Foundations for Adobe?

Question: How do you build foundations for an adobe house (2 floors) on the sand? The location would be on a stable sand dune. I don't know yet if there's any layer of rock at a decent distance from the surface. But, in the case the layer is very deep, what can we do?

Answer: Sand is not such a bad base for a house. The foundation needs to get down to the frost level if there is one at your location. The foundation needs to be a minimum of 8-inches thick and should be at six-inches wider than the wall on each side. For two story construction the first floor needs to be at least 14-inches thick and the second should step back to 10-inches. Adobe walls should not go higher than ten times their thickness so if the wall does not step back for the second floor then it needs to be twenty-inches thick all the way up. My best recommendation is to stick to a single story if you have not built adobe before and given that you are on a sand base.

Question: If one followed the 10 to 1 width/height ratio, could we build a relatively self standing adobe wall (used like a fence) at the heights mentioned? We had learned that if building a cement block wall of over 4 feet tall, one has to reinforce with mortar & rebar. We would also love our 'wall' to have some curves. Thanks for any hints on reading material and whether homemade sun baked adobe bricks would support this wall project.

Answer: It will work just fine. Just stay a bit below the height limitation of a 10" or 12" wall. A good foundation to the frost line or else a Frank Lloyd Wright gravel trench with or without the concrete grade beam will work. Curves in the wall make it stronger. We do have an adobe discussion group at I normally don't recruit for that group but you might benefit from it more than most.