[Cob] National Park Service earthbag construction

[mudhome at netzero.net]

At 09:24 PM 2/25/2004 -0500, Mary Hooper wrote:
>http://www.calearth.org/3vaults.htm
>
>the last photo on this page shows vaulted bags....right? but what's that odd
>looking white stuff on top of the bags?

I think that's a window in an earthbag endwall. There are other windows 
that shape visible way at the far end of the next vault (the vault that's 
offset to the left).

At 08:06 AM 2/26/2004 -0500, Patrick Newberry wrote:
>THe white stuff is snow. Cal earth is located in the high desert area of 
>California.

Snow, huh? I thought it was some kind of scratch coat... wasn't even sure 
it was white in real life after I clicked on it and peered at the larger 
version - camera flashes that close and/or bright sun can was wash things 
out pretty severly.

>Interesting enough, the building with the snow on the right, the covering 
>made from balls of stabilized earth made and placed one at a time. Of 
>course you can get a crew of people making the balls and it can go fast. 
>The reason for this was that Nader figured the cement often cracks due to 
>expansion and contration. Especially in the hot desert. The By using the 
>balls he is sort of predefining where the cracks will be. He then calks 
>the cracks with some type of lime mix I believe.

Yes, I also thought these blobs were supposed to be placed on shingle 
style. Let me see what Paulina Wojciechowska's book has to say...

"With the addition of some stabilizers the render applied to the domed or 
vaulted parts of the structure becomes more brittle, and cracks can occur 
through expansion and contraction with extreme temperature changes, as 
discussed above. This movement can be controlled through the fragmentation 
of the render mass. By placing the render in small "patties," a textured 
finish can provide thermal variation throughout the whole surface of the 
structure, creating air movement due to the temperature differential 
between the sun zone and shade zone within the render itself, never 
allowing the surface to overheat. As one side of a rounded patty heats up, 
the other cools down. This surface has been used for centuries in African 
villages and is prevalent in nature, for example in the scales of a fish or 
the trunks of trees.

Application
Once you have chosen the right stabilized mix (clay, lime, cement, etc.), 
apply a "scratch" coat to fill in large cavities and create the desired 
overall shape. Leave any irregularities in the surface so the second coat 
has somewhere to key into. To achieve the bubbly effect, patties of 
stabilized soil are placed like roof tiles, overlapping each other, 
starting at the base (like laying tiles) and working up the structure. 
Stagger the cracks so water will run down the grooves (see the photo on 
page 91)."

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or the publisher:
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from some people at The Hollies for 32.50 euros:
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amazon, etc....

Sarah