PSP (Post/Shoring/Polyethylene)

Mike Oehler is the author of The Fifty Dollar and Up Underground House Bookwhich describes his PSP system of building underground. Mike lived in an underground home of his own design for over twenty years. He evolved some very well thought-out concepts for designing underground structures, which could also be used with other construction techniques. PSP stand for Post, Shoring, Polyethylene---the basic, rather low-tech approach to using posts, boards and plastic sheeting to build underground very inexpensively. Mike also produced a video series that demonstrates his concepts. He died in 2016.

undergroundhousing.com This links to information about Mike's book and videos, presented by the publisher.

Questions and Answers

Comment from Mike: I'm building a new underground house/tree house, Kelly, and have been working on it for two years now. It should be spectacular--my reply to all those who wouldn't consider my methods because they were too small or cheap.

Q: Has anyone used bags full of leaves, sage brush. on to top of an underground house??? such that you get insulation.. toped by PE film and with perhaps 2" of sand on top to protect the PE film?? In this way you keep the weight down to very little. The garbage bags would form a tight seal.

A: I know of no one who has used bags of leaves or sagebrush on top of an underground house, though the idea is intriguing. Yes, it certainly would cut down on the weight and provide excellent insulation. I see some probable difficulties, however. One is fire danger which is absolutely not a factor with solid earth. Another is that the material in the bags would likely poke through with the weight of the sand on top, certainly through the garbage bags, possibly through the poly sheet on top. And of course you do need something on top to protect the polyethylene from the ultraviolet in the sun's rays which means weight. I wouldn't advise walking on that roof either which also means keeping the dogs and kids off, a big order. Possibly the swimming pool liner material EDPM (I think it is) would solve this problem. I'll be using EDPM for one of the layers on the Ridge House this spring. Try your idea and let me know ten years down the line how it worked. Nice question.

Q: Thanks for getting back to me.. I'm thinking as sloping the roof towards the center of the circular building.. and collecting the water in the middle.. But instead of bags of sage brush.. Bags of plastic bottles.. Covering the roof with that..then.. a plastic tarp and a little sand or maybe just use 1/2 fill bottles with sand to stop them from blowing away.... maybe painting the top bottles white..How about that??? Has anyone used capped bottles in the wall for partial insulation??

A: (Kelly) I would have some concerns about the weight of the collected water, as it can be VERY heavy. The plastic bottle idea also might work. I have heard of the use of glass bottles in walls for light and decoration...and some insulation. Let me know how it all works out.

Q: If I use Mike Oehler's method of building underground, can I have a bathroom, bathroom shower, washer/dryer, or just plain running water in the house without having to build a story above ground ?

A: Most likely yes. Depends on the depth of sewers, bedrock, water table. In almost every case you can do it if you build on a slope. Adding plumbing to an underground house is no different than adding it to a basement laundry or rec room.

Q: I am wanting to build a pit type (in ground) greenhouse, but can find virtually no real useful info on one. Building it is not the problem, I am a carpenter, but is it a good workable type of greenhouse. I have heard they are very energy efficient and I have heard they are difficult to grow in, so I don't know. What I want to do is to grow carnivorous plants, which require a fairly humid environment, with plenty of sunlight, yet keeping temperatures in the high 80's would be ideal, as well keeping winter temps in the high 40's. I have a traditional attached greenhouse on my home, but heating it at all in the winter is expensive, and summer overheating is always a problem. So, I have heard that pit type greenhouses need very little if any heating or cooling, if so that would be the answer to most of my problems. If possible, I would like to even grow some vegetables in it during the winter as I have heard can be done. Now,, I live in southern Virginia, I have full access to the summer and winter sun, and have anywhere on a 5 acre plot to put this greenhouse, and would plan to run water and electric to it. So, if you could PLEASE just give me the rundown on this idea, the good and bad, so that I can decide on what to do I will truly appreciate it, very much.

