Steps of Construction
The steps for construction using Composite Shell construction are somewhat different than for conventional construction because utilities are placed in the floor rather than the walls. Therefore, utilities to go in with the foundation. First the site plan must be defined on the ground so you will know where to dig foundations, erect walls, install utilities, etc.
Defining the Site
Rooms can be accurately defined on the ground by drawing simple arcs with a piece of string. For hexgonal rooms, use a string the length of one side of the room (outer dimension first).
- Drive a stake at the first corner.
- Sweep an arc to where a second corner is desired.
- Mark the center (the intersection of arcs from the two corners) and draw a circle.
- From there all corners can be found at the intersections of arcs from the corners and the center.
- Drive stakes at the ends of the "petals". (See diagram at right.)
- Draw the inner wall dimensions in the same way using the common center.
- The perimeter of each room is defined by tying strings to the stakes.
Leveling the Site
Now that the site is defined, it must be leveled. Build up low points with extra soil so that floors are above grade. Earth dug to make solar heating channels (discussed later) could be used for leveling. Leveling is done with a water level, which is simply a long hose filled with water. The hose must be clear at one end so that you can see the water level. Attach a ruler to that end to read changes in soil height.
Using a water level:
- Fix the end without the ruler so it doesn't move.
- Pick a starting reference point (high point) to begin leveling.
- With the bottom of the ruler on the ground, note the water level on the ruler, (or slide the ruler to a convenient mark, such as a zero point).
- When you move, match the water level to the same mark on the ruler. The bottom end of the ruler is once again at the reference height.
- Mark this reference height on several stakes patterned in a rough grid within the site. Use the bottom of the ruler to draw a line on the stakes.
- Dig, fill, and rake until the site is level as shown by marks on the sticks. Each room must be level, but adjoining rooms could step to different heights.
In mild climates, the perimeter foundation only needs to be about 6-8 inches deep. In cold climates, the foundation should be dug deeper, 12-18 inches. It doesn't have to go all the way to freezing depth because it will be insulated and heated. It's insulated from the surrounding earth both to prevent freezing and to retain radiant floor heat (solar derived). Perlite-cement 6:1 is a good material for subsurface insulation.
For structural integrity the wall foundations may be rammed until the earth at the perimeter is rock solid. Trials need to be made as to whether a rammed earth perimeter foundation will last. Historical data would be helpful from those parts of the world where this may have been tried. Otherwise, conventional poured foundation walls of concrete with reinforcement are suitable in developed countries.
Gravel foundations, sometimes known as floating foundations, have proved very successful, even for very heavy walls such as adobe. Most foundations in western countries are overbuilt. Obviously, the gravel can only come up to grade level without spilling over, so a rammed earth, stabilized earth (with 10-15% cement), mortared rock, or concrete layer is needed on top to divert flowing rainwater away from the wall.
One easy way to make the foundation is to make it integral to the wall as it is being constructed. When the forms have been tilted up and the gravel foundation is at the edge of the form (as shown to the right), the wall and foundation can be sprayed with ferro-fiber cement at the same time, making the foundation, wall, and roof in one process. Whole rooms are created at once with six-sided forms.
The utility system consists of four main systems: electrical, hot and cold water, drain water, and heat. These systems may be laid into the earth at the same time the foundation is being constructed so that external connections can pass through the perimeter foundation. Or cutouts may be inserted into the perimeter foundation for later construction of the utility systems.
Heat channels, which connect to flat plate solar collectors, are constructed first because they are deeper than the electrical and water channels which are overlaid on top. In each room, concentric channels are dug a few feet apart and an incoming and outgoing heat channel links them all as shown in the diagram. Solar panels heat the earth under the floor for space heating. The perimeter of the foundation must be insulated to retain the heat (perlite-cement).
Other Utility Channels
Shallower channels are then cut for the following, (in order):
Utility systems are discussed in the section: Life
- Drain water -- drain pipes from sinks and showers to holding tanks. (It will be used for sub-surface irrigation of plants.)
- Water supply pipes -- hot and cold (from where they are needed to the hot and cold water distribution center).
- Electrical wiring -- from the corners where electrical outlets will be placed to the electrical distribution center and from outlets to switches.
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