Shelter from the elements is critical to human survival. Settlers on the American frontier in the 19th century built with what they had at their disposal. The log cabin leaps to mind, but on the Plains there was little wood with which to build, so sod dwellings were more typical. There is a common characteristic that links frontier shelter designs, regardless of type. They must be constructed with the materials on hand and with the tools the settlers can carry with them.
What dwelling might a 21st century frontiersman build? Gasoline-powered tools and other technological improvements would make log and sod houses easier to construct and more livable, but they also make possible underground shelter types that were not widely practical previously. Ordinary polyethylene plastic sheeting is the key to a comfortable, dry, inexpensive underground frontier homestead. Contrary to what one might expect, living underground doesn’t have to be like living in a basement. These dwellings can be bright and airy and still have the benefits of exceptional energy efficiency, durability and low maintenance, quiet, and, perhaps most appealing in today’s intrusive modern world, they can disappear into the landscape.
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I unintentionally began research for this article 30 years ago when I discovered a book intriguingly titled The $50 And Up Underground House Book by Mike Oehler. It turned out he was the man who pioneered modern do-it-yourself underground housing in America. He began experimenting in 1971 in rural Idaho. The cost of that $50 house was in 1971 dollars and Oehler was a model of frugality that would make my Great Depression-era grandparents look like spendthrifts. However, his approaches were so novel and seemingly easy I found myself saying, “I can do this!”
His dwellings are manly and rustic, as one would expect from a guy who has killed four bears, but they can be finished in whatever manner suits the builder’s tastes. The important part is Oehler’s basic uphill patio design and his PSP construction method, which together ensure a dry, strong, remarkably long-lasting dwelling. PSP stands for “Post- Shoring-Polyethylene.” Assuming there are suitable trees on site to cut and mill, this dwelling can be built with a chainsaw, a portable Alaska mill for cutting boards, a shovel, a hammer and a utility knife to the cut the plastic.
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Choose Your Site
For an underground house to be dry, it must be suitably above the water table and well drained. Sandy soil is best for drainage and clay is worst. French drains can convey water away from the underground structure’s walls in clay soils, so don’t give up dreams of an underground bungalow if you are stuck with that soil type.
Working with nature to assist drainage is one of Oehler’s main design points. His house is like an underground lean-to built into a hillside, with the front facing uphill into a unique terraced patio above. Reversing the orientation of the underground house in this way solved the most important problem faced by underground builders: water drainage. Rainwater runs down the sloping, earth-covered, shed-style roof and continues on down the hillside. Rainwater that falls on the uphill patio is also drained away downhill and never has the chance to pool up. Downhill views need not be sacrificed either. The inclusion of a conventional gable, or the unique Sunscoops and Hollywood Wing of Oehler’s own invention, bring in an abundance of light, air and vistas.
Consider the alternative outward-facing underground house and the genius of this approach becomes apparent. Lateral soil pressure can be extreme. How many bowing or collapsed retaining walls have you seen? It is even more extreme on a hillside. My driveway is on the edge of a hill and shows ever-enlarging cracks year to year as nature slowly works to flatten the land and pull my driveway down with it. Add to this hydraulic pressure, which is much greater than soil pressure, and you can see why a house built facing downhill with its underground back wall on the uphill side is a poor design choice. Nature is trying to force water through that rear wall with all her might.
The simplest form of Oehler’s house design has windows and an entry door only on the uphill side. It is naturally concealed and has a certain clandestine, outlaw hideout appeal to it. However, Oehler demonstrates that builders can find advantages by digging window openings to allow for more light and cross ventilation. They might also open up one side of the house to permit down-slope access, rather than climbing down into the house from above through the uphill terraced patio. This house design is also adaptable to flat land.
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The building process is straightforward. After finding a suitable site and addressing issues of drainage specific to the soil type, you start digging. If your site is in an out of the way, inaccessible location, you will need to do this by hand with your shovel. If the location of your underground house needs to remain secret, you’ll be digging alone. If not, enlist the assistance of friends.
As a baseline, consider that it took Oehler three weeks of digging for six to eight hours a day to do the excavation for his first 120-square-foot house by himself. In the process, he refined manual excavation to a precise science of economy of motion.
