In the most recent corresdence (near the top), Owen's comments, received the morning after I posted this, are indicated in red.
After writing the below, I bumped into the Owen-Torg correspondence regarding Nubian technique for building Catenary arches using stabilized earth blocks.
I found the following page http://www.earth-auroville.com/index.php?nav=menu&pg=earthauroville&id1=4 which has a lot of photos that resemble the paramecium plan we're contemplating.
In particular, here's a photo of the Earth Institute which has a fair resemblance to what our finished home might look like.
except ours would be made of earth bags and would not be straight but curved along its length/ and ours would not have square walls on the exterior, and the ends of our vault would be rounded like a half-beehive.
Perhaps we could use the ends as the Nubian form and move forward from there first.
Compressed earth block (CEB) vaults: These vaults require skilled, experienced masons. It's not something you can learn overnight. Building CEB vaults on a curved house would be very tricky. Plus, they are better suited to mild climates. You want an insulated roof for Utah. Note: the current design lacks adequate space for insulation.
Instead of CEB vaults, I recommend ferro-cement or nylon cement vaults with about R-40 insulation: http://www.angelfire.com/in2/manythings/TEXT/NYLON-CEMENT.htm (tech info near bottom of article) This makes it relatively simple to add dormer vaults, eyebrows over windows, curved end walls, etc. using almost any curve you want. At this point, this looks like the best 2nd story system for you.
Make a 6" reinforced concrete bond beam for floor joitss to sit on. Embed upright sections of rebar for the vault.
It's best to make rebar trusses: http://www.earthbagbuilding.com/projects/shop.htm (see last 3 photos)
Bend the rebar around a jig so they're all the same size and shape. Then tie these long, curved trusses to the short pieces in your bond beam. Then add perpendicular rebar and mesh.
Here are some interesting scaffolding pictures (no forms, just guides [possible with brick]):
And here's a couple of photos demonstrating the strength of the catenary arch.
===============
Hi Owen,
Yes, I would appreciate a summary of recommendations.
Okay, let's decide on the basic building system first.
We plan on using a ~10% concrete mix in our external bags and that they will be hardening as we go up, no more than two or three courses in a day.
Would you agree that with 10% concrete mix, that the first eight feet, which barely tip inward, will be strong enough to support the beams for the solarium roof/deck and the second floor?
Yes, no problem.
How far apart should these beams be? How big (e.g. minimum) should they be? Will they need any reinforcement?
I think you're referring to floor joists. These are typically TJI joists set 16" apart. You can go 20' span with certain brands/models of 12" of TJIs. Are you still planning a block or CEB wall down the length of the house? This means you could use 10" TJIs and would eliminate the awkward flex in 20' spans.
I've got a question. Will the bags need to be protected from rain, once they are in place, before they are sprayed and finished on the exterior?
Yes. You'll need to protect them from sunlight with tarps until you can get a coat of plaster on, even though rain is not a big concern (because they're stabilized). That's why I recommended spraying gunnite in stages. You don't want lots of tarps flapping around for months.
We were planning on 20-inch bags from Cal-Earth for the vault. Will that be thick enough, or should we use thicker bags. Does Cal-Earth make anything thicker than 20 inches?
Not sure what sizes they have. 20" is a good size.
I'm thinking that going up 8 feet that we'll be pretty much okay without much reinforcement, form-wise, for the first floor. Then maybe we could go ahead and install the second floor to stand on and put forms on for going up higher from there on the exterior walls.
That sounds good. We just need to work out the details on the 2nd story forms and building method.
What do you think about Tim's suggestion to build the interior walls as we go up, to help support the exterior walls?
Yes. This is a good way. You can overlap the corners so they interlock.
Sterling
----- Original Message -----
From: Owen Geiger
To: Sterling D. Allan
Sent: Thursday, November 19, 2009 6:15 PM
Hi Sterling,
It all depends on the details: distance between supporting walls, what the supporting walls are made of (earthbag?), slope/shape of parabola, stabilized or unstabilized soil, how many guides, how strong the guides are, etc.
It sounds like a lot of guesswork to me. You could get up to 8 feet high and suddenly the walls start to lean and sag between support walls. And then what do you do? You'd have to tear everything apart and start over. It doesn't sound like a good plan to me.
