[Cob] Types of clay, building in Toronto

[Georgie Donais]

All,

Thanks to Alex for the information regarding types of clay; it helps to 
clarify some information I've recently received. Also, Canadian straw/clay 
building guru Dan Boileau was just telling me how he employs the same 
labour-saving technique as Karen with his clay. He exposes it to winter 
weather and, every spring, can scrape off about an inch of perfectly 
powdered clay for building use.

Meanwhile, our Cob in the Park project is steaming along. We have just 
completed the foundation, and will start cobbing on Saturday! Check out the 
pics at www.cobinthepark.ca .

Georgie

Alex wrote (snipped):

>2. Lumps of subsoil with very high clay content do not usualy 'dissolve'
>when soaked. Which is a shame, because it means if your soil has a lot of
>what looks like potters clay in it you are going to have more work to do!
>Clay will quite happily sit in water without doing anything for a long time,
>hence it is used to line ponds and pits in landfill sites. To make good cob
>from this type of subsoil you will need to break it down, usually better
>done when it is dry, because clay becomes plastic and sticky when wet,
>making it harder to break up.
>We know this becuase we have built cob structures using many types of
>subsoil. You need to keep in mind that many of the older cob buildings here
>in Devon and Cornwall have only around 15% clay in the cob mix, the rest is
>silt, sand, rock and straw.
>If your soil dissolves in water then it probably has a lot of silt and sand
>in it and you may be in for an easier ride!

Karen wrote (snipped):

>We have this kind of soil! I can literally make sculpture with it with
>very little amendment. Since we live with this soil every day, we
>learned a few things about it. One is how to break it down easier. Let
>nature do it. We have bitterly cold winters, which I believe helps the
>breaking-down process.
>
>If you can plan ahead, you dig it out and simply pile it...then let it
>sit over the winter. By next spring - ta-da! - it becomes very granular
>and easy to use. Near as I can tell, it's simply the action of freezing
>and thawing working on the water content in the clay.