Cob/Earth berming the "test module"

[Don Stephens]

On Wed, 1 Jul 1998, Deborah Harmes wrote:
> Don, My husband and I are exTREMEly interested in the concept of earth
> berming with a cob house.  In the prototype house that you mentioned, did
> you wrap the straw bales with the plastic and then cob over the walls that
> were earth bermed?  We weren't sure if cob would start to "soften" from
> repeated potential exposure to moist soil, although we had hoped that an
> adequate drainage field surrounding the house would solve that problem.
 
Deborah, good luck on your return to Tennessee.  The cob incorporated in
the module was the inside finish on the rammed-tire wall areas (we left
one spot open to show the tires) and seems to be doing fine.  But it is
important to remenber that the entire structure and the surrounding berms
out 10' to 20' are sloped to drain away and subsurface-membrained.  Also
there is airflow in and out of the structure continuously through the
in/out tubes to the solar thermosyphon. 

I would not recommend cob where it could wick up moisture.  The "bibles" 
of cob do a good job of explaining the importance and how tos of providing
capilary breaks for cob and know far more about this one material than I
may ever learn.  I do think that it would be worthwhile to try cob
subgrade, below the lateral insulation level, as a structural wall, with
some bamboo reinforcement, an outside vapor barrier (applied after the cob
had completed its initial drying process) and inside finishes that were
very breathable.  But, as I'm sure is the case with all us ecobuilding
pioneers, ideas flow much faster than the time to try/test them all.  If
you'd like to try this approach, feel free to call on me for assistance.
Since you're still in Washington (somewhere), you might want to stop over
this way and take a look-see at the module and the house following in its
"footingsteps" for yourselves.  ...Don

PS: a copy of the report and sketches might help you visualize what we
were/are studying with this particular test structure.  All I need is a
go-ahead to dump 12K on your email and a fax # for the sketches : }