A: A pit greenhouse should do very well in Virginia on either a south slope or flat land. I've had them on both up here next to the Canadian border and they have taken my tomatoes into the second week in December (every unsheltered garden freezes out by the first week in October here) and takes such hardies as kale and cabbage through the winter. They don't grow for two winter months but are still alive and can be harvested. All this without heat other than the sun and earth and no thermo-pane glazing.

My secret is that on the south wall of the greenhouse I dig a pit down eight feet and build a walkway up four or five feet where I can walk and bend over the growing beds to work on the plants. The pit allows cold winter air to flow downward to be heated by the earth rather than lying on the plants. On flat land I'd sink my north wall and all the grow areas about four foot deep and pile the earth up on the north side leaving at least a foot of north wall exposed for ventilation "windows" that can be opened as needed. I'd put some rigid foam insulation over that mound of earth on the north and a layer of polyethylene to keep it dry and some inches of earth to protect the poly from the sun. That north mound will serve as a heat sink then, to radiate heat back into the greenhouse at night.

Hard to advise you on the south slope since I don't know the pitch of the slope, but again have the north wall come up a foot to two above the surface for ventilation hatches. Always pitch your glazed roof towards the south, of course. You may get away with single glazing in Virginia. My next greenhouse will have a southern wall of used thermo-pane sliding glass door (stationary) which I've gotten for as cheap as $5 used ($300 & up new.) I'll probably glaze the roof with duo-pane greenhouse fiberglass except the very north four feet which will be in hinged plywood which I can open in the summer. I'll insulate the plywood for the winter I expect to incorporate rabbits and chickens into the greenhouse for body heat, CO2, ammonia and manure. They'll have automatic access to a pen on the outside. All earth level grow beds and critter cages will have wire mesh buried a foot deep to keep the right critters in and the undesirables (weasels, gophers) out.

Q: What is the deal on Radon gas. Mike seems to say its from the granite in the concrete floor. Is that true. I assume the PE film would help to keep it down.. But has anyone done any radon studies in his underground home??

A: No one has done studies on radon in my home because my home is so well ventilated. It also has no concrete in it. Radon is produced by the radioactive breakdown of granite, so I'm told, which comprises much of concrete.

Q: I have just ordered you book, but I'm curious if the ideas can work for North Texas soils. Absolutely no one in Texas has basements except big banks, and home foundations are regularly damaged by expanding and contracting soil.

A: Excellent question. DISCLAIMER. I HAVE NEVER BUILT IN EXPANSIVE SOILS SO HAVE NO FIRST HAND EXPERIENCE. THE FOLLOWING IS GUESSTIMATE: I think the consensus among underground architects is that if you feel you must go underground in expansive soils excavate a vertical crawl space between the walls of the structure and the soil. Extend the roof out a couple of feet over the edge of the excavation. Be sure to allow for the angle of repose of the soil (the angle at which the soil no longer crumbles down.) Or build above ground and berm up and over. Insulate the bermed earth a foot under the surface and you have a heat sink in the winter and a cold sink in the summer (open windows in the cool of the night then.) I always advise building a shelter first close to where the house will later be built so they may be connected. Do your experimenting and make your mistakes on the shelter. It should have the vertical crawl space, of course.

Q: Mike, do you think using 4x4s for posts and plywood for shoring work? Logs just aren't easily available in the desert. I would keep the fill on the roof to like a foot.

A: I am not a structural engineer and so this is only a guess and it may be a bad one. I'd take your questions to such an engineer. I suspect 4x4s would work for posts with a light dirt load on the roof but not for the girders and beams. To lighten the roof load further cut that foot of earth to six or eight inches and beneath it use some rigid foam insulation to insulate away from desert extremes. Plywood out-gasses chemicals. Sure you want to use it? Have you tried salvaging lumber? You should definitely be looking for used windows, too.

C: Thanks for the reply. I was trying to come up with locally available building supplies; logs are kinda hard to come by out in the desert. I considered old light poles or railroad ties but they're kinda nasty and treated with chemicals. I even considered walls of chicken wire covered in a plaster of sorts. I guess buildings in the west are just too new for much salvage.

