Cob: freezing walls

[Shannon C. Dealy]

On Sat, 3 May 2003, Brad Calvert wrote:
[snip]
> Can cob (or other forms of earth walls) be used in places where the
> temperature remains below freezing for long enough for the entire wall
> temperature to go below 0 deg C / 32 deg F?

Yes

> My guess is as long as day temperatures are reasonably well above freezing
> then the wall retains enough heat overnight to not get too cold.
[snip]
> My thoughts are that whatever moisture is in the wall freezes, expands and
> causes the wall to tear itself apart over repeated freezing/thawing cycles.

This is only an issue when the wall is being built and for a short period
of time afterwards while the water content of the wall is still fairly
high, once the wall has dried to a certain point, this is no longer an
issue.  Depending on your mix and the weather at the time you were
building, the cob could be safe from this problem in as little as a few
days time, or as long as many months (though the months range would be
mostly in very humid areas, or for people like me who are crazy enough to
build in winter :-)

> Has anyone tried cob in Canada?

Yes, quite a few people have without any problems of this sort.

I have only heard of one incident where a problem of this sort occurred,
it was during a cob workshop in Colorado and on the first night a
strong cold front moved through and dropped the temperatures down
sufficiently that the newly started wall froze and puffed up like
pop corn.  The next day they had to remove all the cob and start over,
though I believe the rest of the workshop went without any further
problems.

Shannon C. Dealy      |               DeaTech Research Inc.
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