Cob: RE: RE: small cob housing

Thu Jul 3 18:04:18 CDT 2003

Well,

A lot of this has to do with your climate and your mix.  Our cob dries well
within a few days, and even in a form, in dries withina week or so.  We add
a little portland cement to help the curing process, and that helps to
create a stronger mix when wet as well.

Abe
-----Original Message-----
From: owner-coblist at deatech.com [mailto:owner-coblist at deatech.com]On Behalf
Of Joe Skeesick
Sent: Thursday, July 03, 2003 5:29 PM
To: coblist at deatech.com
Subject: Cob: RE: small cob housing

Some people have tried cement mixers to mix cob but the standard drum style
mixer just isnt a good tool for the job and you end up being able to mix
cob with your feet faster. A mortar mixer works much better but still ends
up with a wet mix and the straw has to be mixed in manually or it fouls the
blades. Basically what you need to do to mix large amount of cob is to
replicate the trodding action of foot mixing.

Traditionally cob was made in an animal lot over time, allowing animals cows
and or horses to trod over an area for months pressing the elements together
like kneading dough. We now try to replicate this with our own feet and a
tarp. It takes a lot of work to make relatively small batches. The best way
to mimic this process with machines is quite simply replacing horse hooves
with horsepower. This is often done with a tractor (hence called tractor
cob). Ive found personally that the very best small-scale cob mixing unit
is a bobcat. The bobcat because of its counter rotating wheel steering can
simply spin in place around the clay/sand/straw mix, churning it squishing
it together under the weight of the unit. The added benefit of the front end
loader on the bobcat to both scoop the mix back into a pile and then deliver
it within reach of folks working on an elevated wall section make it a great
tool to have. It also fits well in a tight building site. You can of course
use a standard tractor or even a truck but they both have drawbacks (the
truck in particular) The important aspect of mixing cob though is that the
individual elements have to be compressed together to get everything to bind
well. Tumble mixing will never get you a really well bonded mix. Save the
cement mixer for the lime plaster. It works great for that.

On the topic of pouring cob
 well, its not really cob at that point. Cob
takes quite some time to dry out and if you had a mix that was wet enough to
pour and you trapped it inside forms Im afraid it would take months to dry
enough to support its own weight to allow the forms to be removed. Im
guessing here since Ive no experience at all in that area. When I discussed
building cob relatively quickly please note the relatively aspect. There
is still a drying time that is needed for each lift to be able to support
more cob above without schlumping J (basically collapsing under the weight
of new cob above it). Still, even with that drying time, the home I spoke of
built by Kevin McCabe took only 3 months to build the walls on a 3200
square foot home. The entire project took 15 months with him and 2 other
workers on the job. The home was built to a high level of finish as it was
originally built with immediate resale in mind. (he and his wife changed
their minds once it was built and moved in instead). That is the sort of
relative quickly construction I was referring to.

Best of luck with your project however you decide to build it.

Joe

-----Original Message-----
From: owner-coblist at deatech.com [mailto:owner-coblist at deatech.com]On Behalf
Of Mary Hooper
Sent: Thursday, July 03, 2003 10:15 PM
To: coblist at deatech.com
Subject: Cob: small cob housing

Now I'm going to try to send this message to the list instead of just the
one person who brought it up!!!

snip snip snip:::
Cob buildings can be large, they can be made with large machinery and
theycan be made relatively quickly. However, it is also a human scale
technologythat can be made almost completely by hand with simple tools and
.... ::end snip

Now, there's a thought I had not had.... using large machinery.... has
anyone used a cement mixer instead of feet to mix the mud????
I imagine a big truck size mixer and the construction guy saying "You want
me to mix WHAT in it?" and the forms people saying "You want to me to pour
WHAT in my forms?"
Anyone have any wisdom to impart for either sitution? Would a large poured
wall dry without cracking? Would those of us who have tricky knees and
reduced energy levels benefit from thinking "outside the box" on this? Not
to go fully industrial strength, but how could we utilize modern equipment
to make the job easier on our old joints and/or speed up the work?
Mary in NC