Q: I am considering building a large PSP 2+ Story garage/barn into a hillside up in the mountains of Colorado. Our forests up here are increasingly beetle killed and needing to be removed. Do you think that these trees are still structurally sound both as poles and as underground siding? (Of course I will be using a waterproofing material prior to backfilling)

A: Sure. Most insect kill is due to their action in the bark. Carpenter ants and termites bore into the lumber part of the tree, but I doubt any beetles do. Drop a tree and do some exploring into the interior and edges of the logs to see where the damage is. But, yeah, I'd encourage you to use the material for PSP. Incidentally I've begun using EPDM for waterproofing on my roofs and am highly impressed. May try it on the sides next.

Q: I am considering building my own home, in the research phase, and am intrigued by your PSP concept. It is very interesting how simple your system is, and I am heartened that others have built such beautiful homes. I have devoured your book and was wondering if your Ridge House was ever completed. Your website as well as your book states it is under construction.

A: Not yet completed due mainly to lack of funds since we are expanding into Internet Protocol Television. Returnees from last years Building School, this summer's students and actors from one of our television productions will be finishing that and a couple of other projects on my land this summer with me, funds and God willing. People qualify for our summer building schools when they buy and understand our Underground House Workshop and Shelter tapes. Info at www.undergroundhousing.com.

Q: I live in northeast Texas near the City of Clarksville. Our soil is an expanding clay that can be a challenge. Over 20 years ago I started a house project that was, for lack of a better term, a partially sunken underground pole barn. The idea was from a book by an Idahoan named Mike Oehler. It incorporated a dirt floor with plastic sheeting and carpet stretched over it. Really a basic building. The ceiling was large timbers and the walls were wood with plastic behind the wood to seal from the dirt. In trying to construct this dwelling, I used treated (penta) posts and oak timbers. Or at least I thought it was oak; an unscrupulous sawmill operator sold me sweet gum instead of oak, so it rotted before we could do anything. Now I have the site with no timbers and 33 posts standing. The original plan has problems, the cost of large timbers, the plastic sheeting causes moisture behind the wood, resulting in rot. With costs of building so high,

I had considered some type of dirt, cement, and straw type building blocks for the walls. The roof is still up in the air as to what to do to it. If you have any ideas what could be done I would appreciate it. We have got to do a better job with out houses, and it looks like you have done some excellent work that is energy efficient and does not waste our resources like conventional construction.

A (Kelly): For any portions of the house that will be bermed, or underground, I would recommend the use of earthbags or some masonry material, such as stone, lightweight concrete, etc. that will not be vulnerable to rot. The rest of the house could be almost anything, although insulating materials are better, such as strawbales, cordwood, or earthbags filled with crushed volcanic rock.

Q: I am very interested in building a PSP home and will be purchasing Mike Oehler's book. However, I was curious if it is possible to build this type of home in Northern Ontario which is in Canada. Some winters we get a lot of snow, and it can be very cold. My concern would be the weight of snow on the structure as well as how well an underground greenhouse could stand up to a Canadian winter.

A: Depending on soil conditions it should indeed be worthwhile to build underground and earth shelter greenhouses in Northern Ontario. We had a our winter of '97 here in Northern Idaho had 13 to 18 feet of snow. The national guard was shoveling school roofs  (one collapsed anyway) Some garages and barns went down around he county and on my land two car roofs and a thirty year-old milking shed had their roofs collapse. But none of the six underground structures on my land were injured, and I only shoveled part of one one time. An earth-sheltered greenhouse is exactly what you need for your country. It will triple your growing season, possibly give you a year-round harvest. We'll have a book out on that soon -- "The Earth-sheltered Solar Greenhouse Book." Meanwhile "The $50 & Up Underground House Book" is where you start for underground housing. When you are definitely committed, "The Underground House Workshop and Survival Shelter Seminar" DVDs are a must. undergroundhousing.com, or 800 328-8790 for information.

Q: Could steel I-beams be used to make PSP underground homes with larger free space?

A: (Kelly) I see no reason why you couldn't use steel I-beams to construct a PSP underground home, especially if the details of construction kept the steel from possible rust.


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