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Cob: Re: Posts embedded in cob

Shawn Honeychurch ironfire at cyberlink.bc.ca
Wed Nov 1 06:03:20 CST 2000 

RE: Posts embedded in cobHi Will
Thanks for your thoughts.  We really want to go with the post and beam design, because it will be easier for us to get a building permit.  With your staw-clay idea, how dense would you pack it into the forms, do you think?  And could we still cob over the posts?  Would cob on a straight straw-clay be any stronger than a straight cob wall?  I worry about it wanting to fall over, being lighter weight and all.  The idea of building faster and improved insulation value with this method is, of course, appealing, but do you think there is a greater risk of having bug problems in a straw-clay wall than a cob wall?  

I am not inclined to building with straw bales as I have heard too many stories of problems with bugs and rot.  Am I being paranoid as we live in a semi-arid climate here?

Thanks for your input.
Robynn

  ----- Original Message ----- 
  From: Firstbrook, Will 
  To: 'Shawn Honeychurch' ; coblist at deatech.com 
  Sent: Wednesday, November 01, 2000 11:19 AM
  Subject: RE: Posts embedded in cob


  Hi Shawn and Robynn, 

  The cob as it shrinks/dies will separate from the embedded posts. Which might not be a problem if the wall is quite thick surrounding the posts. If the cob is thin around the post it will crack. Also since you intend to have straight walls with the post in the corners the wall will be weak in the corners. The strength of cob would be compromised in that design. Not a good idea in an earthquake zone. Note that straight walls are considerably weaker than curved walls. One of the things I love about cob is the organic curved walls.

  Some options you might want to consider: 

  Make the cob loadbearing, build temporary posts holding the roof then build the cob walls put a top plate on and lower the roof onto the cob. Curve the corners for greater strength.

  Leichlehmbau (often refered to as light clay or straw-clay). Using your current ideas make temporary forms for the walls and pack straw dipped into a clay slip into the forms, once the walls have hardened remove the forms and plaster both sides of the wall with cob plasters. The advantages of this technique are much improved insulation value, faster construction time & lighter walls. You can put lots of cob on the inside of the wall to provide mass.

  Load bearing or modified post and beam strawbale construction can easily give straight walls and strong corners. 

  Regards, 
  Will 





  -----Original Message----- 
  From: Shawn Honeychurch [mailto:ironfire at cyberlink.bc.ca] 
  Sent: Tuesday, October 31, 2000 7:06 AM 
  To: coblist at deatech.com 
  Subject: Cob: Posts embedded in cob 



  Hi All; 

  We are planning to build a post and beam style house with cob walls.  We are 
  going to build short sections of straight cobs walls between the posts using 
  forms and shape the cob around the posts so that the finished house will not 
  have any posts showing.  We were just reading in the "Cob Builders Handbook" 
  that this is not suggested due to the shrinkage of the cob while it is 
  drying. 
  Has anyone tried this, or does anyone have suggestions on how to get around 
  this problem so we don't have to totally redesign the house? 

