Cob: RE: Cob/light clay hybrid with a foundation question

Fri Apr 20 14:23:26 CDT 2001

Hi Karen,

I enjoy your questions, these are all ideas I have tossed around in my mind.
I live in the BC interior.

I was thinking for my addition of making a hybrid frost protected rubble
trench by installing some Styrofoam underground in the rubble trench near
the outer side of the trench. So it does provide insulation value but it is
still imbedded in the drain rocks so it should stay relatively dry. Then the
floor of the structure can be part of the thermal mass.

I am fortunate in that my structure is out of the code jurisdiction. However
structurally I do intend to exceed the code standards. In your regional
climate,  Edmonton gets darn cold in the winter, I would think cob without
an insulating sweater would be somewhat uncomfortable. My parents once owned
a stone farmhouse in Ontario we used as a ski cabin. The 18" stone walls
were perpetually cold. This is why I am proposing to use a hybrid of straw
and cob, based on my earlier email.

1. Ultimately you will have to make that choice based on all sorts of
factors. Regarding the code, if you tell the inspectors that the structure
is post and beam stucco structure with R20 insulation on a Frank Lloyd
Wright rubble trench foundation it might be easier to sell to the inspector.

2. I believe excess heat does cause cracking in drying cob. For sure it
caused my earthen floor to crack considerably more near the woodstove. I
would expect it would not harm drying light clay at all. This is one of the
reasons why I am thinking of building my hybrid.

3. I think your third (question?) is the way to go. Allowing the straw to
dry before it gets to the point of decomposing. Then building the interior
cob.

Regarding the wicking of moisture to the straw from the foundation. In my
strawbale house I lifted the straw off the foundation utilizing wood then
made a little box out of 2x4's filled with pea gravel and covered with tar
paper. So no water can wick-up into the bales. Also if water spills on the
floor it doesn't end-up in the bales.

Regards,
Will  

-----Original Message-----
From: Dog In The Yard [mailto:dognyard at worldgate.com]
Sent: Thursday, April 19, 2001 2:30 PM
To: coblist at deatech.com
Subject: Cob: Cob/light clay hybrid with a foundation question

I really appreciate all the feedback! Thank you to everyone.

I have it mind to try a very small "trial building" of some hybrid or other.
Mostly to play and experiment with what works and doesn't in my regional
climate. I find my head full of ideas and "what ifs". I think that one of
the
joys of considering building with one's own hands is the inherent energy it
gives you...both in the thinking stages and in the actual building stages.

This project is for me to learn with. I wish to try either a shallow, frost
protected foundation or a rubble trench...heck...I might even try both, on
alternate sides of the building. If the building remains standing once it is
complete, it will either become a storage shed, or if it's large enough, a
horse shelter.

I would like to heat the building, at least at the outset, so see how the
heat
works within the building (haven't decided yet how it will be heated, other
than
knowing it will be low tech :-)). This leads me to ask questions such as:

1) What hybrid should I chose? Strawbale/cob? Or Cob/Slipstraw? If I want it
to
meet local codes, those local codes will demand a version of wood frame
construction...if I go this route I will be "infilling" wood framed walls.

2) How will the heat effect the curing of the cob on the interior walls?
Would
it offset (or prevent) the freezing of the exterior of the wall?

3) If I choose to use light clay (or slipstraw), could I finish the exterior
wall, and leave the interior wall unfinished for a time while heating the
building to help the slipstraw cure, then finish the interior later? (My
whole
reason for wanting to try slipstraw over the use of whole straw bales is
simply
that I want to try it and see how it works.)

Because the building will be a trial (my "mistake building"), I have no
particular time frame I must adhere to, and no real rules I must obey other
than
those of nature if I want the building to remain upright :-).

I was also thinking of going ahead and trying a honeycomb type layout of the
cob...I can alway tear it up and start over. I was also thinking of trying
the
slipstraw and leaving it exposed on the interior to aid in drying (if I use
a
wood frame, that is).

I am excited about the prospect of all these new challenges...trying out the
foundations, earthen floors, various plaster techniques. I'm an avidly
curious
individual who likes to try new things and take on new challenges (although
I
honestly believe in learning from other people's mistakes). When I die, I
hope
to die of curiosity:-).

I do have an additional question regarding foundations...Somewhere in all
the
reading I've been doing lately, I understand that it is not such a good
thing to
have straw in direct contact with cement foundations because of possible
wicking...but do I understand correctly that stone is ok? I saw  reference
somewhere to using gravel in earth bags (?) along the top of the
foundation...has anyone any experience with this?

Thanks again for all the feedback and ideas.

Karen Clouston
Edmonton, Alberta
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<P><FONT SIZE=2>Hi Karen,</FONT>
</P>

I enjoy your questions, these are all ideas I have tossed around in my mind. I live in the BC interior.

I was thinking for my addition of making a hybrid frost protected rubble trench by installing some Styrofoam underground in the rubble trench near the outer side of the trench. So it does provide insulation value but it is still imbedded in the drain rocks so it should stay relatively dry. Then the floor of the structure can be part of the thermal mass.