Khalili is the only one who's done this, and he used forms throughout. And Kelly thinks he used earthbags only so far up and then poured concrete on top. The vaulted school in the Philippines used concrete on top, too. http://www.earthbagbuilding.com/projects/school.htm
Kelly Hart's elliptical dome collapsed, and the Om Dome (world's largest earthbag dome) started to lean in and had to be rebuilt. These were built by talented people, but they misjudged what can happen with tons of weight teetering in the air.
http://www.earthbagbuilding.com/projects/omdome.htm
So I still think it's possible, but all the details have to be worked out very carefully. And I don't know anyone who can give you 100% assurance on this -- not me or anyone else, because it hasn't been done before.
I can write a summary of recommendations if you'd like.
Owen
--- On Thu, 11/19/09, Sterling D. Allan
[...]:
----- Original Message -----
From: "Tim Hall"
To: "Sterling D. Allan"
Sent: Wednesday, November 18, 2009 10:03 PM
Subject: Re: 180 days over end of April; Re: Parabolic Arch better; change convex to the south
Aloha Sterling,
As far as building forms we are going to build interior walls that
will hold wall roof in place, you have at least four walls from front
to rear. we only go no more than three rows of bags per day if we are
lucky. we only need guides .
Aloha Tim
----- Original Message -----
From: Owen Geiger
To: Sterling D. Allan
Sent: Wednesday, November 18, 2009 5:16 PM
Subject: Re: 180 days over end of April; Re: Parabolic Arch better; change convex to the south
Hi Stirling,
Just to restate the essentials, you definitely need a form, and it must be very strong. You'll have tons of weight overhead. And yes, do it in sections about 4-8' long and slide the form along.
Here's Kelly Hart's advice on vaults: www.earthbagbuilding.com/faqs/shape.htm#vaults
He cautions against going over 8' wide! I'm convinced you can go much larger, but again, you have to be very careful. It may seem simple in principle until you're right in the middle of it. (Sort of like mountain climbing, where you tell yourself "just keep climbing." But you eventually reach a point where you're in over your head.)
Domes lean into themselves, so they're very stable. Vaults have nothing to lean on and will just suddenly fall over. And, of course, they won't care if someone is standing underneath.
Again, no one has done what you're attempting [...]. Please do more research and, even better, build a demo vault.
Concrete block: Sure, this is an option, but it looks ugly and has huge environmental cost. Anything with high thermal mass will work. Why not introduce something that's natural and beautiful. Ex: you'll never tire of looking at natural patterns/textures created by adobe, pressed earth block or stone.
Owen
--- On Wed, 11/18/09, Sterling D. Allan
From: Sterling D. Allan
Subject: Re: 180 days over end of April; Re: Parabolic Arch better; change convex to the south
To: "Owen Geiger"
Date: Wednesday, November 18, 2009, 2:26 PM
Hi Owen & Tim & SHV people,
Now that the reality of the 180-day thing has set in, and I'm adjusted to the idea that I'll have to purchase my supplies first and store them, then build, I'm not quite so stressed about being under the gun to finish the house so soon.
We'll have some community funds (hopefully) that I can draw from toward repaying the money I'll be paying up front for the community land.
So back to the questions regarding the Paramecium house design.
I can see how a wall in its earlier stages would not need to be supported, but the steeper the angle goes toward the top, the more the bags are going to want to slough off, and the more the walls are going to want to tip over -- until they meet at the top where they can lean into one another.
I'm wondering how much and how I'll need to provide forms against which the rising walls can lean.
I can see how the bags would not slough off in a beehive shape structure -- I've built several snow forts that way -- but I don't see how the bags would not slough of near the top of the vault construction.
One way to do this would be to complete the arch on one end, over a form, then move that form forward, and complete another arch section. That would prevent longer sections of bag and longer sections of barbed wire; and it would require barbed wire lengths to protrude from the unfinished courses, to tie in to the next section. If these hung down into the inside, then they wouldn't get in the way of spraying the exterior in stages to protect the bags from UV deterioration; and it would enable tarp to cover the unfinished portions without getting shredded by the barbed wire.
Another way to do it would be to build a stick framework over which to build the vault; but that would take a lot of wood. Perhaps I could gather scrap wood from a dilapidated barn or something, then use that as firewood when I'm done.
