[Cob] Land search...pressed earth blocks vs. cob

[Lance Collins]

Hi Amanda et al,

>Speed of production on the CEBs has attracted me to them.  There seem to 
>be two (or three if you can count adobe) basic kinds.  With the first-- 
>blocks made with a machine like the Cinva Ram, not too expensive (some 
>under $1000)--do seem to have to cure before you can build.  And making 
>the block might be a pretty arduous task.  Somebody here's doing it, we'd 
>like a report!

As a learning experience I have built an internal wall to separate off some 
living space from the workshop/storage area of my shed.  The wall is 10 
metres long and almost 3 metres high.   The bottom half was done with 
formwork and various mixes and the top half with blocks.   Along the way I 
bought a Dalrac press second hand for $A250.  The original owner was lucky, 
his clay and sand soil made great blocks without any additives or 
pre-mixing.   My initial attempts at block making were a failure, I could 
not make a block which stuck together when dry.  Recently I tried some soil 
from about twenty metres away which has a little more red clay and the 
blocks are quite good.

Making the blocks is fairly easy especially when you learn some tricks like 
placing a phone book page in the hopper first and having a piece of wood to 
slide the compressed block onto before stacking it.

But I have decided I don't like blocks compared with formwork cob.   Blocks 
are time consuming to lay and at the present I am plastering my wall and 
finding that the formwork wall is easy to plaster and the rougher block 
wall is much slower and harder work.

My experimental formwork was made with pine lining boards, cheap as I had 
bought a pack lot for another job but very tedious to set up and tear 
down.   I am currently investigating making or buying more substantial and 
easier to use formwork for my house project.

I would not recommend buying any kind of block making machine until you are 
sure it will work with your soil.

After I'd done a three layers of cob I was concerned that each layer was 
taking too long to dry but I've now developed a mixture of soil, sawdust, 
cement and lime which makes good blocks and even better mortar between 
blocks.  The cement and lime overcome shrinkage  and are firm enough to 
support another rise within 24 hours.  I'm confident this mix will be ideal 
for making my house walls.

Cheers

Lance