My partner has a lot in North Seattle with a roughly 40 foot wide and 100 foot deep backyard where she hopes that we can build a 20 ft square, two story small home, and rent out the current home.
We have time and energy to do this, and cob looks great, IF it can work for us. We don't know yet about Seattle city planners opinion on this building style, or if we can use our local dirt as the main raw material.
I'd really like to connect with locals that are already building this way, and assist them to build something first.
Please do your homework. Consider saving yourself a lot of headache by hiring a consultant who knows the local laws. A cob cottage in your back yard is a wonderful thing, and before you put your love and time and money into it you need to be clear what the laws are in your community. Buildings are regulated at state, county and city levels. There are relatively few places in the US where there are no codes. A few more have lax code enforcement. Cannon County, TN for instance, has codes on the books but no code enforcement office.
Most buildings require some sort of permission. It is possible that a shed under 180 square feet will not need a building permit but it may still need a zoning permit. Everything else will likely need permits. A good place to start to look for that information is the website for your city or county. Also be aware that unless you live in a very rural or economically depressed area, an unwired, unplumbed shed that you occasionally camp or hang out in will be viewed quite differently by your code officials and neighbors than a 2 story 400 square foot house built on the same property as another (income producing) residential structure. Before you do it make sure whether or not secondary residences are allowed on such a property. If you are lucky no one will care, but find that in writing before you decide what you will do.
Many people have found that the low cost, simplicity and sheer pleasure of having such a structure even just for a little while are worth the risk of having it found out and ordered torn down, but be sure you are one of those people, and not someone who would be devastated financially or emotionally by having your dream crushed. Probably a structure you will live in made from earthen materials will require an engineering stamp to show that the load capabilities have been calculated to meet or exceed standard industrial construction. Probably you will need a zoning variance to allow a second dwelling. Probably you will need to provide energy calculations that show your alternative materials building has sufficient insulation for it to keep you comfortable with reasonable energy costs.
None of these things are impossible but they take time and money and patience with a system that has not been designed to appreciate that small and simple are often better. That low embodied energy, non toxic, minimally refined local materials can be beautiful and safe and cozy and encourage community interaction and green space and lower congestion on the roads and lower water and energy use. These points can be a hard sell to officials charged with keeping an economic status quo. Not impossible but hard. Probably worth the effort, but also probably more effort than you expect. Please keep us informed of your process. All of the goals involved here are shared by a number of us and we want to see you succeed at your chosen level and share that success around as encouragement.
If you want to see an amazing collection of hand-built homes, check out my friend Lloyd's http://www.theshelterblog.com/ or one of his fantastic books.