Building an Earth-Sheltered Home: Part III

Enlarge Image Image Gallery The asphalt-bentonite emulsion is applied to the stucco surface with brushes. It's not a fun job. PHOTO: MOTHER EARTH NEWS STAFF

Is is possible to achieve food and energy independence on one acre? Well, with imagination, hard work, and the right one acre, we think it can be done . . .and that's what this project is all about. Of course, providing most of the basic needs for four people from such a small piece of ground is a tall order. Still, we think it's a goal worth pursuing, and we're hoping that in this series of articles about our low-cost homestead we'll be able to help some of you in your struggles to increase your self-reliance . . . by doing some of the experimenting for you.  

In previous installments (see Part I and Part II), we discussed both our plans for the project and the construction of the building's shell. This time around, we'll go over the important tasks of waterproofing and insulation, and also describe a couple of the home's special energy-saving details.  

Effective waterproofing is crucial to the longevity of any earth-sheltered home, and leakage problems have traditionally been the major complaint voiced by owners of such structures. Fortunately, there are numerous quality waterproofing systems on the market today, two of which we used successfully in our last earth-sheltered building construction project (see My Mother's House Part I, Part II, Part III, Part IV, Part V, Part VI and Part VII).

Of course, good commercial waterproofing systems are expensive . . . but, in general, they're probably the wisest expenditure you can make when building an underground home. However, for our ultra-low-cost earth shelter, we decided to take a risky but very inexpensive approach. As an experiment, we chose to use two applications of an asphalt-bentonite compound in conjunction with a layer of 6-mil polyethylene. The total cost of the adhesive and the plastic was less than 15 cents per square foot of wall . . . as opposed to the $1.00 per square foot (or more) price tag on proven commercial systems.