[Cob] Urea as Binder in Cob (long post)

[Mahavir Mahedu]

Hi everyone,

Thank you very much for your responses.

Andrew is right, by drywall I mean random rubble without any sort of mortar. This is an art and a very old and time tested technology. There are many experts of this technology in my area. I recently photographed an entire house built by drywall technique in a seismic zone 5 , which is some 300 kms from my site. It has survived an earthquake of 8 on richters scale. But still, it is different to build a foundation by drywall technique and then a cob wall on it.

But I have decided to go with it. 

We have a very old tradition of building cob houses in India, but the houses are limited to small modest dwellings for the poor. We don't have huge houses like they have in UK. A community named "Od" is well known for this tradition and they generally build house of circular shape known as either "kooba" or "bhunga". Although the UK method is far superior.

A weed with higher urea content was an interesting suggetion.

Also, how about adding a plasticiser like ligno sulphonate to the cob ?  Has anyone tried this ?

Mahavir.


----- Original Message ----
From: Shody Ryon <qi4u at yahoo.com>
To: coblist at deatech.com
Sent: Saturday, 20 October, 2007 10:32:56 PM
Subject: Re: [Cob] Urea as Binder in Cob (long post)

Hi Mahavir,
This sounds like a wonderful project.
I have not built a cob house. I do not think it is
generally safe to build a drywall foundation, if by
drywall you mean gypsum board, which is usually used
in fairly dry non structural applications and interior
location. I have seen it used on what looked like the
exterior of a commercial building during construction.
It may have been eventually covered with something and
it was installed under a big overhang. It was the
green kind of drywall that was used in slightly wetter
locations such as bathrooms and kitchen interiors. The
latest that I have heard about drywall is the use of
paperless drywall that is likely less toxic than I
assume the papered drywall is. I do not understand how
a foundation would be made from drywall, would it be
several gypsum board sandwiched together until a 6 or
8” wall is formed? What is commonly done is concrete
rubble is put into a foundation trench, if I
understand correctly. I imagine that you could use
rock rubble if that is more plentiful in your area. Do
you have access to a lot of drywall?
As I recall, I have heard that the common weed
purslane has urea in it that might be able to be used
as a fertilizer.
Purslane is almost like a succulent plant and I have
seen local (to southern California) succulent plant
leaves put in a trash can with water to make what the
builder called musulage (unknown spelling). He let it
soak as long as possible, days or longer and used that
to mix with the earth.

I would consider making the walls think and low and
thinner as the wall increases in highth and the use of
a beam in the top of the wall, if I were doing it. I
would also make test samples of earthen bricks to see
how strong they are with different mixes and what
happenes to them when they dry.

Cheers,
Shody

--- Mahavir Mahedu <lonthia at yahoo.co.in> wrote:

> Hi everybody,
> 
> I am planning to build a cob house with thatched
> roof in India.
<snip>

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