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earth • ship - a dwelling designed to bring people into a more intelligent and sustainable relationship with their environment
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02.19.05   Time Warp

A lot has happened since the last installment. I'm starting with the most recent developments, and if you want to fill in the gaps for yourself you'll want to see the previous entries for the same date. Unless otherwise mentioned, the techniques used in this building project closely follow those outlined in the Hut Video (available from Earthship Biotecture in VHS and DVD).
Excavation:
I got very lucky with the excavation, getting down 5 feet without much contact with the heavy basalt typical of my area. There were a couple of stubborn caliche deposits right at the bottom, but nothing to be frustrated about. This was going to save a good deal of work, except for figuring out what to do with all of that extra earth! That would make for one hell of a berm.
Earthbags:
As you can see, the hut started out with earthbags, but after some experience with them I decided to switch to tires. The bags were pretty impressive, but they seemed to absorb some water and heave a little after a rain, making it necessary to recompact and level them. I also decided that I preferred the substantial feel of the tire and the way they would naturally grip each other. The tires will also provide more relevant experience going forward.
All in all, I don't believe the earthbags have anything on the tires in terms of time. There are probably 4 or more bags to one tire, and after you've sealed them up some how and added some barbed wire between each layer, they can go pretty slow. Of course, a bigger bag may have made a difference.
To seal the bags, I poked holes in them (polypropylene rice bags) with a nail and pushed cable ties through them. The ties made for a reliable seal. I had tried both folding the ends under and using a staple gun but wasn't pleased with either technique. The ties really held on under compaction and made for a very trustworthy brick that I could manipulate. That came in handy when I decided to repurpose the bags for a different project.
The earthbags were misprinted rice bags purchased from The American Bag Company in Grand Junction, Colorado. A palette of 1,000 bags cost me a little over $300 including shipping and there is no end to their unexpected usefulness.
My Tire Pounding Strategy:
The tires went faster than I thought they would. I used empty earthbags to cover the inside gap between tires which worked very well. They bulged out a little which helped to interlock the courses. To speed the tire pounding process and relieve strain on my lower back, I developed a personal technique that involved cutting around the tires about halfway between the inner lip and the topmost arch of the side. I was able to do this rather swiftly using a sharp utility blade, so long as the tires were not double-thick. Being able to keep my back straight greatly extended my tire pounding endurance as well.
With the added reach the shorter lip provided, I was able to get a heavy tamper close enough to the edge to compact the earth tightly into the wells. There was enough of a lip remaining that there was little if any deformation of the tire shape, and once the tire was completely compacted I noticed little difference between its behavior and that of an uncut tire. I could stand right on the edge of these with only the little bit of give you would expect.
One caveat... I felt comfortable with this knowing my tire wall was going to be only 4 or 5 courses high at the most. If the wall needed to be significantly taller I might not cut the tires, anticipating that any added flexibility from the cut tops might translate into a liability with dramatically heavier loads and the greater range of wiggle caused by the height factor.
So tires it was. In addition to covering the gaps, the bags came in very handy as half-blocks and gap fillers. A very effective alternative to cement.
The Door Buck:
Did I ever mention how much I despise wood as a building material ? I do. I love the way it looks. I love the feel of it, but to my mind it is unforgiving and temperamental. No storage technique I have used ever seems to keep it straight, and even freshly bought pieces are a real gamble. It took two tries to get a door buck square enough for my satisfaction. The tricky part is fitting it into place in the door gap between the tires. I attached pieces of metal lathe to the buck and shaped them around, securing them to the tires. Instead of filling the void with cement and filler materials, I rammed it with earth, and plastered it with a preliminary lime coat to keep the soil in, which appears to have worked very well. I got lucky in that the top of the buck came within striking distance of the top tire course, requiring just a little modification to the tire height to make it level.
The Bond Beam:
My nephew Justin was down for the summer to help me with the bond beam. Getting the rebar spikes through the tire gaps was tricky at first but got much easier with experience. Getting the can walls going for the bond beam was a laughable failure at first, but we gradually developed a good technique and moved through half of it in about 4 hours. I was mixing the cement at this time by hand! One item you'll want to accomplish before you begin laying the can walls for the beam is to fill in the tire gaps on the top most tire course with adobe and let it dry thoroughly. This will provide a necessary bridge for the cans, which otherwise will sag and even collapse.
I planned for the loft space by embedding vigas partly into the bond beam. The ends were soaked in linseed oil to help prevent moisture damage, and they were shaved flat on one side to receive planks for the loft floor. This would eliminate the need to use standing supports that would interfere with what little space there was, as well as improve the aesthetics of the space and create a substantially more sturdy loft space, not to mention an attractive ceiling for the lower level.
