Are you looking for a DIY construction technique for building an affordable earthquake-, flood-, and bullet-resistant home? Look no further.
There are a lot of variations of designs for homes built with earth, from Mike Oehler's classic $50 underground house to rammed earth and adobe, but earthbag construction appears to be one of the most economical options that lends itself easily to DIY construction. Granted, there's a lot of 'sweat equity' required to build one (though probably not nearly as much as an Earthship), but the finished product is considered to be not only earthquake- and flood-resistant, but also bullet-proof, which is something to consider when building your apocalypse-proof dwelling.
Many years ago, after spending a significant amount of time and energy researching DIY home building techniques for a potential off-grid home for my family, I came to the conclusion that earthbag construction would be the best option for our situation, and although the plan to build our hippie enclave out in the boonies fell through (a story for another day), I still think this method of DIY building holds a lot of promise for sustainable, low embodied-energy homes. It's not exactly standard fare for building inspectors and local code compliance, but earthbag construction isn't a brand new technique, and many others have already set precedents in their locations, so getting one approved doesn't have to mean reinventing the wheel (your mileage may vary).
For those new to the term, earthbag building uses bags (often polypropylene grain bags) filled with dirt or other mineral-based materials that are tamped down in place - similar to laying bricks in courses - which creates an incredibly strong and durable wall. It's a bit more involved than that, as you'll see shortly, but in essence, it allows for the use of minimal off-site materials, mostly for the roof (if you aren't building a dome), and windows and doors, and is considered to be one of the easiest methods for the average person to build. It doesn't require huge external energy inputs for tamping (as rammed earth does), or making and drying adobe bricks in advance, and once the walls have been plastered over, it is virtually indistinguishable from any other building.
One of the leading lights in earthbag construction is Dr. Owen Geiger, who also happens to be the former Director of Builders Without Borders, and his book, Earthbag Building Guide, is considered to be an authoritative guide for both the DIY builder and those in the alternative building trade. The following playlist, which is comprised of some 49 step-by-step videos of earthbag building techniques, is well worth watching and bookmarking for future reference.
For more in-depth written instructions, as well as excellent images illustrating each step, see his two Instructables posts, How to Build an Earthbag Roundhouse and Step-by-Step Earthbag Building, and learn more at his Earthbag Building website.