Cob Photos of famous FC domes

[M J Epko]

At 09:46 AM 9/16/98 -0500, you wrote:
>I looked at the photos.  They showed very interesting looking
>structures, but what was the cause of all the deterioration?

	Apparently moisture, and possibly deformation qualities of the material
itself. The collapsed domes shouldn't have collapsed; the blocks were
beveled on the vertical faces (didn't appear to be on the horizontal
faces), and that should have been sufficient to prevent them from falling
inward like they did. It appears that the material became saturated and
caved in. It was suggested to me that the builder of the smaller domes made
of the large "brownie blocks" thinks that the weight of the bottles in some
of the blocks contributed to the collapse; however, most of the collapsed
parts didn't have bottles in or near them. And if that were the case, that
also raises a concern about the ability of these particular domes - a dome
being an extremely strong shape - to handle snow loads, etc, if it can't
even handle a couple empty six-packs.

	Another apparent difficulty is that the material doesn't bond with itself.
The FC "mortar" used to "glue" the blocks together didn't penetrate or
adhere to the blocks. All the surfaces were smooth and fully separate, and
it looked like the only thing holding the structures together was gravity.
This nonadhesion was also displayed in those photos showing large sections
of the FC "stucco" peeling away from the structures.

	I didn't notice any UV degradation (except on the poly bags used as forms
for the small bricks), but then there wasn't any FC material that might
have been UV protected lying around to compare. There was most assuredly
significant shrinkage. One of the photos I didn't scan shows the bricks in
a matrix of the FC mortar which ended up as brick-air-mortar-air-brick;
other photos show significant shrinkage fissures, particularly at (but by
no means limited to) cold joints, and where the material was applied wet.

>Has "FC" been improved since these structures were built?

	Um, these aren't old structures... comparatively, they're brand new.
Months. It appears that FC was improved well before these structures were
built, and the modifications they implemented for these structures
(primarily adding sand to the mix, and employing sloppy & incomplete
workmanship) weren't improvements at all. I found it telling that the only
structure which appears to be sound out there has a foundation, vertical
walls, and a roof.

>Is the moral of the story that we should avoid using "FC"?

	I think the moral is to avoid that mix and that use of FC. Eric
Patterson's FC dome is still sound after almost six years in the Silver
City, NM, climate. That's not to say that it would work as well in another
climate. That building used a different material, and a different method of
construction. His privacy and garden walls do appear sound, as does a
poured monolithic privacy wall in another part of the town. The FC addition
to his home is dry, comfortable and beautiful.

	It's been my contention that FC as it was popularly promoted recently is
dangerous, and I really ticked some people off (without trying to) by
saying so. I do think the idea has promise, but it - like ANY method or
material - has to be looked at with a very critical eye. There are people
experimenting with different mixtures and applications, and I know that
they're being more cautious and thorough about what they're doing to avoid
going off half-cocked. Some of that work may yield acceptably safe and
well-performing materials and methods.



   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Freewheeling autonomous speculation - Think!
      Personality #7 represents only itself.
    M J Epko - duckchow at mail2.greenbuilder.com
               Kingston, New Mexico
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 It is your concern when the wall next door is on fire.
                                     - Horace, Epistles