[Cob] Rammed Cob

[Barbara Roemer & Glenn Miller]

Damon wrote:

"...as I was looking into rammed earth, I
thought a person could make forms and pack cob into them, right? It
seems like it would be more stable that rammed earth, from what I
know about it. There wouldn't be worry on the walls slumping and
lifts could be done higher. But, packing the cob mix may get rid of
the air pockets (isn't that why cob does so well in transferring heat?)."

Packed cob, even when very well-tamped, is not as stable as rammed earth
which is rammed pneumatically, with consideration for the soil type, and
usually with some small amount of cement stabilizing it.  It is packed into
forms, so can be as smooth sided as glass, as well.  But, formed up cob does
go up far faster, has less splooging, and can go up much higher in a lift
and in a day than regular cob.  It might have fewer air pockets, though if
you have pockets in regular cobbing, each new layer is not being worked well
enough into the old.  Cob doesn't so much transfer heat as store it in its
thermal mass to release on a long, slow cycle.  Cob radiates well to the
degree that it is solid - stone-like, not because it has air spaces in it.
It can be made more insulative with more straw, proportionately, and less
clay, which also lowers its thermal mass.


You might want to have a look at <californiacob.com> for a formed up house.
The technique includes straight and curved forms, and was devised by Simon
Holmes and Rob Pollacek, the latter whose house is featured on the site, and
written up by Rob for CobWeb, Cob Cottage's newsletter.

Regards,

Barbara, neighbor of Simon and Rob's