PSP stands for Post/Shoring/Polyethylene. These are the materials and the system which we use for building our undergrounds in Northern Idaho and, increasingly, throughout the west. Because the materials are different from those used by underground architects in the east we think of our methods as the Western School of Underground Architecture.
The easterners use concrete as a basic building material. (We fondly think of the easterners as Concrete Terrorists.) The easterners use concrete because the resultant buildings will last for centuries avoiding disruption of the flora and fauna on the roof. Some like concrete because the roofs can withstand a greater load. They want to build places that can withstand the weight of trees.
We can't argue with these thoughts. It is certainly desirable to leave the vegetation on the roof undisturbed for centuries. And it is a testament to the degree of environmental concern of underground architects that they should insist upon roof soil conditions which allow the true natural environment and native trees to reassert themselves.
(1) Cement is a non-renewable resource.
(2) Cement is rarely native to the building site. Being very heavy it takes great amounts of energy to transport.
(3) Concrete is too permanent. To knock out a wall or punch through a new window or work on the pipes beneath a slab floor one must rent a jack hammer or hire a crew at great expense.
(4) Concrete is lousy to look at. It has no soul.
(5) Concrete is expensive. Labor costs are high. There is more work (and material) involved in just building the forms for a pour than there is in building an entire wall by the PSP system.
(6) Concrete is a poor insulator. One inch of lumber is a better insulator than six inches of concrete. In many cases then concrete necessitates the additional expense of insulation.
(7) Concrete is difficult for the owner-builder to work with.
Wood is the basic component of the PSP system. Wood is fantastic stuff. Pound for pound it is stronger than steel. It is a renewable resource. It is abundant and can be found on many building sites. It is easily worked and can be milled on the site by the builder with a chainsaw and Alaskan Mill. Wood has warmth, richness and soul. It even smells good.
In the PSP system treated posts are set into the ground after the excavation has been made. Beams for the roof are notched into these. Then a sheet of polyethylene is stretched around the outside of the wall. Shoring is placed between the posts and the polyethylene, one board at a time. The polyethylene is stretched snug, and earth is back-filled behind, pressing the polyethylene against the shoring and the shoring against the posts.
We believe the PSP system is a real breakthrough. Less than half the materials are used than in, say, the construction of a frame house.
While wood is the basic component of the PSP system, polyethylene is the secret of its success. Polyethylene is inexpensive, easy to work with, and readily available. It is an absolute moisture barrier and is what keeps the wooden walls from rotting. While it is true that this plastic deteriorates quickly when exposed to the ultraviolet rays of sunlight, it lasts indefinitely underground. (Environmentalists are concerned that garbage buried in polyethylene bags may not decompose for centuries because it never becomes exposed to the dampness of the earth.) Being new to mankind this material has allowed us to develop a building system which is equally
Though polyethylene is an absolute moisture barrier, it is not fool proof: a small pinprick or tear could lead to really annoying leaks if the structure is not designed and constructed with this possibility in mind. Therefore, one cardinal rule of design must be followed: DESIGN SO THAT ALL WATER MAY FREELY RUN OFF OR AWAY FROM THE STRUCTURE. Never let the water back up against the house, for if you do, sooner or later it is going to find a way in.
The PSP system, being new, has had a field test of only six years at this writing, so we can make no absolute guarantees of duration. The individual components are expected to last well, however. As we've said polyethylene has a life expectancy of centuries underground. Posts treated with Penta were at first expected to last only thirty-five years out in the weather as fence posts. The industry has
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