Cob: RE: sandy soil

[Patrick Newberry]

Hi Sara, 
 
 I too have very sandy soil here in Mauk. As a result I have to bring
clay in to the building site. My soil mix, using the jar and water test
comes in 
around 20 percent clay, sometimes as low as 10 percent. Now I have found
that one, using a lot of straw and juding based on the walls themselves 
rather than test bricks that it's quite sturdy. My son backed our pickup
(not real hard, but hard enough) into one wall by accident and it
aborbed the 
shock not problem-o 
 
One advantage to the sandy soil is that the water does not tend to
puddle for very long. We have very heavy rains and with in a short
period of 
time the water seeps down. I have used earthbags filled with the sandy
soil and cement and they have worked fine. I only go up about a little
less 
than a foot before I switch to cob. 
 
As far as  floor, tamping sand doesn't quite do as well as tamping a
more clay-ey soil. 
 
What size are you going to build your emergency shelter?
 
Pat 
http://www.gnat.net/~goshawk <http://www.gnat.net/~goshawk> 
 
 

-----Original Message-----
From: Sbay [mailto:Hi_eagle at hotmail.com]
Sent: Sunday, September 30, 2001 11:58 PM
To: coblist at deatech.com
Subject: Cob: sandy soil


Hello,
I am new to this lovely list so I will start by introducing myself.
My name is Sara.  I found cob about a year ago.  I was exploring green
building, always thinking there's got to be a better way.  Then I found
cob.
I am in need of an emergency type shelter that should last for a while
so my kids can use it after we get a more permanant home.
I'd love to go all cob, but codes and stuff will force us to build
either conventional or log.
Anyway, our soil is extremely sandy.   Actually it is sand, all sand,
nothing but sand.  I had some clay brought in but it is not the best
quality.  Nothing like
the clay I used this spring from a lakeshore to build little test
structures with my kids.  This stuff is not very sticky, really light
tan and kinda sandy or something.
So, do I need to bring in some better clay?  Or just use more than the
advised amount of our sandy, not so sticky clay????
I've made test bricks with 50/50 and they weren't as solid as i'd hoped.

Also I'm not going to build a foundation, so do I need to put the cob a
little below ground or just slap it right down on the grass?
And what should I do for a bare bones floor?  Just move the grass and
tamp the earth some?
Thanks
Sara