Just got the photos from Andi of the cob sweat lodge that I mentioned in the previous post...
Andi really pushed me into an experimental mode that I'm not always comfortable in as a builder. The dirt in the cob is just the topsoil that we pulled off the site in the initial excavation. I was worried that it had too much organic matter, and too little clay, but Andi wouldn't budge on her decision. It seemed to make a fine cob, and I'm glad we tried it!
I was also (and still am) concerned about the hurried foundation. It's just a bunch of big rocks laid about 1-2 inches below ground level. It's a healthy, good-natured sort of concern stemming from my past experience with foundations. For the cob cottage in North Carolina, I spent 2 months excavating and digging/filling a drainage trench, and another full month with Mike laying the stone foundation. For Andi's sweat lodge, we spent 20 minutes digging, and then 45 minutes laying the stones.
That being said, this is a perfect structure to experiment with. The worst that could happen is that it cracks over time (with the ground shifting, and frost heave), and falls in on itself. The materials are all natural, and will just return to the earth.
Clay slip was applied to all of the foundation stones as a "glue" before the cob went on.
It was great to feel the mud of Iowa on my bare feet for the first time; I will admit that my toes were desperately frigid by the end of each mix.
We took some handsaws with us down the hill to the magical willow tree and harvested some of the most flexible, straight branches. With even spacing around the circular shape, the branches will be stuck down into the cob; then they will be bent up into a dome shape, and Andi will weave slip-straw (bundles of straw coated in wet clay) between this framework. This will provide the shape and structure of the form, and then a layer of cob will be applied on both the inside and outside faces of the dome. Photos of this process some day soon.
I love the site that Andi chose for the structure. It's just off the main path that extends across the meadow and through the stand of trees that you see in the photo. There are five or six trees that form a circle around the sweat lodge, almost as if they were asking for a circular mud friend.