Thank you, I am very pleased for recognition of this off grid, rammed earth building , where I designed and built the house, energy & water systems and sewerage.
The award-winning rammed earth Otto cottage in Maun, Botswana. Designed and built by Paul Marais. Photo courtesy of Paul Marais.
How did you first get involved in natural building?
I have been always interested in natural buildings and as a student studied natural building in Malawi and Zambia. I have travelled a lot in remote Africa and have an interest in indigenous architecture which is both material and energy efficient. Continue reading →
This post first appeared on Earthworks Magazine in April 2016. We are re-posting it here with the permission of Young Africa Publishing and author Mary-Anne Constable.
House Freeman is cool in the hot Botswana desert thanks to an evaporative cooling system, which draws air over solar powered sprinklers, a living roof and thick, thermally efficient walls. The shuttering was reused in, for example, the roof, so nothing was wasted.
Of more than twenty different types of earth construction techniques, rammed earth has been lauded for its durability, sophisticated environmental performance and striking earthen beauty.
Rammed earth construction in South Africa has generally been stigmatised as a substandard and primitive building construction method reserved ‘for the poor’. Yet it is now gaining popularity for community social projects, as well as among wealthier clients. Although a building standard is yet to be formalised in South Africa, the rammed earth industry is established in many African countries, Europe, United States and Australia. This means plenty of expertise and established international building standards already exist and this construction method is now far removed from its primitive roots.
Foundations for conventional building have, to a large extent, a one size fits all approach regardless of the type of ground you are building on i.e. a concrete and steel foundation that works equally well on all types of earth and varies only slightly in its design. It requires little thought and has been proven to be effective. The cement in concrete provides the compressive strength, and the steel tensile strength to resist cracking. It does however come at a cost to both your pocket and the environment.
When building with earth your foundation needs to be well considered as the integrity of your building rests here. Decisions you make about your foundation depend on the materials you have available, the type of ground you have to build on and what carbon footprint you want to leave. The goal should be to create foundations that are hard enough, move uniformly and resist cracking for the walls above it. Foundations will always have a higher Mpa value than the walls, however it does not need to be excessive. A 4 Mpa foundation is sufficient for a 1.6 Mpa mud-brick wall, which most types of foundations are suitable for. Furthermore, if after levelling the site the undisturbed earth is hard enough, foundations may well be unnecessary.
There are several strategies for foundations depending on the type of ground that you are building on. In this blog post, I discuss the four types of ground, (1) uniformly hard, (2) uniformly soft, (3) hard and soft, and (4) clay, their challenges and several strategies you may incorporate into your design. The discussion is quite technical in some areas so I recommend that you read my three-part series on understanding earth first. Continue reading →