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<DIV><FONT face=Arial color=#0000ff size=2><SPAN 
class=350475722-03072003>Well,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN 
class=350475722-03072003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=350475722-03072003>A lot 
of this has to do with your climate and your mix.  Our cob dries well 
within a few days, and even in a form, in dries withina week or so.  We add 
a little portland cement to help the curing process, and that helps to create a 
stronger mix when wet as well.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN 
class=350475722-03072003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN 
class=350475722-03072003>Abe</SPAN></FONT></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma 
size=2>-----Original Message-----<BR><B>From:</B> owner-coblist at deatech.com 
[mailto:owner-coblist at deatech.com]<B>On Behalf Of </B>Joe 
Skeesick<BR><B>Sent:</B> Thursday, July 03, 2003 5:29 PM<BR><B>To:</B> 
coblist at deatech.com<BR><B>Subject:</B> Cob: RE: small cob 
housing<BR><BR></FONT></DIV>
<DIV class=Section1>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt">Some 
people have tried cement mixers to mix cob but the standard drum style mixer 
just isnt a good tool for the job and you end up being able to mix cob with 
your feet faster. A mortar mixer works much better but still ends up with a 
wet mix and the straw has to be mixed in manually or it fouls the blades. 
Basically what you need to do to mix large amount of cob is to replicate the 
trodding action of foot mixing.<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt"><![if !supportEmptyParas]><![endif]> <o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt">Traditionally 
cob was made in an animal lot over time, allowing animals cows and or horses to 
trod over an area for months pressing the elements together like kneading dough. 
We now try to replicate this with our own feet and a tarp. It takes a lot of 
work to make relatively small batches. The best way to mimic this process with 
machines is quite simply replacing horse hooves with horsepower. This is often 
done with a tractor (hence called tractor cob). Ive found personally that the 
very best small-scale cob mixing unit is a bobcat. The bobcat because of its 
counter rotating wheel steering can simply spin in place around the 
clay/sand/straw mix, churning it squishing it together under the weight of the 
unit. The added benefit of the front end loader on the bobcat to both scoop the 
mix back into a pile and then deliver it within reach of folks working on an 
elevated wall section make it a great tool to have. It also fits well in a tight 
building site. You can of course use a standard tractor or even a truck but they 
both have drawbacks (the truck in particular) The important aspect of mixing cob 
though is that the individual elements have to be compressed together to get 
everything to bind well. Tumble mixing will never get you a really well bonded 
mix. Save the cement mixer for the lime plaster. It works great for 
that.<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt"><![if !supportEmptyParas]><![endif]> <o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt">On the 
topic of pouring cob
 well, its not really cob at that point. Cob takes quite 
some time to dry out and if you had a mix that was wet enough to pour and you 
trapped it inside forms Im afraid it would take months to dry enough to support 
its own weight to allow the forms to be removed. Im guessing here since Ive no 
experience at all in that area. When I discussed building cob relatively 
quickly please note the relatively aspect. There is still a drying time that 
is needed for each lift to be able to support more cob above without 
schlumping </SPAN></FONT></SPAN><SPAN class=EmailStyle15><FONT face=Wingdings 
color=navy size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Wingdings; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: Arial; mso-hansi-font-family: Arial; mso-char-type: symbol; mso-symbol-font-family: Wingdings"><SPAN 
style="mso-char-type: symbol; mso-symbol-font-family: Wingdings">J</SPAN></SPAN></FONT></SPAN><SPAN 
class=EmailStyle15><FONT face=Arial color=navy size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt"> 
(basically collapsing under the weight of new cob above it). Still, even with 
that drying time, the home I spoke of built by Kevin McCabe took only 3 months 
to build the walls on a 3200 square foot home. The entire project took 15 months 
with him and 2 other workers on the job. The home was built to a high level of 
finish as it was originally built with immediate resale in mind. (he and his 
wife changed their minds once it was built and moved in instead). That is the 
sort of relative quickly construction I was referring 
to.<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt"><![if !supportEmptyParas]><![endif]> <o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt">Best of 
luck with your project however you decide to build it. 
<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
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<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
size=2><SPAN 
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; mso-bidi-font-size: 12.0pt">Joe<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal><SPAN class=EmailStyle15><FONT face=Arial color=navy 
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<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face=Tahoma color=black 
size=2><SPAN 
style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Tahoma">-----Original 
Message-----<BR><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> 
owner-coblist at deatech.com [mailto:owner-coblist at deatech.com]<B><SPAN 
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Mary Hooper<BR><B><SPAN 
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Thursday, July 03, 2003 10:15 
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> 
coblist at deatech.com<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> 
Cob: small cob housing</SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face="Times New Roman" 
size=3><SPAN 
style="FONT-SIZE: 12pt"><![if !supportEmptyParas]><![endif]> <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face="Times New Roman" 
color=black size=3><SPAN 
style="FONT-SIZE: 12pt; COLOR: black"> </SPAN></FONT><FONT 
color=black><SPAN 
style="COLOR: black; mso-color-alt: windowtext"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face=Arial color=black 
size=2><SPAN style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Arial">Now I'm 
going to try to send this message to the list instead of just the one person who 
brought it up!!! </SPAN></FONT><FONT color=black><SPAN 
style="COLOR: black; mso-color-alt: windowtext"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face="Times New Roman" 
color=black size=3><SPAN style="FONT-SIZE: 12pt; COLOR: black">snip snip 
snip:::<BR>Cob buildings can be large, they can be made with large machinery 
and<BR>theycan be made relatively quickly. However, it is also a human 
scale<BR>technologythat can be made almost completely by hand with simple tools 
and<BR>.... ::end snip<BR><BR>Now, there's a thought I had not had.... using 
large machinery.... has<BR>anyone used a cement mixer instead of feet to mix the 
mud????<BR>I imagine a big truck size mixer and the construction guy saying "You 
want<BR>me to mix WHAT in it?" and the forms people saying "You want to me to 
pour<BR>WHAT in my forms?"<BR>Anyone have any wisdom to impart for either 
sitution? Would a large poured<BR>wall dry without cracking? Would those of us 
who have tricky knees and<BR>reduced energy levels benefit from thinking 
"outside the box" on this? Not<BR>to go fully industrial strength, but how could 
we utilize modern equipment<BR>to make the job easier on our old joints and/or 
speed up the work?<BR>Mary in NC</SPAN></FONT><FONT color=black><SPAN 
style="COLOR: black; mso-color-alt: windowtext"><o:p></o:p></SPAN></FONT></P></DIV></BODY></HTML>

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