel and carbon-intensive construction technologies for architecture. The exciting part is that with this Elandskloof project, we are taking a great idea and making it happen”, remarks Block.

Original article by Heather Dugmore, edited by Chris Chapman