We've discussed the pros and cons of various building styles in our search for the best option for Sabbatical Ranch. Building with earth comes out on top, mainly for health reasons but it also turns out to be quite economical. And there are options that make it very doable for just about any ability level.
What we settled on is Superadobe/Hyperadobe! These take advantage of the benefits of two ancient building styles, with a modern twist.
The late Iranian-American architect Nader Khalili started Cal-Earth Institute (continued by his children) where he invented Superadobe as a way anyone anywhere in the world could build their own home from the earth beneath their feet using only the most basic and commonly available tools. Superadobe began by using sandbags which have long been used in war to build bulletproof cover and in flood areas to build dikes. Sandbags can certainly be used, but they are also available on rolls of tubing hundreds of feet long (sandbags are made from these rolls by cutting to size and sewing an end). Using rolls of tubing makes building go quicker (you don't have to tie off a zillion individual bags) and adds some strength during building. It's also known as earthbag building and now there's another version, Hyperadobe, that uses less expensive mesh bag material (similar to what onions are often packed in).
Adobe mix is put in bags rather than brick forms and is tamped in place (rammed earth) before it dries. The adobe mix is self-supporting once it is set up and the bags could disintegrate, though they won't for a very, very long time. Barbed wire is added between each course of bags to add tensile strength. Mr. Khalili preferred using arches because of their strength and versatility, particularly the pointed lancet arch. It makes the best window and door openings, rotated in a circle it forms a dome, placed in a row it forms a vault, etc. Overall it's very flexible. You have all kinds of options available for your design.
Mr. Khalili worked with an engineer to design Superadobe and got it approved by one of California's strict building departments after having earthquake seismic tests done on it. The Superadobe was so strong that they had to shut off the earthquake-simulating equipment because it was going to break instead of the building. That probably can't be said of any stick-built, mold-prone, paper houses.
Is your earth good enough? You can easily find out with a simple jar test. Dig down past the top soil, usually about six inches, and use the subsoil to fill a clear jar halfway. Fill it the rest of the way with water, shake it up, and let it sit for 24 hours. Sand will settle at the bottom, followed by silt, and then clay - with visibly clear distinctions between each layer. By measuring the depth of each part you can then calculate what percentage of each is in your soil. About 25% clay (+/- 5%) is what's needed for a good adobe mix.
We only have 12.5% clay and since we're not aware of a local source of clay for an additive, we created stabilized earth by adding lime. This turned out to be a real blessing because neither ground critters nor mold like lime. Lime is nontoxic, VOC-free, and it breathes - allowing moisture vapor to escape and naturally regulating humidity. Over time (think decades) it literally turns back into limestone.
Taking everything we learned we decided to get some hands-on practice by building a small bench to start with. This provided some useful experience before we went on to actually build a structure. Here are some pictures of this experiment:
I just gave a basic overview of Superadobe/Hyperadobe building. Obviously there's a lot of details left out. Future posts will show some other projects and I'm happy to answer any questions in the comments, but what I recommend is to attend a workshop or complete the Cal-Earth online training like we did. I have to say I was very disappointed in their customer service. They wouldn't answer the phone but said they would return phone calls during a couple hours one day a week (they didn't). It took them a couple weeks to provide a generic, non-answer reply to one email and they never did reply to a different one.
Nonetheless, Cal-Earth's online training is still better than the websites claiming to have everything you need to learn about earthbag building. I did learn about Hyperadobe from them but I spent entirely too long searching their websites for a lot of unanswered questions. They have obviously not taken Cal-Earth's training or they would have some much better answers. I wouldn't normally share this kind of information but if you're serious about building, it could save you a lot of time.
Dedicated Christian, patriot, family man, founder of Sabbatical Ranch