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