[Cob] Newbie w/ Questions about 1st project

[Amanda Peck]

Australians and those who read a lot of British mysteries both occasionally 
use British language.

You could look up "stem-wall" as well.  From the beginning the straw bale 
revival people have highly recommended a stem-wall to keep your straw off 
the ground--outside--AND the floor--inside, so that some sort of 
disaster--leak in the washing machine, somebody forgot they'd started 
filling the tub for a bath, tree comes down on part of the roof, etc., 
doesn't do unfixable things to your walls--six inches (or more) are 
recommended for inside.

The "rubble trench foundation" probably works best on some kind of slope.  
Dig a nice big trench--maybe not much wider than your walls, and variably 
recommended as to depth.  I've seen both "to frost depth" and "you don't 
need that much because you've got a drain."  In the bottom of the trench put 
a bit of gravel, a bunch of those drain sticks with the big holes on the 
top, run the whole mess downward all the way to daylight. Then, fill the 
trench with really well tamped--one local person recommended fairly small 
gravel--it just about rings when it's right.   If you're really on a slope a 
swale or even two--with or without gravel and more drains again to daylight 
in them--farther up the hill.  Water right around the house is bad stuff, no 
matter how you are building.

There's also something very similar called the "insulated frost-free 
foundation."  Somewhere around the same thing with insulation in the ground, 
or possibly angled out to protect the ground right by the house from 
freezing.

Then, at or just about to ground level, start your stem-wall.  Recommended 
at least a foot, more likely a foot and a half.  Whatever--nice and 
green--urbanite (broken up concrete), local stone, or easier to get someone 
to do this for you--concrete block.  This does need to support the width of 
the bottom of the wall.

Between both the rubble trench foundation (Frank Lloyd Wright used these, 
they worked a lot better than his roofs) and the stemwall you may have 
enough drainage/spacing that you can avoid vapor barriers.  But we're 
talking about a layer or two of tarpaper here, with holes so that rebar or 
something could go from the stem-wall into the cob or straw.  Conceivably 
aluminum flashing (although that might be iffy if you were putting it onto a 
rough stone wall).

Remember that if you were building a 2x4 stick house somewhere you would get 
to start with a wall because you wouldn't want to have soil--termite-bearing 
dirt--within about 18" of your wood.

Both cob and straw-bale do exist happily in quite damp areas.  Down in a 
dark hollow (where the sun refuse to shine!--I've got them, even if I'm not 
planning to build in one) or deep in the woods with overhanging dripping 
trees may make a difference.  I'm thinking I want not much in the way of 
steps into the house, but there are straw bale and presumably cob houses 
built over crawl-spaces or  basements.

...........................
Kathy wrote (snipped)

 >
 > I didn't see mention of a dampcourse between your stones and first layer 
of
 > cob. This is critical to stop rising damp.
  > Lance
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I've chosen NOT to use anything to prevent the water from rising through my 
wall because what ya put in there to stop water rising ALSO prevents water 
that does get in from drying out.

....

I'm sort of doubtful at this stage if COB is going to be a good material for 
me to use in my particular site (despite reading all the assurances of many 
sites which claim all ya need to make cob feasible in damp climates are good 
"hats and boots" approach & lime plasters).

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