[Cob] opinion on foundation for cob

[phil moulton]

My big concern is just what the last poster said.
Putting a gravel trench down means a unstable stem wall.
Most here might say put in a "urbanite" and concrete stem wall over gravel.
I just do not feel its stable enough. We are not talking about a stick frame
wall but tons of material.
I know there are those who feel I am not "green" and that's ok.
Even if you let it settle for a few years and machine tamp it down its still
gravel with a drain pipe in it.


When we build it will be on solid ground with rebar and a solid concrete
pour 18 inch wide and 2 feet high.
It will start with a good solid footing of undisturbed earth. If that's 5
inches down or 20 the undisturbed earth has been there and is nicely settled
into its home.

Putting a stem wall over a gravel drain trench WILL cause it to crack...
Put your gravel drain trench OUTSIDE the perimeter of the stem wall so it
deflects any water around the foundation. 

Phil and lilpony

-----Original Message-----
From: coblist-bounces at deatech.com [mailto:coblist-bounces at deatech.com] On
Behalf Of Tys Sniffen
Sent: Saturday, June 27, 2009 9:23 PM
To: coblist at deatech.com
Subject: [Cob] opinion on foundation for cob

Kristin,

 

My opinion (worth everything you paid for it) would be close to what you're
thinking.  If you've got a stable foundation (of any sort), get down below
the topsoil and then build up a stem wall. BUT, I would also suggest going
further down  (9 inches or so?) and a bit wider than your wall and making a
gravel trench (with drainage tube) so that your stem  wall can 'float' on
that.  Also, I'd suggest you get the stem wall up and let it dry totally,
and ideally do any settling it was going to do before you put tons of cob on
top of it. 

 

About determining the stability of your area, you should look into some
local geological history, and then just sit out in the spot and think it
through. Look at the land as if you could imagine the area flowing like lava
through time. Is there a dip below your building spot? Is there a crusty,
breaking off cliff above it? Imagine what the earth in that area has been
doing for the last 1000 years, and that's probably what will happen in the
next 1000.

Tys

 

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