Cob: foundation ? why ?

[Shannon C. Dealy]

On Wed, 2 Aug 2000, olivier Tallendier wrote:

> does cob house need really foundation ?
> 
> I have seen some house today directly build on the ground.
> ( i'm still in india )
> 
> if the foundation are made to protect the walls from humidity,
> why not clean the ground, put a mix of stones and lime on the ground
> ( like a drain )
> and directly build the wall on it ?
> after to protect the wall from water why not put stones on the foot of the 
> wall and dig a kind of drain all around the house ?

All of the reasons I can think of (there may be some I haven't thought of)
to have a foundation under cob are as follows:

   1 - Prevent frost heave from shifting the building and damaging the
       walls.
   2 - Get the wall off the ground so that water from the ground
       will not seep into the wall.
   3 - Get the wall high enough off the ground so that rain splash will
       not errode the wall.  What I am referring to here is raindrops
       hitting the ground and splattering onto the wall.  In a couple of
       buildings I have looked at, errosion from this is a significant
       problem, where wind driven rain which directly impacts the walls
       has little or no effect.
   4 - Create a more stable base for the wall if the ground is not stable
       enough to directly support it.
   5 - To appease local building authorities so they will give you a
       permit.

If these items do not apply to your application or are otherwise dealt
with, I see no reason why you couldn't build it directly on the ground.
Item three above might possibly be dealt with by embedding large flat
rocks in the outside of the bottom of the wall, or just plastering the
outside of the base of the wall on a regular basis.

Shannon C. Dealy      |               DeaTech Research Inc.
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