Cob: RE: RE: Posts embedded in cob

[Shawn Honeychurch]

Hey, this is great to know!
Where we are there is rarely ever a hard rain.  With large overhangs and
proper gutters and drainage around the perimeter of the house, I could
probably get away with a 1 foot foundation (above ground), then.  I am still
wondering about how to make a water proof  barrier between cob and
foundation if the foundation needs to be rough to stick to the cob.  If we
laid plastic on the top of a stone and mortar foundation, do you think this
would do the trick?  Would the cob still stick to that?
Robynn



----- Original Message -----
From: "Shannon C. Dealy" <dealy at deatech.com>
To: "Firstbrook, Will" <wfirstb1 at wcb.bc.ca>
Cc: "'Shawn Honeychurch'" <ironfire at cyberlink.bc.ca>; <coblist at deatech.com>
Sent: Thursday, November 02, 2000 8:16 PM
Subject: Re: Cob: RE: RE: Posts embedded in cob


> On Thu, 2 Nov 2000, Firstbrook, Will wrote:
>
> [snip]
> > Regarding your design, my understanding is the cob should start approx.
2'
> > above ground at least on the exterior so no water can be wicked up into
the
> > cob. Also the foundation that cob sits on should ideally be rough so the
the
> [snip]
>
> Actually, preventing wicking is not a matter of height, a one inch above
> ground foundation with a waterproof barrier in it could do that providing
> no standing water around the structure ever reaches the height at which
> the water proof barrier is located.  Wicking through even a quite short
> concrete or rock foundation (without added water proofing) is unlikely to
> have any effect on a cob wall unless the foundation is in standing water,
> and possibly not even then.  The main reason that I am aware of for the
> high foundation is that when rain hits the ground (or plants or other
> objects near the base of your wall) it splashes onto the wall and can/will
> cause errosion in your wall.  I have seen this effect on a couple of cob
> structures (I actually stood out in the rain watching it for a while) and
> was surprized at how much greater the damage was from the rain hitting the
> ground or bushes and splashing the wall than it was from the rain which
> hit the wall directly.  From what I saw, rain hitting the wall directly
> was minimal (due in part to the roof overhang) and tended to be absorbed
> into the dry cob wall (rather than running down and erroding it), but of
> course there was lots of rain hitting the ground and bushes around the
> base of the buildings, and run off from the roof (which had no gutters)
> greatly added to the water hitting the ground all around the perimeter of
> the building.  The combination of rain and run-off caused the base of the
> wall to be splashed continuously up to a height of a couple feet leaving
> the base of the wall looking quite damp even a couple days after the rain
> stopped.  There were also small but easily visible errosion tracks running
> down the surface of the cob that was located within 1-1/2 to two feet of
> ground level.
>
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
>                       |    Embedded Systems, Real-time, Device Drivers
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>
>