The current challenges are:
1) Finding clay that can work for our earth plaster walls. We currently have 2 tons of clay that is recycled from a pottery shop near our build site. However, we need to find 10 more tons of clay (that will pass our rigid testing) by the beginning of September. We are confident that we'll be able to find it and have some good leads. We should have this sorted out in the next two weeks. By the way, the typical ratio of clay to sand is about 30~70 or sometimes 35/65, but it depends on how the tests go. Other items that are added to the plaster are straw and a binding agent. One thing that we keep coming up against in Japan is the fermenting process that everyone is accustomed to here for the binding agent. Of course, there is a lot of historical evidence to cultures using different fermenting processes (including those that use feces and other foul things from both animals and humans), but in North America this has not been a common practice. Instead of the fermenting process being the "binder" (or adhesive) for the mix, we just add some carpenters glue that works just as well.
2) Deciding which way to go with the final exterior coat with regards to protecting the walls from moisture (the "good coat" that I referred to before). Most people use either cement, lime or a mixture of both in climates like this where a little extra is needed in that final coat to protect against Mother Nature's force. We were thinking Lime, but were not excited about the tedious process of the application and extra care it requires. We have recently found another product that might work nicely. We are ordering a sample up from Tokyo and will test it out. If it passes, it will be much easier to apply and then maintenance will only be about once every 5 years. Not bad at all!!
We'll keep you posted on these two challenges as we progress on attacking them over the next couple weeks.
-Bomber, Maiko & Toby