I am fortunate in that my structure is out of the code jurisdiction. However structurally I do intend to exceed the code standards. In your regional climate,  Edmonton gets darn cold in the winter, I would think cob without an insulating sweater would be somewhat uncomfortable. My parents once owned a stone farmhouse in Ontario we used as a ski cabin. The 18" stone walls were perpetually cold. This is why I am proposing to use a hybrid of straw and cob, based on my earlier email.

1. Ultimately you will have to make that choice based on all sorts of factors. Regarding the code, if you tell the inspectors that the structure is post and beam stucco structure with R20 insulation on a Frank Lloyd Wright rubble trench foundation it might be easier to sell to the inspector.

2. I believe excess heat does cause cracking in drying cob. For sure it caused my earthen floor to crack considerably more near the woodstove. I would expect it would not harm drying light clay at all. This is one of the reasons why I am thinking of building my hybrid.

3. I think your third (question?) is the way to go. Allowing the straw to dry before it gets to the point of decomposing. Then building the interior cob.

Regarding the wicking of moisture to the straw from the foundation. In my strawbale house I lifted the straw off the foundation utilizing wood then made a little box out of 2x4's filled with pea gravel and covered with tar paper. So no water can wick-up into the bales. Also if water spills on the floor it doesn't end-up in the bales.

<P><FONT SIZE=2>Regards,</FONT>
<BR><FONT SIZE=2>Will  </FONT>
</P>
<BR>

<P><FONT SIZE=2>-----Original Message-----</FONT>
<BR><FONT SIZE=2>From: Dog In The Yard [<A HREF="mailto:dognyard at worldgate.com">mailto:dognyard at worldgate.com</A>]</FONT>
<BR><FONT SIZE=2>Sent: Thursday, April 19, 2001 2:30 PM</FONT>
<BR><FONT SIZE=2>To: coblist at deatech.com</FONT>
<BR><FONT SIZE=2>Subject: Cob: Cob/light clay hybrid with a foundation question</FONT>
</P>
<BR>

I really appreciate all the feedback! Thank you to everyone.

I have it mind to try a very small "trial building" of some hybrid or other.
 Mostly to play and experiment with what works and doesn't in my regional
 climate. I find my head full of ideas and "what ifs". I think that one of the
 joys of considering building with one's own hands is the inherent energy it
 gives you...both in the thinking stages and in the actual building stages.

This project is for me to learn with. I wish to try either a shallow, frost
 protected foundation or a rubble trench...heck...I might even try both, on
 alternate sides of the building. If the building remains standing once it is
 complete, it will either become a storage shed, or if it's large enough, a horse shelter.

I would like to heat the building, at least at the outset, so see how the heat
 works within the building (haven't decided yet how it will be heated, other than
 knowing it will be low tech :-)). This leads me to ask questions such as:

1) What hybrid should I chose? Strawbale/cob? Or Cob/Slipstraw? If I want it to
 meet local codes, those local codes will demand a version of wood frame
 construction...if I go this route I will be "infilling" wood framed walls.

2) How will the heat effect the curing of the cob on the interior walls? Would
 it offset (or prevent) the freezing of the exterior of the wall?

3) If I choose to use light clay (or slipstraw), could I finish the exterior
 wall, and leave the interior wall unfinished for a time while heating the
 building to help the slipstraw cure, then finish the interior later? (My whole
 reason for wanting to try slipstraw over the use of whole straw bales is simply
 that I want to try it and see how it works.)

<P><FONT SIZE=2>Because the building will be a trial (my "mistake building"), I have no</FONT>
<BR><FONT SIZE=2>particular time frame I must adhere to, and no real rules I must obey other than</FONT>
<BR><FONT SIZE=2>those of nature if I want the building to remain upright :-).</FONT>
</P>

I was also thinking of going ahead and trying a honeycomb type layout of the
 cob...I can alway tear it up and start over. I was also thinking of trying the
 slipstraw and leaving it exposed on the interior to aid in drying (if I use a
 wood frame, that is).

I am excited about the prospect of all these new challenges...trying out the
 foundations, earthen floors, various plaster techniques. I'm an avidly curious
 individual who likes to try new things and take on new challenges (although I
 honestly believe in learning from other people's mistakes). When I die, I hope
 to die of curiosity:-).

I do have an additional question regarding foundations...Somewhere in all the
 reading I've been doing lately, I understand that it is not such a good thing to
 have straw in direct contact with cement foundations because of possible
 wicking...but do I understand correctly that stone is ok? I saw  reference
 somewhere to using gravel in earth bags (?) along the top of the
 foundation...has anyone any experience with this?

<P><FONT SIZE=2>Thanks again for all the feedback and ideas.</FONT>
</P>

<P><FONT SIZE=2>Karen Clouston</FONT>
<BR><FONT SIZE=2>Edmonton, Alberta</FONT>
</P>

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