Rethink Your Life!
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The Work of Art and The Art of Work
Kiko Denzer on Art

[Cob] Light Clay OPTIONS- vs mold- baled- pressed

Charmaine Taylor dirtcheapbuilderbooks at
Tue Dec 30 14:46:54 CST 2008

  Don Jackson ASKED:
3.  If "light clay" was tightly compressed and covered with earth
plaster, could it ever mold?
 Azalea, OR

Don- people add various   agents to prevent mold.. clay by itself will
not mold, but any buggies and food/grain from the straw will cause
growth,  so I always add hydrated lime ( just  plain bagged lime @
$9.a  50 lb sack, even as little as 2% will prevent cracking  of clay
and inhibit mold and help fireproof the material.  give yourself that
extra edge and add either powdered lime to the clay mix before dipping
straw, OR add lime water to the clay to make the slip.. it will "seize
up" a bit and become more milkshake like, once the straw is tossed and
thoroughly damped and allowed to be coated, the lime will deter growth
of anything.  a simple lime wash over the final  stuffed walls is
another boost to mold and fire resistance.

I have a small  100+ year old horse barn being converted to my work studio.
  I have  used readily available redwood sawdust, but have infilled
the  timber walls with both woodchip clay,  sawdust, rice   hulls and
other paper shredded  (paperaqdobe) materials.  Each has clay and lime
as the binder. I have cast blocks to fit the stud space, and let cure
in the sun like adobes do. and also poured in a thick  infill with a
form board, cardboard, pegboard, fabric netting, burlap and other
"wall" material to keep it in place over the wet mix while it cures.
all these things work..  use whatcha got!   after one wall dried I
took off the board we  used to  form it, and   stapled clay-dipped
cheesecloth across the studs, this gave me the option to directly
plaster  over  the clay/sawdust mix.  This plaster was a first and
leveling coat, the next was a lime and paper plaster that turned back
to a limestone, literally fireproof wall.   no excess wood or metal or
anything else was required.  once the clay straw or sawdust clay mix
dries you have a hard block that is insulating and staying put.  don't
 press too much as you do loose air pockets and R value.

light straw is SUPPOSED ( as attested by a builder in N. Cal.)  to be
as high as R 22-25 for a 12" wall.. I am not sure I trust that, but it
gives a good range at least to reach R19.

Ms. Charmaine  Taylor/ Taylor Publishing
Toll Free Order: 1-888-441-1632   www.
PO Box 375, Cutten CA 95534