Cob/Earthbags & passive solar

[M J Epko]

	I like earthbags. I like cob too. I like cob more than I like earthbags,
but I do like earthbags quite a bit. They're different things, not really
interchangeable in all ways. Compressed earth blocks are different than
adobes, but they're the same thing, right? Not really.

At 06:33 PM 11/14/98 EST, Otherfish at aol.com wrote:
>re deterioration potential comparison of earthbag vs cob:
>... the concern I expressed
>about the stability of this form of construction is that unless there is some
>form of stabilization in the earth mixture itself, if & when the bag
>eventually deteriorates then what is there to keep the earth still in the
>wall?

	The end "product" is basically big unstabilized adobe blocks, sort of.
Depends on the soil used. Joe Kennedy started taking to "dimpling" the tops
of the bags during the tamping process as a sort of keying mechanism - not
a mechanical bond, but an interlocking approach. I consider that to be a
mostly futile gesture, but that's just my opinion. (This was not for domes,
but for stemwalls for strawbale/cob/what-have-you.) I do think the barbed
wire (with big barbs, not the puny stuff) between courses helps
significantly, particularly for doing domes, as does using a good cohesive
soil in the first place. Otherwise, stabilize; if the earthbags are being
used to make domes, safety should rightly be a primary concern.

	Steve Kemble & Carol Escott of Sustainable Systems Support are building a
non-dome earthbag place on some island in the Caribbean. The photos are
lovely.

	Anyway, in damp climates, I think the concern of
deformation/disintegration-of-bags leading to failure is valid, despite the
safest-dome-shape-what-there-is corbel action. Mostly I'd worry about
deformation and collapse due to saturation as a result of inadequate
moisture-"proofing", rather than bag disintegration. I say that with the
understanding that the bags will last nigh on forever if protected from UV.

	I agree that monolithic cob is stronger, but I'd rather stand for long
periods in a dome made of earthbags than a dome made of traditional cob,
for precisely the differences of procedure detailed by knowledgeable and
respected Mr Fordice. (I meant that, it wasn't a slight.)

>at the first Blackrange Lodge colloquium we built a tamped foundation of
>plastic woven sandbags filled with some sort of a  pea gravel material
>(volcanic origin, i think) & this was the base of a combo of liechmem & cob
>walls - this seems like a good use so long as the bags are protected from UV
>deterioration

	That foundation is doing fine, BTW.

	The same UV-protection needed to prevent the pumice from spilling out of
those bags are what's needed to keep the earthbags of the superadobe
technique in good shape. If a pea-gravel/pumice bag-foundation experiences
bag deterioration and that stuff spills out (assuming it's above grade), a
whole structure can be compromised.

>altho I'm not sure it is such a good idea
>in seismically active locations

	A concern I share. But perhaps I haven't quite grasped all the nuances of
Khalili's work. (OK, it's likely that I haven't. OK, almost a certainty.
OK, I definitely haven't.)



   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Freewheeling autonomous speculation - Think!
      Personality #7 represents only itself.
    M J Epko - duckchow at mail2.greenbuilder.com
               Kingston, New Mexico
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       Each morning sees some task begin,
       Each evening sees it close;
       Something attempted, something done,
       Has earned a night's repose.
              - Henry Wadsworth Longfellow,
                   "The Village Blacksmith"