Based on that and subsequent input, here's a sketch of the side view of the design I'm presently favoring.
The earth bag walls go straight up with periodic buttresses along the horizontal length. At 8 feet up will be the floor joists, then the straight earth bag walls will end up another two feet. At that point will start the 10-foot radius concrete dome, which will have insulation around it. So the parabolic, catenary arch has been nixed. We're still sticking with the slight arch as the house goes east and west, concave to the north to help the house resist the backfill. Torg also recommended having anchors out in the back-fill, tied to the earth bag wall. The east and west ends of the house will still be rounded. Torg pointed out that having the north wall convex to the backfill would tend to wall failure, whereas having the north side concave to the backfill would tend to the earth packing the wall tighter -- the arch principle.
Torg suggested that I not use any cement in the earth bags, saying that cement will crack in the event of an earthquake or settling, whereas rammed earth in the earth bags will just “reanneal”.
Regarding most of our building time being through the winder, per the 180-days provided by the 1031 roll-over, John Day suggested that I use a "high tunnel" cover over the site. This could entail using pvc pipe with plastic overlaid, and some kind of heater inside, e.g. propane, augmented with a rocket stove. This would enable us to build through freezing temperatures outside.
I'm wondering if this is a plausible approach. How much PVC pipe and plastic will that require; and how hard will that temporary shelter be to build? How much energy will it take to heat to prevent freezing?
Another question I have regards storage. What would be the best way to store my building supplies and other things while we are building?
Torg said that even with the compact earth, not using cement, we would want to keep the structure above freezing so that the wetted earth can properly dry.
In addition to his other skills, Torg also is an architect (not presently licensed in Utah). He said he could draw up our plans, including the electrical, plumbing (including rainwater capture, cisterns, and compost tank for the main restroom), and engineering aspects; and he has an associate who is a licensed Engineer in Utah, who could then sign off on the plans.
I'll need to decide what appliances and how many will be AC versus DC for each room, to determine how many lines to run to that room. In earth bag construction, the wiring and plumbing is laid down as you go. You don't want to run conduit, because the metal tends to bend from the compacting process.
One of the things the community is talking about getting right away is a track hoe for excavation, road building, back filling etc. By the time we rent a track hoe for the various homes we want to build on the site, we will have paid for the track hoe; and we can get our money back out of the track hoe when we're done.
That sounds nice, except that up front we are strapped for cash, so I would rather rent at first. Aaron N. knows two people with track hoes.
2 comments:
Hi Sterling
Just noticed your project very cool.
I would suggest electrical conduit instead of PVC as the frame for your "high tunnel" as you call it. PVC is to flexible and prone to falling down easier because of it and hard to work with when making this kind of structure.
The reason I know this is because I built some similar frames to cover my fruit trees with netting to protect from the birds and used PVC at first and it was much tougher to work with then I anticipated because of the flexibility when using those kinds of spans. Electrical conduit was not much more expensive and worked much better. It can then be recycled for the house electrical and also for garden vine frames or even green or hot house frames etc.
Blayne
I would also be very leary of using earthbag butted up against the soil or backfilled. I built retaining walls for over twenty years and I see nothing in earth bag construction that would give me any confidence it has the kind of support needed to retain the earth properly even using extroverted arch.
I personally would use common concrete block. with rebar reinforcing and grouted solid. In fact i an designing such a structure and it is likley comparable in price to an earth bag structure.
You can find the bloc pretty cheap by placing ads on craigs list. You can dry stack it and use fiber cement to bond it, but you'd need a mason to do the first course to get it nice and level for the dry stack which you can do yourself. You could probably find a mason pretty reasonable to do the first course either on craigs list or if any job sites around where some are working go and ask the block layers if they do side jobs. Not the contractor but the block layers themselves.
Email me if you want more info.
Also curious why you abandoned the catenary dome idea? It would seem to be more practical for snow loads.
Blayne
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