Once the excavation is complete, the dirt floor must be leveled in preparation for the installation of the vertical posts that support the weight of the roof. Oehler has used tree trunks with the buried end fire-charred and wrapped in ordinary plastic garbage bags to stave off rot, but other materials of similar strength can be used. He now recommends the posts be set in concrete, or at least on a large flat stone to distribute the weight of the roof over a larger area and reduce settling of the posts over time.
After the posts are in straight, leveled and notched, log girders are added running front to back, overhanging the front of the house a bit to keep rain away from the door. Then smaller log purlins are run transverse along the girders. On top of these, roof boards are nailed from purlin to purlin.
Next the walls are constructed. A long sheet of polyethylene plastic is wrapped loose around the exterior of the posts in the excavation and held in place slightly below floor level by the first wall board. That first board is carefully leveled and nailed in place. Then the gradual process of backfilling begins. To prevent puncturing the plastic, place folded cardboard between it and the backfill. The backfill pins the plastic to the back of the wall board and the wall board to the back of the poles. Add another wallboard on top of the first and repeat the backfill process. Keep doing it until you reach the top. If additional drainage is desired, backfill by first shoveling in a band of sand next to the plastic and then a band of gravel outside of that, then backfill the remaining space with soil.
When the walls are done, it’s time to finish the roof. Builders paper is applied over the roof boards, and then the first layer of polyethylene plastic is carefully laid out so as not to puncture it. It will be held in place by a 4-inch layer of dry, sifted soil, free of sticks or rocks. Then a second sheet of polyethylene is laid over that and additional soil added to taste within the engineered load-bearing capability of your particular roof.
Tables are provided in the book for these important calculations. More soil means more insulation and that first dry layer is particularly important. The exposed soil needs to be graded so that water runs off and away from the house in all downhill directions.
I have not mentioned electrification or plumbing, but both can be easily installed at the appropriate time during the above process. A bonus of living underground is that your buried pipes will never freeze. Once the walls and roof are on, the rest is mostly finish carpentry and interior floor work to suit each builder’s needs and tastes.
Ever since I first read about the PSP method, I wondered how long such a house would actually last. It turns out Mike Oehler is still alive and well and living underground, and I found him through his website at undergroundhousing.com.
He gave me an update for this article. He was quite frank that he only expected the original structure to last seven years. It has now been in use for 46 years and is still sound and dry.
The polyethylene sheeting remains impervious to water and he speculates that its longevity underground, away from the destructive effects of UV sunlight, may be indefinite. What few leaks he had early on were due to design and assembly errors he has since corrected and incorporated into the PSP method.
Wood rot and pest damage were concerns of mine, too. He informed me that on his original house, he replaced the front posts for rot at the base only once, but the rot was due to rainwater infiltration and not ground moisture. An engineering error that left the girders exposed to the weather caused water to run down them and then down the vertical posts. His revised design corrected this by extending the shed roof out to the edge of the girders with the plastic draped over the top, forming a drip rail over the patio. He also used bigger posts than were structurally necessary in his revised design. With a bigger post, chances are you wouldn’t live long enough for it to rot significantly. When it does, your heirs will have the relatively simple chore of digging them up and replacing them.
Every house, above or below ground, needs pest protection. Termites and carpenter ants can be addressed in the conventional ways. These pests love moist areas and a dry underground house isn’t particularly inviting, but some will surely come. Oehler found that over-the-counter barrier repellent sprays deter their entry in those areas you can spray. The underground homeowner needs to be watchful just like any other homeowner.
A greater threat to the integrity of the polyethylene sheeting is the gopher and other burrowing animals. Oehler finds that the using 6 inches of gravel for your French drains around the house also effectively blocks them. They are not hard rock miners after all. He has also successfully used buried 0.25-inch galvanized steel mesh. Even with no other treatment, the zinc-plated steel will last a long, long time.
The PSP construction method and uphill patio design now have a track record of success approaching the half-century mark. They can still be built for absurdly little money and in places where conventional homes would present monumental challenges in materials transportation. For the new frontiersman looking to get off the grid or downsize and simplify life, PSP houses are cost-effective shelter solutions.
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This article was originally published in the AMERICAN FRONTIERSMAN ™ 2015 issue #174. Subscription is available in print and digital editions here.