  Shawn and Robynn 

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<HTML><HEAD><TITLE>RE: Posts embedded in cob</TITLE>
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<DIV><FONT face=Arial size=2>Hi Will</FONT></DIV>
<DIV><FONT face=Arial size=2>Thanks for your thoughts.  We really want to 
go with the post and beam design, because it will be easier for us to get a 
building permit.  With your staw-clay idea, how dense would you pack 
it into the forms, do you think?  And could we still cob over the 
posts?  Would cob on a straight straw-clay be any stronger than a straight 
cob wall?  I worry about it wanting to fall over, being lighter weight and 
all.  The idea of building faster and improved insulation value with this 
method is, of course, appealing, but do you think there is a greater risk of 
having bug problems in a straw-clay wall than a cob wall?  </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>I am not inclined to building with straw bales as I 
have heard too many stories of problems with bugs and rot.  Am I being 
paranoid as we live in a semi-arid climate here?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Thanks for your input.</FONT></DIV>
<DIV><FONT face=Arial size=2>Robynn</FONT></DIV>
<DIV> </DIV>
<BLOCKQUOTE 
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
  <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV 
  style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> 
  <A href="mailto:wfirstb1 at wcb.bc.ca" title=wfirstb1 at wcb.bc.ca>Firstbrook, 
  Will</A> </DIV>
  <DIV style="FONT: 10pt arial"><B>To:</B> <A 
  href="mailto:ironfire at cyberlink.bc.ca" title=ironfire at cyberlink.bc.ca>'Shawn 
  Honeychurch'</A> ; <A href="mailto:coblist at deatech.com" 
  title=coblist at deatech.com>coblist at deatech.com</A> </DIV>
  <DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, November 01, 2000 11:19 
  AM</DIV>
  <DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Posts embedded in cob</DIV>
  <DIV><BR></DIV>
  <P><FONT size=2>Hi Shawn and Robynn,</FONT> </P>
  <P><FONT size=2>The cob as it shrinks/dies will separate from the embedded 
  posts. Which might not be a problem if the wall is quite thick surrounding the 
  posts. If the cob is thin around the post it will crack. Also since you intend 
  to have straight walls with the post in the corners the wall will be weak in 
  the corners. The strength of cob would be compromised in that design. Not a 
  good idea in an earthquake zone. Note that straight walls are considerably 
  weaker than curved walls. One of the things I love about cob is the organic 
  curved walls.</FONT></P>
  <P><FONT size=2>Some options you might want to consider:</FONT> </P>
  <P><FONT size=2>Make the cob loadbearing, build temporary posts holding the 
  roof then build the cob walls put a top plate on and lower the roof onto the 
  cob. Curve the corners for greater strength.</FONT></P>
  <P><FONT size=2>Leichlehmbau (often refered to as light clay or straw-clay). 
  Using your current ideas make temporary forms for the walls and pack straw 
  dipped into a clay slip into the forms, once the walls have hardened remove 
  the forms and plaster both sides of the wall with cob plasters. The advantages 
  of this technique are much improved insulation value, faster construction time 
  & lighter walls. You can put lots of cob on the inside of the wall to 
  provide mass.</FONT></P>
  <P><FONT size=2>Load bearing or modified post and beam strawbale construction 
  can easily give straight walls and strong corners.</FONT> </P>
  <P><FONT size=2>Regards,</FONT> <BR><FONT size=2>Will</FONT> </P><BR><BR><BR>
  <P><FONT size=2>-----Original Message-----</FONT> <BR><FONT size=2>From: Shawn 
  Honeychurch [<A 
  href="mailto:ironfire at cyberlink.bc.ca">mailto:ironfire at cyberlink.bc.ca</A>]</FONT> 
  <BR><FONT size=2>Sent: Tuesday, October 31, 2000 7:06 AM</FONT> <BR><FONT 
  size=2>To: coblist at deatech.com</FONT> <BR><FONT size=2>Subject: Cob: Posts 
  embedded in cob</FONT> </P><BR>
  <P><FONT size=2>Hi All;</FONT> </P>
  <P><FONT size=2>We are planning to build a post and beam style house with cob 
  walls.  We are</FONT> <BR><FONT size=2>going to build short sections of 
  straight cobs walls between the posts using</FONT> <BR><FONT size=2>forms and 
  shape the cob around the posts so that the finished house will not</FONT> 
  <BR><FONT size=2>have any posts showing.  We were just reading in the 
  "Cob Builders Handbook"</FONT> <BR><FONT size=2>that this is not suggested due 
  to the shrinkage of the cob while it is</FONT> <BR><FONT size=2>drying.</FONT> 
  <BR><FONT size=2>Has anyone tried this, or does anyone have suggestions on how 
  to get around</FONT> <BR><FONT size=2>this problem so we don't have to totally 
  redesign the house?</FONT> </P>
  <P><FONT size=2>Shawn and Robynn</FONT> </P></BLOCKQUOTE></BODY></HTML>