Cob: sandy soil

[dtebb]

>    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

Hi Sara,

It sounds to me like you may have silt. Silt looks and feels alot like clay
but it is not very sticky and for sure a silty brick will be very soft and
crumbly. I don't know if there are clays that are not sticky. Does anybody
know about this.

Ian Marcuse