Cob: Re: light clay infill question

[stefanson]

Hello Shae,

We initially thought of doing the exact same thing as temporary shelter
while building a cob house, however, I determined that the light clay infill
wasn't practical. A stick frame building isn't strong enough in itself to
stand up to really strong winds & earthquakes. It needs a sheathing material
such as OSB/Plywood for racking strength. But the light clay needs to be
able to move moisture from the inside to the outside, so you might have a
problem if you had sheathing on the outside (but maybe not, I'm certainly
not an expert). I've heard of people using it as attic insulation, but that
typically has an inch or so of breathing space to help moisture evaporate.
Typically light clay is done as infill on post&beam, which is sturdy enough
in itself, and the walls are really thick.

Perhaps you can be creative to cut down on costs. You will need sheathing
for the exterior, but maybe you can find surplus somewhere? Ask businesses
that have stuff shipped to them in crates if you can have the crates, which
are usually constructed of a pallet with plywood/OSB sides, then you can use
the plywood/OSB for sheathing and the slats on the pallet for interior walls
:), and use recycled material for insulation (papercrete, soymilk
containers, whatever you can find that has air space).

Good Luck,
-Cari

----- Original Message -----
From: "Shae Tebbetts" <yourelovedbygod at hotmail.com>
To: <coblist at deatech.com>
Sent: Saturday, January 18, 2003 8:19 PM
Subject: Cob: light clay infill question


>
> Hi all,
>
> We finally bought our land.  I looked up our states geological maps to
find
> the best land for cob building that was closest to dh place of employment.
> It is a 6 acre hill full of sandstone, slate and clay with a creek at the
> bottom.  We had been living in a tent since May 2002, with plans of
building
> a small cob room the first year and then building onto that the following
> years.  Anyway, to make a long story short, our military tent along with
all
> our household items burned to the ground due to our own carelessness
(makes
> me sick to think about).  So we had to move in with our inlaws since we
have
> 2 children.  That has changed plans a lot.  Now we need a home quick!  So
> we've started building a stick frame cabin.  It will be small, yet all the
> space we need to give us plenty of time to build the cob house.
>
> My concern is that I don't want us to sink a lot of money into this cabin.
> The foundation is sortof a pier system with the floor off the ground.  My
> father in law got involved in this, so alot of this has been his ideas up
> until now since he's helping us financially, etc. etc.
>
> Well my question is this:  I want to use light clay straw to fill the
> traditional stud walls.  My understanding is that light clay straw is
> typically setting on the ground or a stem wall.  My concern is will the
> floor,.which is suspended off the ground with piers, be able to bear the
> weight of the light clay wall infill.  We won't have an inner or outer
> sheathing, but rather cob plaster in and out.  I'm thinking it would
> probably work if the light clay walls are only 3.5" thick because we have
> been overbuilding a bit so far...piers are every 3.5-4 feet.  The beams
> (under the joists? are 2"x8"s and they are every 3.5 feet.  Then the
joists
> are 2"x8"s and they are on 16" centers.  I have no idea of how to do the
> calculations to see if this will work.  I think light clay straw is 30-50
lb
> per sf depending on the quality of clay.  Lath may be necessary, but I'm
> hoping we can get around it somehow.  I was thinking that we could always
> add a retaining wall later for additional support using all the really
great
> stones we have.
>
> I need some input as to whether anyone thinks the floor will be able to
> carry this load or not.  If so, should we just stick with 3.5" or how
thick
> of a wall do you think we can get by with?
>
> Thanks,
> shae
>
>
>
>
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