I live on a farm in the country. We have an abundance of dirt. So much in fact that we've contemplated building a house out of cob. It's a natural building material made from dirt, sand, and straw. It's one of the world's most common building materials and has been widely used in England for centuries (think traditional English cottage, more along the lines of an adobe structure, but more weatherproof). They're resistant to rain and, unlike wood structures, regulate their own heat, making them ideally suited for both very hot and cold climates. Living in Wisconsin, both heat during the summer and snow during the winter are factors.
As a starter cob structure, we're thinking about building a cob chicken coop. We're planning on getting 4-6 chickens in the spring and I'm in the preliminary design stage for the coop. I'd like some input on the structure/maintenance and would love to see what other people have done! I can find a lot of great information on building cob houses, cob ovens, even cob bathtubs. However, I've found virtually nothing on making cob chicken coops!
I've tried searching the forums here, but haven't found much. A lot of people that I've come across have worried about how to clean a coop that's predominately made out of dirt. However, cob is water resistant. It can get wet. One of the main differences between cob and adobe structures is that cob structures are more weatherproof and can be made even in places with heavy wind and rainfall. It can even be stuccoed and painted or coated in a lime-sand plaster for greater durability.
There's also a common misconception that they're cold and damp. However, cob structures regulate their own temperature. They trap less condensation than wood structures and don't have the same issues with mold, mildew, rotting, or pests that can sometimes be a problem.
The biggest issue that I can think of would be that the walls are very thick (typically 2 feet). However, smaller structures, like a cob oven, can be as little as 4 inches. I'm not sure how thick they would need to be for a chicken coop, but space isn't that big of a factor. I'd prefer not to build something too big, but we do have the space if we need to.
Some people have suggested putting chicken wire inside the walls to keep predators out, but that seems a little much. We live on a farm surrounded by other farms, so there's very little in the way of large predators. Our biggest issues to chickens would be hawks and stray cats, neither of which I see breaking through a 2 foot thick wall.
I am, though, debating over whether it would need to be built off the ground like a lot of coops are. Of the very few cob chicken coops that I've come across, most of them appear to be built more like a small house or shed where they aren't built off the ground. A lot of coops do so to help deal with rain, heat, and pest regulation. However, none of those are as big a deal with cob structures. We aren't planning on living at our current location forever, though, so I've thought about making it on wheels or otherwise moveable in some way. That would maybe mean that I'd have to build it off the ground.
There's a lot of flexibility with cob structures, though. Even after the cob has dried you can add on, cut out, or reshape the structure, so if something doesn't work or needs to be expanded upon, it's possible to go back and change it later. Since there isn't any wood or other structural confines, there's also a lot more flexibility with nonlinear shapes and sculptural designs. One of the reasons that I'm so drawn to cob is that you can do such interesting things with it. A lot of cob structures are round or dome shaped.