When it came time to pour the cement, I brought out my mixer and borrowed my neighbor's generator. Unfortunately I did not have enough materials on hand and came short of pouring the whole beam in one day. I strategically left a gap where the rebar ends in the courses were not exposed and also amply embedded heavy nails and screws into the cement ends. I believe this worked very well
The Steel Mesh Dome:
Here is where my experience with art and sculpture really came in handy. I decided straight out that if I was going to build a dome, it was going to look like a dome, and not a teepee. I chose the straightest lengths of 1/2 inch rebar I could find and cut them to ensure identical length. I then pre-shaped them by tying one end to a bond beam spike and arching it around the circumference of the beam. With baling wire cut into handy lengths prepared at the first spike, I slowly and gently lifted the arched rebar into position, tieing it into place. If you lift too quickly, the far end of the rebar will bend down under it's own weight like a fishing pole hauling a Marlin, only it won't come back! This will leave you with an awkward angle close to where you're holding the bar. A few misshapen spots are ok though, since the rebar can be pulled and pushed where needed. This does require a bit of concentrated strength and balance however which comes only with practice and intuition.
With every major tweak, a walk away from the structure to get some perspective on the overall shape is necessary. It doesn't have to be perfect, because the shape can be refined during the plaster stage. It should have a nice balanced feel, if a touch irregular. One strategy I used to help me which differed from Earthship Biotecture's Hut Video, was to start by arching a set of two rebar parallel with each other along the east-west axis, and another set across the north-south, like two sets of railroad tracks crossing each other at a 90 degree angle. This makes the essential shape. Once you are satisfied with the way the arcs look from the four directions, tie them together at the square they form at the very top. This also makes a great opening for a skylight box, which I plan to install.
One Caveat: To get away with this you really need to plan so that you can position your receiving rebar spikes at the appropriate locations (2 in front, 2 in back, 2 on the east, 2 on the west, each set of rails spaced the same, all crossing over the center of the hut). This may also require strategically placing your tires.
Next. I attached a circular loop of rebar around the top portion of the criss-cross I made. This served as a connection for groups of partial arcs coming up from the beam. Because they can't go straight through the skylight box in the center, they simply stop at the rebar circle around it. Three of these partial arcs occupy each of the 4 remaining gaps. A second circular rebar loop was made as an anchor for the bottom and to add extra strength.
Doing it this way calls for fewer irregular overlaps of rebar, which can throw off the balance of the dome shape in a hurry. You just need to make sure you compensate by adding additional connections and supports to maintain it's form as you add the plaster.
Covering the Mesh Dome:
This was the biggest disappointment I encountered so far, primarily because I wrongfully envisioned it being like papier maché. Boy was I wrong! The fabric, for one, gets surprisingly heavy in the cement slurry, especially when you use heavier fabrics like denim, which I highly recommend for strength. For another, it doesn't adhere very easily to the wire mesh! It tends to slump down under its own weight, making it necessary to attach the bottom-most pieces of fabric to the cage with baling wire. This is not easy! You need to turn and twist the wire in a very concentrated way to get it to poke through the heavy fabric, and you can't be wearing heavy cement gloves to do it. So this was very tedious. That being said, I am anticipating that the higher layers will not require the extra effort, since they will enjoy a less steep arc to rest on.
I decided to work from the bottom up on purpose, just like laying overlapping shingles. I have no idea if there is any real added benefit from doing it this way. The cement plastering that will come later may simply meld it altogether into one cohesive whole, making the underlying layer order irrelevant. Still, you have to feel comfortable with your choices and techniques.
Miscellaneous:
The partial wall you see to the west of the hut is comprised of 2 wood palettes wrapped in chicken wire and rammed with earth. It was my hope that I could save some time by building a simple wall this way. The results are good enough for the storage shelter it will become a part of, but the amount of labor involved was more than I had anticipated. A perfect opportunity to use those earthbags!
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related images (click to view photos in full resolution)
The Hut Takes Shape
The Hut Finally Takes Shape
The hut started off using earthbags instead of tires The hut begins with earthbags.
Another band of earthbags Another band of earthbags.
The shaped hole The shaped hole. It's easy to see exactly where the layer of caliche started, about 4 feet down.
Earthbags abandoned for tires Earthbags abandoned for tires. The bags still come in handy as an alternative to cement for filling gaps.
Hut front without the bond beam and mesh dome. Hut front without the bond beam and mesh dome.
Tire wall view Tire wall view. Tire gaps partly filled with adobe.
Tire wall and door buck Tire wall and door buck.
Tires close up Tires close up.
Another close up, showing cut top. Another close up showing cut tire tops. The partial wall is made of palettes rammed with earth.
The bond beam and mesh dome The bond beam and mesh dome. My camera died so I never shot the bond beam progress.
Frontal view of the hut with mesh dome. Frontal view of the hut with mesh dome.
Another frontal view of the hut. Another frontal view of the hut.
View of the vigas and loft space. View of the vigas and loft space.
Mesh dome partly covered. Mesh dome partly covered.
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