South Africa's building industry has taken another step forward. High up on a hill overlooking the sea in Noordhoek, Western Cape, stands the House that Hemp Built.
The first of its kind in South Africa, the building was constructed almost entirely of materials that could be grown on a few hectares of land within months.
The house belongs to Tony Budden, co-owner of hemp company Hemporium, who has been exploring and showcasing the product in South Africa since founding his company in 1996. He’s been working on his remarkable home since 2005 and his idea has finally become concrete - or rather, hempcrete.
The house was conceived as a prototype for future projects in South Africa. Housing is one of the government’s most pressing challenges, and building with hemp (Cannabis sativa) could make housing projects more affordable and more sustainable.
In four months one hectare of hemp can produce enough material for a strong and well insulated home that’s suitable for the government’s Reconstruction and Development Programme (RDP).
And after harvesting the first crop, materials for another house could be grown on the same land.
Ideal eco-building material
Hemp is increasingly being recognised as an ideal eco-building material, especially in Europe and Britain, where authorities are using hemp in pilot homes in their housing and eco-estates.
When Budden started the project, his major challenge was to find a local contractor who had experience in building with hemp. The solution presented itself when he was approached by green architect Erwin van der Weerd, who was pioneering a new modular building system for which he wanted to use hemp.
At his Stellenbosch factory, Van der Weerd constructed panels for the hemp house’s walls and transported them to Noordhoek, where it took a few days to assemble the house out of what looked like Lego blocks for grownups.
Modular building is much faster than the conventional process and could be effective in an RDP housing project, because all the work that requires technical expertise could be performed at a central location. Houses could be churned out at speed and would go a long way towards reducing the current housing backlog without affecting quality and safety.
Apart from its wooden frame, the House that Hemp Built is constructed mostly from the renewable plant. As far as possible, the panels’ inside posts are made of reclaimed wood. Inside the panels are two layers of hemp insulation and, in addition to this, the walls are strengthened with hempcrete. This is a mixture of lime, water and hemp stalks; a by-product of the textile industry.
Hempcrete continues to strengthen as it gets older and harder, and the spaces between the stalks create additional insulation. The walls are plastered with hemp screed which is similar in formula, but with more lime and some sand.
Some walls in the house are made from hemp chipboard, for which Budden negotiated with Chinese suppliers to develop a board that used an eco-binder instead of formaldehyde. These pioneer technologies are not cheap and, with the imported materials, the costs of the hemp house are comparable to a conventional building of the same size.
Article continues on page two: the contentious issue of hemp's illegality...