Either way, I'm wondering how frequent the support needs to be. Maybe as I go up, I could have sheets of plywood that I set in place during the tamping down of the bags, then I can pull those out and move them up for the next course. I would think that after tamping, the slough tendency would be gone, except near the very top. Also, I'm wondering about how much leeway we have in the smoothness of the interior and exterior surfaces. If the plywood is overlapping, so there is a 1/2 - 3/4 inch line, can that be covered by the chink-fill stage? Or is it best to avoid that?
Also, regarding the vertical wall through the middle of the arch in the West end of the home, I would think it would be easier to just make that out of cinderblock. I'm open to using conventional materials in some places. This home will be a hybrid of old, new, future technologies.
Your thoughts?
Sterling
----- Original Message -----
From: Sterling D. Allan
To: Owen Geiger ; Tim Hall ; Safe Haven Villages admin egroup
Sent: Monday, November 16, 2009 8:14 AM
Subject: 180 days over end of April; Re: Parabolic Arch better; change convex to the south
Hi Owen,
Thanks for the input.
When you suggest a wood form for the vault during construction, maybe you can elaborate what that would entail. How frequent would the support need to be? Are you talking a form that would fill the entire interior during construction, or one that would be moved along, completing from one end to the other (using rice bags rather than long length tubes from Cal-Earth)?
As for spraying the walls as we go, what kind of company am I looking for? You're not talking shotcrete are you?
As for the middle, straight wall, isn't the compressed earth block (CEB) similar to concrete forms except that with concrete you get to have anchors between the forms which you later break off the ends that protrude from the concrete. Wouldn't that be a herculean challenge to create a form that tall and wide with no anchor between. I've not studied the earth CEB method.
The thing that has me most nervous about all this is the very shore time we have to work. I had thought that we had 45 days from closing to identify a property, then 180 days after that to finish spending the money for the 1031 exchange. However, Susan informs me that we have 180 days from closing (Oct. 30) to spend the money; which means we have until the end of April; and in Utah, early April is still hits intermittent freezing; so with building season starting with a few days in March, we would barely have a month of time to launch this Earth Bag construction. During the freezing season we could do the permitting, well-digging (if we go that route), excavation, doorway and window form building, form building.
I'm just not comfortable with the idea of buying everything before building and hoping we have enough, and not having those funds to draw on for the labor help we'll need.
And we're attempting a scale that pushes the envelope for this type of construction which even in its more tried form has but barely penetrated into Utah. The bureaucratic hoops could be daunting as well.
The learning curve for me is huge too. I'm venturing into all kinds of unknown territory:
- earthbag is new to me as of 1.5 months ago
- rainwater capture: I haven't yet looked into the particulars
- bottle/can walls: I haven't yet looked into the particulars
- earth floor: barely know about it
- earth bag plumbing and electricity: barely know about it
- earth home insulation and waterproofing: barely know
I should have my head fully wrapped around these things in order to properly design the home, which is one of the first things that needs to be done.
I can't help but think that we're not being realistic. We're trying to do too much in too short a period of time.
I'm thinking it might be best to shift to something less exotic.
Sterling
----- Original Message -----
From: Owen Geiger
To: Sterling D. Allan
Sent: Monday, November 16, 2009 2:09 AM
Subject: Re: Parabolic Arch better; change convex to the south
Hi Sterling,
I thought you were going to use a wood form to build the vault. Now it sounds like you're going to use a rope guide to line up each course. You definitely need a wood form or the walls will fall over during construction. Vaults are very tricky, even small ones. You're attempting to build possibly the largest earthbag vault in the world... use extreme caution.
Interior 12" wall: Narrow earthbag walls are not very stable during construction. I recommend adobe or compressed earth block (CEB) for this wall. This will also produce a straighter, nicer looking wall that won't need plaster.
Curving the house toward the sun is the best, I agree.
Also, create extra room at the top of the stairs, in the bathtub, etc. People need adequate space to feel comfortable.
I'd start looking for a company who can spray the earthbag walls. This will greatly speed things up. The best way is to spray the exterior in stages so you don't have to keep everything tarped. (Tarps want to blow away in the wind.)
Owen
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