[Cob] Fwd: cob shake test info

Sun May 20 12:34:27 CDT 2012

Begin forwarded message:

> From: "dhowell at pickensprogressonline.com"  
> <dhowell at pickensprogressonline.com>
> Date: May 20, 2012 1:33:32 PM EDT
> To: Henry Raduazo <raduazo at cox.net>
> Subject: Re: [Cob] cob shake test info
>
> Ed,
> 	That is my primary concern also. I think it's common knowledge  
> that dirt leaches out iron. One thing I think is suspicious is that  
> bamboo has been tested to out perform steel rebar and it's a  
> fraction of the weight, yet there's never a mention of that. I  
> think bamboo dowels in cob walls (just laid across the wall and  
> cobbed around) would have the same function as steel rebar and  
> probably would keep the integrity of the wall.
> 	It's a good time for proposing such a thing because there is  
> almost no new construction and the inspectors may be more willing  
> to take the time to learn about cob just to have something to do. I  
> just can't scare the daylights out of them by proposing an American  
> style cob house. Although they look cool and are sufficient, they  
> look like a nightmare to an inspector that looks at straight lines  
> and 90 degree angles in homes all day.
> Damon
>
> On May 18, 2012, at 9:41 PM, Henry Raduazo wrote:
>
>> Damon:
>> 	You are of course absolutely right, and cob is vastly superior to  
>> adobe. That does not make it easy to get approval. Usually to get  
>> approval there is such a huge safety margin that the net effect is  
>> to be almost prohibitive to natural building.
>> 	People doing rammed earth structures used to put a little  
>> concrete in their mix just to make the inspectors feel happy.  
>> There was so little concrete in the mix and so much time between  
>> mixing and pouring the mix into the form that there was no  
>> strength imparted to the mix, but making inspectors feel good is  
>> important.
>> 	I have done it both ways. I had one project where the inspector  
>> required me go go in and get special approval for a wall, and my  
>> other projects have been the "Don't ask don't tell" format.  I  
>> have a huge respect for people like David Eisenberg who have  
>> devoted their lives to trying to get reasonable building codes  
>> that include natural building materials.
>> 	I have been through the whole college routine too with strength  
>> of materials and concrete design... I understand how engineers  
>> think, and I wish I had an answer to this problem other than just  
>> doing it under the table. I think the adobe got approved just  
>> because the prior situation was intellectually embarrassing.   
>> Native people could not build and finance traditional structures  
>> in their homeland, but they were allowed to build and finance  
>> structures built with imported materials and technology foreign to  
>> their native culture and traditions.
>>
>> 	I wonder: if we took apart some of the 1000 year old Pueblo  
>> structures and randomly tested some of the 1000 year old bricks,  
>> do you suppose that these bricks would pass current Adobe code? I  
>> don't think current adobe code has anything to do with a realistic  
>> assessment of what is required for a structure to last 1000 years.  
>> The strength that a wall has the day it is manufactured and the  
>> strength it has 100 or 1000 years from now depends on the chemical  
>> and mechanical stability of the materials. That is why putting  
>> steel in cob or adobe bothers me. It is not chemically stable and  
>> it expands as it reacts with moisture or minerals in the wall  
>> material. Think about all the possible impurities in clay soil.
>>
>> I wish Good Luck to the Alpha Testers,
>>
>> Ed
>>
>>
>>
>> On May 17, 2012, at 2:52 PM, dhowell at pickensprogressonline.com wrote:
>>
>>> Ed,
>>> 	Understood about quality control. I must point out concrete  
>>> mixes from scratch in a wheelbarrow can also have vastly  
>>> different strengths according to the amount of water used. Adobe  
>>> bricks? New Mexico Earthen Building Materials code states, "each  
>>> of the tests prescribed in this section shall be applied to  
>>> sample units selected at random at a ratio of five units per  
>>> twenty-five thousand bricks to be used or at the discretion of  
>>> the building official." Five out of 25,000 seems like a pretty  
>>> unrepresentative number for the whole. Quality control can be  
>>> done by performing tests at the foundation, sill height, and  
>>> lintel height of the walls. Did you know the adobe code allows a  
>>> psi of 250 and one out of five can have a psi less than that?  
>>> We're talking about the same material just a different building  
>>> procedure. Their code is a good guideline, but some things are  
>>> questionable, such as it requires concrete stucco which is an  
>>> accident waiting to happen according to the Devon Earth Building  
>>> Association. A healthy topic that must be discussed, don't you  
>>> think?
>>> Damon
>>>
>>> On May 17, 2012, at 2:09 PM, Henry Raduazo wrote:
>>>
>>>> 	The problem might be one of quality control. When you are  
>>>> mixing something in a large batching machine (like a concrete  
>>>> mixer) you have large 3-5 yard batches which are perfectly  
>>>> uniform. When you have small crews making 1/27th of a yard  
>>>> batches on a tarp asserting quality control is a nightmare.  
>>>> Every crew can not make every batch the same let alone getting  
>>>> the 5 or 6 different crews to make uniform batches.
>>>> 	I have been able to make uniform cob batches by mixing one ton  
>>>> batches on a concrete slab with a rototiller. That might satisfy  
>>>> a quality control person, but getting such anal persons to  
>>>> accept hundreds of batches made by half a dozen different crews  
>>>> might be expecting too much even if we had a code that described  
>>>> the material in a way to differentiate acceptable cob from  
>>>> unacceptable cob.
>>>>
>>>> Ed
>>>> On May 17, 2012, at 11:29 AM, dhowell at pickensprogressonline.com  
>>>> wrote:
>>>>
>>>>> Thanks Ron,
>>>>> 	As I mentioned; "but no paperwork which building officials  
>>>>> will accept."
>>>>>
>>>>>
>>>>> On May 16, 2012, at 8:17 PM, Henry Raduazo wrote:
>>>>>
>>>>>>> but no paperwork which building officials will accept.
>>>>>
>>>>
>>>
>>
>