Cob: just a couple things I don't understand

[Shannon C. Dealy]

On Sun, 29 Sep 2002, Howard wrote:

[snip]
> the sort Hassan Fathy is well known for.  (Shannon, what 's the guys name with
> CalEarth, I think, who is carrying on that kind of work?)  You need to make dry

Nader Khalili

> hardened "cob" bricks that you can then lay up into a dome shape.  When Shannon says
> she knows of no "cob roofs" she is referring to the specific method of cob

You are correct.

> construction that deals only with walls in a wet mud monolithic manner which would
> be difficult to build a dome with, at least without a form.  But cob is earth, sand
> and straw just as the adobe bricks that have formed domed roofs are.  This method of
> dome building comes from very dry regions where they don't have timber with which to
> build a roof and if the current desertification of the planet continues we may all

The earthen roof building techniques that I know of (there are probably
others) are generally either heavily reinforced/supported (typically with
logs), or are built as vaults, and with the exception of vaults which have
been fired to form a ceramic, I don't consider either of these techniques
safe in any climate which can receive any significant amount of rainfall.
The problem with attempting to use cob for these techniques is that the
cob is wet when it is put up which means it is both very soft and very
heavy, where adobe block is put up dry which means while it is not
monolithic, it is both harder and much lighter than cob would be when
building the same structure.  This difference could be very dangerous
for cobbers during construction.

Shannon C. Dealy      |               DeaTech Research Inc.
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