Cob: Flooding questions

[Shannon C. Dealy]

On Fri, 22 Aug 2003, R M wrote:

[snip]
> I have two questions:
> Would standing water for several hours be enough to collapse the walls
> of a cob home?

Normally, the cob should be able to handle several hours or even a full
day of contact without problems, however, if the cob is not fully dried,
it will significantly shorten the amount of time it can withstand direct
contact with standing water, the greater the moisture content of the cob,
the faster it will absorb additional water.  Your cob mixture can also
make quite a bit of difference, I have seen significant variation in the
rate at which dried cob will absorb water on building projects with
different soil compositions and sand/clay ratios in the mix.

> How cautious should you be with building?  I suppose a stemwall several
> feet high would definitely protect from this kind of situation, but is
> it worth the extra work when you have no reason to expect to need it?
> How paranoid should you be when planning for eventualities?

It kind of depends on your needs and concerns, though the high stem wall
has the added benefit of preventing surface errosion of cob at the base of
the wall due to rain splash, as well as being the generally recommended
practice for cob (not that I ever follow this practice :-)

Shannon C. Dealy      |               DeaTech Research Inc.
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