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Kiko Denzer on Art



[Cob] Re: How to get a straight wall with cob

Christopher Peters bollygum211 at dodo.com.au
Sun Mar 6 03:18:35 CST 2005


G'day Lorraine,

At a guess it sounds like perhaps it needed a little more mixing till the
batch had a consistent moisture level with evenly dispersed clay particles
throughout. Have you tried leaving the batch to sit overnight ? This will
help with some of the really dry soils types here in Oz. Was this mixing
using a tarp, pit or with machinery ?

Here in the Bega Valley NSW, we've decomposed granite subsoils which set
like their parent rock but are a bugger to mix by foot without making the
mix too wet. By adding a red medium clay (basalt derived) gave me an
excellent cob mix. I add only a barrow load to each ute load of the granite
soil but it did the trick. In my case it was worth trying all the soils on
the block and even mixing a few.

A simple field test of dissolving a handful of soil in a jar and leaving it
to settle into particle sizes adds a few more clues to a useful soil.

What soil type are you using in SA ? have you any photos of this troublesome
mix you could share with us..

Have you read "Building a house in a day" by Ron Edwards ? it's a good
starter and available from the Owner Builder Mag's Bookshop,
www.theownerbuilder.com.au  which I have no connection with, just a happy
customer :-)

cheers
& good to hear of a fellow cobber here downunder,
chris


>From: "Bob & Lorraine" <farmlink at bigpond.com>
>Subject: [Cob] How to get a straight wall with cob?
>
>
>
>Today we started our first cob wall.  It's brought us to some questions
>I hope more experienced cobbers can help me with.
>
>
>
>What should a good mix look and feel like?
>
>Ours was patchy with some parts of it having a smooth, plasticiny feel,
>some lumpy/gritty although wet, and some being a bit dryish and rubbly.
>We tried various methods - forking whatever we came to onto the
>foundation and patting it into shape, pressing it into cobs with our
>hands then incorporating it onto the wall, and doing more mixing in the
>mud pile before forking it onto the foundation.
<snip>