[Cob] any ideas for building cob on a hill?

[Amanda Peck]

Sounds like where I'm sitting right now!  The travel trailer is sitting 
below the top of the circular driveway which is maybe 25 feet above (North 
of) me. And this is the least likely to flood, won't need a 40-foot bridge 
spot on my original 24 acres.  The opening to the septic tank (THAT was 
mildly sloped enough to put in the drain field!) gets covered with gravel 
all the time.

One of these years I may get around to building more or less what I 
originally designed in the way of a studio for here.

Unfortunately it involves swales uphill to give me drainage going the way I 
want it. Then a retaining wall (This needs to be checked out with an 
engineer!).   THEN I think that the uphill wall needs to be sunk into the 
hill, two-four feet.  Heavy duty drainage above the uphill retaining wall, 
then a draining space, then the building wall on top of a--sorry--concrete 
stem wall.

The trailer is actually sitting on both fill and cut where the driveway 
people made a level place for it (didn't need to BUY fill, just use what 
they'd cut out).  So I need to extend the level place out six or eight feet 
towards the dry wash to the south, heavy duty rock-filled baskets (which 
either are or are not called gabions, but "gabions" gives you the 
information when you run a search)  that work both for drainage and form, 
possibly with a hole for an underground water tank.  This is "talk to an 
engineer" time as well.  (The person who I contacted when I first moved here 
never came, and eventually went out of business.)

And even then I will end up with an oddly shaped trapezoidal building (hey, 
but there will be a nice little patio overlooking the dry wash!).

I went with Christopher Alexander's admonition to build where you can SEE 
the most beautiful place, not IN it.

For space--and time--reasons, I'm thinking compressed earth blocks, roof up 
first, build to it.  But it's going to need a lot of concrete in the 
foundations.  And LOTS of engineered drainage.

There has been someone on this list who was nuts about relieving hydraulic 
pressure.  Engineering walls so they both have both enough purchase back 
into the hill, AND enough drainage so that water pressure won't push it 
over.  That, not washing away, is your main concern.

You can see the problem in the bulges that railroad tie walls make if there 
are no deadmen (ties connected securely to the wall, but going perpendicular 
to it back into the hill) in the design.  The wire baskets stepped back seem 
to be doing fine so that the store below--WAY below--the Wal-Mart parking 
lot in Florence seems secure.

Here is one picture, heavily altered, of rock-filled baskets on the 
Tennessee river, the idea is to keep barge traffic and floods from dumping 
some indian mounds into the river. (Part of the Shiloh national park)

http://groups.msn.com/ap615/newpicturesmidsept2002.msnw?action=ShowPhoto&PhotoID=202

Here is a (straight, this time) picture of parking lot of the pet store 
below Walmart.  It's grown up so that steps the baskets make hardly show two 
years later.

http://groups.msn.com/ap615/spring2002.msnw?action=ShowPhoto&PhotoID=141

(The rest of my driveway?  Close onto level all the way out to the road on 
the downhill side!)

Oh, yes, and somebody built themselves a straw-bale vault using rock-filled 
baskets as their foundation.



.........
Greg McLeod writes:

There's a property that my wife and i really like but the problem is
that the only place to build on goes from 10 degree slope down for
about 20-25ft. Then it drops off on 30-40 degree slope down for
a long way.

My questions are:
how deep should one dig into the land to get a level
space versus using fill dirt to get a level space?

what precautions should be done to stablize the soil
downhill of the house so that it doesn't wash away,
taking our proposed beautiful cob house with it?