Hi Brian, my company specializes in clay based material engineering and we’ve worked regularly with rammed earth and watershed blocks as well as cob, adobe and other clay structural wall systems. I’m happy to answer any questions you have, feel free to reach out via my contact info below. Though I can answer some of your questions here.
Bay area builders: You obviously know of Rammed Earthworks who are excellent, and there are other natural builders in the area with rammed earth experience including Massey Burke. I could likely generate 3 or 4 other names.
Cement/stabilization has a lot to do with the rest of your questions. Most convectional rammed earth contains a notable amount of cement or asphalt emulsion stabilization. This is not required though has it’s practical benefits as cement usually does concerning structural characteristics and durability against weather. To directly address question 1, you design to minimize cement use by basing your walls after the traditional methods. The less cement for any clay based building type, the more structure and durability will effect architectural choices. Question 2 and 3 depend a lot on your cement/stabilization.
We’ve used watershed retaining below grade many time and simply protect it with appropriate drainage and vapor barriers as you would any concrete wall. A concrete toe is used at the base.
Feel free to reach out and best of luck,
Anthony
814-502-6001
anthony@verdantstructural.com