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Cob: Re: cob,island foundation

Yun Que yunk88 at hotmail.com
Sun Feb 2 15:15:26 CST 2003


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<P>Cat here, the pounding was the only thing I was really describing, it's sort of hard without a picture to show you, but they pounded the stones in and used them as piers then built the stick frame on top, not a cob scenario.  A cob or any earth structure would need to be up on a burm or have a stone, brick, block knee wall to keep the moisture from wicking.  </P></DIV>
<P>I have an old black smith forge on my farm that was built on the ground with 10" x 10" timbers laid into the dirt, it is over 75 years old and the timbers are still solid and holding.  The reason is that the builder piled a bunch of stone around and filled it with earth creating an island of dirt above the ground and then set the timbers and the building.  The roof was extended far enough out to cause the water to fall beyond the island and a shallow  trench at the back hill moves all the hill drainage around the foundation island.  It has an earth floor that is bone dry all times a year and a small brick fire place that is a little tilty but I think it has more to do with the amount of moonshine in the construction crew then the stability of the foundation! What I don't understand is why the termites have not eaten it?  Unless they treated the timbers in some way that I can not see or smell.  A good ol boy told me that  they soaked timbers in some kind of salt brine to preserve them in the old days, but one hears many of these stories in these parts with a lot of info missing , usually because they were little ones when this was going on and the memory is fragmented.  Anyone know?<BR><BR>for the good of all</P></DIV>
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<DIV></DIV>>From: "Frances Grill" <GRILL at VTC.NET>
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<DIV></DIV>>Reply-To: "Frances Grill" <GRILL at VTC.NET>
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<DIV></DIV>>To: "Yun Que" <YUNK88 at HOTMAIL.COM>,<CHANSEY at EARTHLINK.NET>,<COBLIST at DEATECH.COM> 
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<DIV></DIV>>Subject: Re: Cob: Re: cob, pise 
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<DIV></DIV>>Date: Sat, 1 Feb 2003 08:40:03 -0500 
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<DIV></DIV>>Cat, Do you know how they got the foundation above the dirt level? It seems (at least in conventional construction anyway) that one reason for the footer is to get the side walls up away from the damp earth so you cicumvent wicking the moisture up into the sidewall. It seems that would be even more important with soil construction. So if the rocks are driven into the earth how do you prevent wicking ? Maybe it was only used for floors??? which sounds workable being inside.? PAZ, Pedro 
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<DIV></DIV>> -----Original Message----- 
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<DIV></DIV>> From: Yun Que <YUNK88 at HOTMAIL.COM>
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<DIV></DIV>> To: chansey at earthlink.net <CHANSEY at EARTHLINK.NET>; coblist at deatech.com <COBLIST at DEATECH.COM>
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<DIV></DIV>> Date: Friday, January 31, 2003 11:01 PM 
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<DIV></DIV>> Subject: Re: Cob: Re: cob, pise 
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<DIV></DIV>> > but the stones for the foundations were pounded into the ground this way and no other foundation was needed. They did not dig a hole first! The house was then set on these piers. Thinking I may do my floor this way, but it may work for rammed earth if the forms are well buttressed. 
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<DIV></DIV>> for the good of all Cat 
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<DIV></DIV>> >From: "SANCO Enterprises, LLC" 
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<DIV></DIV>> >Reply-To: "SANCO Enterprises, LLC" 
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<DIV></DIV>> >To: "Jill hotmail" ,"cob list" 
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<DIV></DIV>> >Subject: Cob: Re: cob, pise 
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<DIV></DIV>> >Date: Fri, 31 Jan 2003 19:38:35 -0700 
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<DIV></DIV>> >Jill inquired, 
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<DIV></DIV>> >Jill made a serious inquiry about the different methods of construction and I will attempt to clear up a few things. I realize that those of us who have been around for a while take things too lightly--and if I have I apologize. 
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<DIV></DIV>> >Let's start with some basics. All earthen compositions regardless of the terminology must accomplish one thing ---provide a strong building component. If you look at the material ratios of clay, soil, sand or aggregate for cob, adobe or rammed earth, they are all essentially the same when used in their natural state. 
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<DIV></DIV>> >Straw is an added component that that has to be used appropriately. When used in cob or in more humid climates, the permeability of the structure in improved through the use of straw--it breathes better. In less humid areas where rain fall is not a factor, you can do without the straw. In many areas where there is not a sufficient amount of non-clay material, straw, grass or other organic materials will be used to minimize cracking and provide for a monolithic unit. 
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<DIV></DIV>> >Pise and Rammeed Earth 
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<DIV></DIV>> >NO-EQUIPMENT: if this is the approach one is going to take, the forms can be simple. Hand tamps do not provide the same amount of impact force as pneumatic equipment, therefore the lifts must be in the 2 or 3 inch range. Any more than that, you will have weak or void areas when the forms are pulled. The moisture content is critical and should be optimum based on the materials being used. With hand tamps you will be fortunate if you achieve 90% compaction. This would be identical to the material mix for CEB's (compressed earth blocks) made by machine. Pozzolan based materials or cement may be added to the base material to add strength. This is a matter of choice. If enough cement is used, you will not need a render or plaster. 
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<DIV></DIV>> >Machinery and equipment for Pise and Rammed Earth 
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<DIV></DIV>> >Tampers (powder-puff), usually about 6" in diameter is used to tamp the material. It is similar to a pogo-stick with a plate of steel at the end and is run by compressed air. Bobcats, tractors and conveyors are often used to deposit material into the forms. Here the lifts can be 6" deep as the tamper is capable of achieving 100% compaction. Over-compacting can blow-out a form. Cement is optional and will achieve the same results as above. 
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<DIV></DIV>> >Easton's Method for PISE 
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<DIV></DIV>> >This is not rammed earth or Pise--it is concrete, be it a weak mix, that is applied. It is no different than the methods used for guniting a swimming pool, lining a mine shaft or stabilizing a hillside. It is the same equipment and process used for ferro-cement applications. You can not achieve consolidation and compaction of soil and optimum moisture simply by blowing or guniting the material---it will fall apart. Eaton's use of a high cement content is what makes his process work. I works and is successful--but expensive. 
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<DIV></DIV>> >All earthen construction has limits as to how high you can build. The aspect ratio is the limiting factor. This is another topic onto its own. 
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<DIV></DIV>> >Re-bar or reinforcing steel will work only if can be encapsulated to utilize its properties. It has very little beneficial use in cob, adobe or CEB construction. When used in a rammed earth or a-la-Easton process, you enrich the material around the re-bar with cement to create a beam or column. 
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<DIV></DIV>> >Hope this has helped a wee bit. 
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<DIV></DIV>> >SANCO Enterprises, LLC 
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<DIV></DIV>> >Paul Salas, General Manager 
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<DIV></DIV>> >P.O. Box 45741 
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<DIV></DIV>> >Rio Rancho, NM 87174 
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<DIV></DIV>> >(505) 238-1485 
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<DIV></DIV>> >chansey at earthlink.net 
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