Cob: Concrete, reduce, reuse, eliminate!

[David Knapp]

----- Original Message -----
From: Sojourner <sojournr at missouri.org>
To: coblist <coblist at deatech.com>
Sent: Saturday, July 17, 1999 2:17 PM
Subject: Re: Cob:Insulation & papercrete-bad idea


> Well, other than to say you don't like the thought, you give no reason
> why you think papercrete and cob is a "bad idea".
>
> So going from there -
>
> crtaylor wrote:
> >
> Lumber, adobe mixes, sand, gravel - all of these building materials
> nearly always have to be harvested/mined from SOMEWHERE, and trucked to
> where ever you are using them.  Concrete's no worse, IMO.  In fact, from
> the standpoint of longevity of the building, a concrete building that
> lasts virtually forever actually could be said to leave a smaller
> footprint on the earth's ecology - as opposed to the current fad for
> stick-frame buildings that are often decrepit and require extensive
> repairs in 20 or 30 years, and are usually a lost cause in less than 50.

Unfortunately, concrete lasting forever hasn't been invented yet.  Concrete
in the present form we know it was inverted just after WW2 and our landfills
contain many mega tons of the stuff.  The earlier forms of it were even less
durable.  One of the longest lasting example is the great pyramids, where
the mixture used was more of a mineral and boiled cactus (as a binder)
content.  From several of the weekend workshops I attended, we learned that
environmental load of concrete is something on the order of a thousand
years.  We have barely covered fifty years of concrete in its present form
for foundations and it seems to be doing only slightly better than limestone
(fortunately concrete is easier to apply water proofing to, which wouldn't
be as necessary had builders been competent is designing in French drains
automatically from the beginning -- which helps limestone foundations
immensely too).  The mining, processing, and shipping of concrete are
actually a lot worse than what you mentioned because of the EXTREME amount
of heating required in the manufacturing process.  This gives it a magnitude
increase on the "HIT-O" meter of environmental meltdown scale.

Now I know that concrete is very handy to use and it works great for capping
off rubble trench foundations and as bond beams.  In fact, many local
building codes specifically require it in many foundations.  But as cob and
straw bale owner-builders, we can use it just where ever we have to, to
lesson the impact from it.  I agree with you it is ugly and none of it will
ever be exposed for all to see in my future home.

The problem with trying to make a concrete building last a thousand years is
that we have no control over those who will come after us, trash it, and
send it to the land fill.  Any time WE choose to use a building product, WE
are responsible for it long afterwards in this case.  So if you choose to
build with just cob, it can be recycled and used again.  Concrete can too,
especially as a rubble infill ... but too often it is just landfilled.  Then
the environmental hit goes back to the poor smuck that choose to use it in
the first place as well as the bone heads who were making way for "NEW"
concrete to be used.

There is ANOTHER reason for severely limiting our use of concrete.  While
many, many groups and organizations try to seal out and positively ventilate
around, RADON gas is in many cases is actually produced by radioactive decay
of the rock inside the concrete itself.  Since concrete is actually a very
porous material, it is nearly impossible to eliminate it from seeping out
radon gas.  As a Band-Aid fix in my twenty year old stickbuilt ranch house
(that soon some other poor smuck will own as we start to build our cob/SB
home), we have to run an air-to-air heat ventilator to exhaust the radon
build up.  Many thousands of homes have this problem, especially "tight"
homes.  A cob (and SB home with lots of added thermal mass) home doesn't
need to be tight and this helps reduce any radon buildup potential quite a
bit.

And the final thing I'd like to say about concrete really makes me sick.
You've heard about companies dumping their toxic leftovers into commercial
fossil fuel based fertilizers as fillers?  Yeah, they do that because the
leftovers are almost impossible to dispose of safely and cost effectively.
Well, we learned at a recent hands-on workshop that companies have been
doing this to concrete for many. many years and not telling us.  There is a
certain percentage of fill and contaminants that are allowed and your local
concrete operator may not even be aware of it because they are chiefly
concerned with baking their cakes and getting them to market as soon as they
can.  This is very sickening and is typical of what happens when the
consumer is not baby sitting every step of every process where greed and
profit are the main determiners of business.  No wonder why childhood
cancers and diseases seem to linger on through the generations.

So just like I have to grow my own vegetables with my own two hands to
insure I am eating safe food, I now have great motivations for reducing or
trying to eliminate as much concrete as possible in my building projects.
Even building cob, it certainly would be worth while to know where any of
your imported clay or sand is coming from too.  Unless you have been there
to baby-sit every step in the process, you could be allowing the interests
of business dictate what your quality of life will be.

Dave Knapp
Winnebago, Illinois