[Cob] Re: Foundations

[Barbara Roemer]

I must be missing something in the current discussion of foundations.  I
don't want any water to move through my foundations (I'd bet that Falling
Water overhangs the stream, and that the foundations were very well
protected from its water) even if it were all concrete, since concrete wicks
moisture up eight stories.  Water moving through the soil is the primary
means by which the soil beneath and surrounding your structure is cooled,
and therefore cools your home (not to speak of erosion and undermining).
Keeping that soil,  your foundations, and your walls dry will make your home
much more comfortable and last longer, and do it with far less cost for
heating than damp soil.  So I think drainage is imperative, both in the
bottom of the trench, and out from it if you have slope or moving water or
both.

Of rubble trenches, my understanding is that the rubble replaces some of the
concrete, but that the foundation still needs to be sound, and whatever
replacement elements you use need to be bound with concrete: it supports the
walls, excludes critters and water, and in heating climates, keeps out the
cold, to one degree or another.  To those ends, it's not advisable to use
river stone since it doesn't lock together when it's compacted.  Crushed
sharp stone is what you want.  For foils who want more definitive answers
about how to do a rubble trench foundation, there's a short article and a
great drawing in the wonderful book, "The Art of Natural Building" by Joseph
Kennedy, Michael Smith (yep, of cob wonders), and I think Dan Chiras.  The
particular article is written by Canadian Rob Tom, the list mom on the Yahoo
straw bale list, and an expert on RT Foundations.  We used it on our straw
bale powerhouse, and have seen it used in Northern California on many sites,
both with cob and bale.

And if you want to really make your house independent of heating sources,
give it a good solar siting and investigate the Annualized Geo-Solar system
for excluding water from an umbrella around and under your house, and
insulating it so the whole area serves as a heat sink for the summer's hot
air.  It works like a thermal flywheel, releasing that heat during the cold
season just where you need it, and at a rate that will last through the
winter until you have natural solar heating again.  You can find info on AGS
at Don Stephens' site ( <www.greenershelter.com>  ), and a frequent
discussion of it on the organic architecture list from natural builders who
are using the system.