[Cob] Curious about the clay

[Marlin Nissen]

my 2 cents,,,,, had best luck with the clay that I got from a road construction crew (don't know if you have clay in your area) where they called it "road cut" and was ONLY subsoil clay with huge hard clods in it that were virtually plastic when cut into. The test bricks with that and 4 X the sand (sharp sand from a quarry, not beach sand) was incredibly good Cob. You have to test the amounts of each but if it's PURE clay it won't take nearly as much (takes more when you're dealing with silt/organics in the soil) and will be much stronger. Also the sand quality (sharp, larger granules) makes better Cob in my experience. Beach sand crumbles..

I jumped up into the back of the 'clay' truck to make sure it was cloddy and it was grey in color (could be orange too) before they dumped it.....like I said the clay went so far that we ended up with a huge excess pile of it....the sand went quicker but it was easier to find when we needed more. I also used the grey/smeary clay to waterproof the block foundation for the greenhouse as this stuff was gummy and water resistant.

The caveat is that clay like that, while amazingly sticky, takes awhile to breakdown enuff to work with..........soaked a bunch of it, pulverized others with a tiller and a pit and "screeded" clods on a framed wire rack into a wheelbarrow to get fine clay dust for plaster.

I don't know (actually doubt) that pottery clay is your best way to go but I'd be interested to know if someone has worked with it,,,,,,

Best,

Marlin (Upper Midwest soils ARE clay mostly)

p.s. oh yeah and covering the piles while dry is a really good idea!

--- On Mon, 5/11/09, Robert J Churchill <rjc2000 at pacbell.net> wrote:

From: Robert J Churchill <rjc2000 at pacbell.net>
Subject: Re: [Cob] Curious about the clay
To: 
Cc: coblist at deatech.com
Date: Monday, May 11, 2009, 1:17 AM

I know going in that it's not cheap but money really isn't a problem.  What is a problem is I don't want to build a structure and have it fall down because the clay sucked.  So I'm more interested in experiences with commercial clay or even quarry clay, not just dirt with clay in it.

--- On Thu, 5/7/09, Henry Raduazo <raduazo at cox.net> wrote:
From: Henry Raduazo <raduazo at cox.net>
Subject: Re: [Cob] Curious about the clay
To: rjc2000 at pacbell.net
Cc: coblist at deatech.com
Date: Thursday, May 7, 2009, 5:04 AM

Clay is one of the most common substances on earth as such many people have it
available for free. Just go outside and dig it up. With that said every part of
the earth differs from every other part of the earth. Some people have very pure
clay which shrinks drastically as it dries some have clay and silt some clay and
sand. Others have no clay or so little clay their walls will barely hold
together.
    If you do not have a good supply of naturally occurring clay in your area I
would not recommend building with cob. A fairly small wall that I built in my
house as a heat sink weighs 8 tons. I bought 4 tons of sand ($20.00 per ton) and
mixed that with 4 tons of clay rich soil that came from digging out the basement
of a near by house. The contractor was going to haul the soil 60 miles and pay a
tipping fee to get rid of it, but I was willing to take it for free. Buying that
much clay at a pottery place would be a bit pricey.
    Anyone who would be a natural builder must first be a scientist and then be an
engineer. As a scientist you look around your building cite and ask What do I
have? Rocks? Trees? Clay? All can be converted to building materials. Clay is
one of the most versatile because it has so many uses as a plaster, load bearing
material or refractory. You need to experiment to find the best mix. Sometimes
you need to add sand sometimes just straw. You make bricks and then destroy the
bricks to determine the best combination of materials.
    When you know the best combination of materials then you become an engineer
and ask yourself "How do I make 8 tons of this stuff?" I like to mix
with a rototiller on a slab. You may want to mix with your feet on a tarp. What
ever. You need a lot of stuff to build a house.
Ed
On May 7, 2009, at 1:19 AM, Robert J Churchill wrote:
> The word "clay" is used repeatedly but really where exactly is
all this clay coming from?  I have no idea where I'm supposed to get all
this clay.  For me, it would be easier just to buy clay from a ceramics shop but
I don't even know if that would work.  I live in an urban area and it's
not like we can just go out and dig up clay at a local quarry.
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