I've been kicking around the idea of building something out of cob for some time. I have to finish a barn up that has only a roof. I figured cob would be a fantastic material to do it with. My only question that I can't seem to find a definitive answer for is how to build the "good boots" and the foundation. I have searched this forum, I just can't seem to find anything that really fits what I'm dealing with here. Where I live used to be a bean farm. There is a lot of clay in the soil, and when it gets wet, you get taller when you walk around (sticks to your boots that bad, literally!). The only material I have to bring in is sand.
So here's the question: How do I build a foundation for a cob structure? I've seen flat rock stacked, and gravel type things in pictures, but nothing that really addresses what to use, and how to use it, as a foundation. As I said, the soil here has a high clay content. When it dries, it shrinks so bad you can step in the cracks. When it's wet, it holds water. Since it holds water, I know that cob directly on the ground will be a bad thing... might dissolve the walls!
I was thinking of digging a footer way wider than the wall, so it extends out past the perimeter of the walls about two feet to act like a French drain, but I think the first two feet of the wall would need to be something other than just cob...
The region I'm in is in Clark County, Arkansas. The reason I'm considering cob is because of its ease of construction, simplicity, abundance of materials, and to fight the climate! The summers here can be absolutely Hellishly hot! (105+ for a few weeks) and when it rains, it just rains and rains and rains... We are stuck between the moist air from the Gulf of Mexico, and the cool air coming down from the Great Plains, so the weather can change very quickly. I went to work one day at 6 am. It was a balmy 77 degrees, 800% humidity (yes, eight-hundred)... at 3 pm it was 27 degrees and snowing.
We are also kind of outgrowing our cabin now. The kids are getting a little bigger. We need just a little more space. I am hoping to learn enough with the barn and possibly a picnic/tiki kind of area with fire pit and oven/grill kind of thing to be able to build a suitable home. I also have about 9 acres of cedar for structural use (that's what the barn was started with).
And hey, Paul, and all you other Permie Gurus out there, thanks for being there for us noobs and answering our silly, redundant noob-ish questions.