Why Samhitakasha is the greenest accommodation in Cape Town

Samhitakasha is built from mud and straw, like many traditional African houses, but in this case using “cob” techniques perfected in parts of the west of Britain. It was built on a brown-field site, i.e. one that had a previous house on it, in an existing suburb (the previous house was demolished in the 1970s), rather than a green-field site – virgin soil which could be used for conservation or agriculture. As such, it was the first visible ‘organic’ house in a city suburb in the country – other ‘organic’ houses have been hidden away out of town or on smallholdings. During the building process the public (including many schoolchildren) were invited to open days to learn more about cob building, and although the original house plan is now complete there are still open days held from time to time.

Mud buildings were, of course, traditionally part of both colonial and African building techniques throughout South Africa (many of the country’s oldest buildings are made of mud, and some new ones in traditional villages are still made of mud). The mix of soil materials we used cost little to dig out of the ground, in contrast to fired bricks – a major source of greenhouse gas in their production – or concrete, which is an unrecyclable mix of chemicals. The walls are healthy and completely recyclable (unwanted sections can just be chipped off, moistened and reused), and are strengthened by straw, another natural material. The walls also breathe in a way fired brick and cement walls cannot: they allow moisture to flow in and out again (so no trapped damp), and they stay naturally cooler in summer and warmer in winter than the outside temperatures, cutting down on heating and cooling costs. The walls are plastered without using cement, just natural lime is used as a waterproofing substance outside, while inside the house environmentally friendly sealants and paints have been used on walls and floors. Where tiling has been needed we have used natural slate tiles.

The foundations of the house were made using compacted gravel – i.e. natural stone. Much of the structural support for the house is wood and there are many handcrafted window and door frames. The upright forest of poles supporting the first floor and roof were alien gum trees that were being cleared off a property, to reduce water use (in line with government environmental policy). Much of the structural timber is local pine, and the joinery is made for the most part from siligna, the only South African-grown sustainable hardwood. These wood items have all been protected with organic treatments and natural sealants. Other pieces, including lintels and most of the furniture in the guest room, have been made from reclaimed wood or old railway sleepers.

The roof, which is an unusual curving design, is made from insulating combinations of wood, recycled cardboard, clay and straw, with a final layer of torch-on bitumen as a waterproof element. The structural design is strong enough that in years to come we hope to add a ‘living roof’ of plants to act as an urban carbon sink.

Energy and water savings and green energy are also key elements of the planning, with a solar geyser and grey water system/ rainwater collection points installed. Domestic renewable power (e.g. wind pumps, solar panels) are in their infancy in South Africa but installing these also forms part of the vision for the house. However, as mentioned, the organic construction methods naturally save energy, and the many windows, especially on the sunny sides of the house, also help with passive solar heating (and make the house wonderfully light, without being overwhelming!) In addition, the electricity conduits were installed with a design that largely avoids creating large electromagnetic fields, partly by passing most of the conduits under the ground floor. The design incorporates a more esoteric understanding of energy, using elements of ‘Vastu’ Vedic architectural principles, such as an east-facing front door and a central ‘still point.’

For more on the construction history have a look at
www.cobhouse.blogspot.com