[Cob] foundation rock type

[Amanda Peck]

1) how nice, I had to buy clay, harder to find than sand!

Look up rubble trench foundation.  If anyone in your area is using it, they 
would know how wide, how far down.  In general, a bit wider than your wall.  
Here, a foot above the drain is apparently OK, but we don't have the weather 
extremes that parts of Texas have.

2) You need perforated drain around (under) the foundation/footings, with 
the holes facing up (Not the septic tank stuff with holes all around).  It 
needs to slope from a high point all the way to daylight!  So your footings 
will not be the same height all the way around.  It may be a good idea to 
insulate the outside of your rubble trench.   Someone here who has done this 
before told me small, clean rock, packed to the point that it rings.  
Another someone (somewhat less reliable than the first, I'm afraid) said 
that sleeves and sand were more trouble than they are worth.

And after that, a mortared foundation to raise the cob off the ground 
"enough" so it won't get or stay wet.

If water is sweeping down the hill towards the house, either a second drain 
a few feet away, and/or take a look at Toby Hemenway's book (Gaia's Garden) 
for information on swales.

3) I don't know anything about honeycomb rock.  (amazing, and I can't even 
make anything up!)  Ask the locals.

4) Overhangs are sized for shade in the worst of the summer, sun in the 
coldest of the winter.  There will be a lot of in-between times.  I had only 
slightly thought about this for me, thought pretty full sun 
November-February.  Which would give me May-August with no sun around the 
middle of the day.

Friends with a passive solar house near here have a pergola with vines in 
the summer, AND a greenhouse than can be mostly opened, AND an awning all on 
their fairly long south side.  They are built into the hill with next to no 
insulation on the soil side (slip-formed concrete wall), and they do 
sometimes have to use a small window AC--110v--unit in the summer, mostly, 
they say, for humidity.  It works very nicely.

Another couple who modeled their house on that one, is, at least at first 
having to run a generator to run the AC so that they can get their house 
dried out as they are moving in, hoping that they hadn't hit a wet-weather 
spring on the back wall.  Since the house was open for a couple of years as 
they worked on it, it's possible that this is going to work.


..................

Hi-dee-ho everyone.

We are busy over here preparing land and house site... questions:

1. Our "soil" is almost entirely clay - on all 10 acres. How does this 
affect (if at all) the foundation, since clay expands and shrinks with the 
rain.

2. What is the best way to make drainage take the water away from the house, 
as the land has very little slope to it. I did read the books, but still not 
sure.

3. There are many rocks, of various sizes a fist size to the size of a bed 
pillow. They are called honeycomb rocks and look like swiss cheese. Can 
these be used for the foundation? Do I need to fill in the holes with cement 
or something? Suggestions?

4. Our home site is in Texas - hot during the summer. How does this affect 
the southern facing windows? Do I just rely on the roof overhangs? Or a 
porch or trellis overhead? Or do I angle it so I am not dead on facing 
south?

Thanks everyone!

Jill & gang

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