[Cob] Tires For a Foundation?

[Amanda Peck]

Putting filled tires, or something, under the whole house can be a pretty 
good idea.  In that case simply filling around them can work just fine.  An 
internet acquaintance did something very like this for his house, although 
he did pour a slab, and a block or concrete foundation.  Not an "all 
natural" building.

A foundation is for me the foundation for the very heavy WALLS.  And here 
you really want to have a solid level surface for the wall to stand on.   
Becky Bee's diagram looks like it might be only five or six inches over 
ground level.  That could be one tire high, if you could just set them on 
flat level ground.  Most everybody else would use at least three layers on 
level ground--one layer with the top level with the ground, drains to 
daylight underneath or beside, two more to raise the house a bit in case of 
flood or whatever.

You also want a solid surface to work from.  On that gabion foundation house 
I understand everyone cried because of barked shins because the gabions were 
outside of the wall area, a big step up.  They may have gotten used to it, 
but....  Having to step up and down as you moved around the house plastering 
would be worse, I'd think.

Two circles meet at a point, not a line. With cob you've got 15-20 inches 
width that has to stay up.  I wouldn't think that fairly loose gravel would 
work, tamping sideways isn't going to help.  Cobbing down to the ground 
between the arcs of the tires would, but that has its own problems--like 
water--standing, running, rain, windblown--all the reasons you use a 
stemwall to start with.

Of course you could use big tires, and then make the wall scallop across 
following the edges, with attention to the inside of the foundation--other 
tires and the spaces between them filled, or the whole inside filled with 
very well tamped rock/caliche.  It would make a very strong wall, I'd think.

On steps or retaining walls built of tires, it's easy enough to step the 
tires back so that the outside edge of the upper tire is resting on the dot 
that connects the circles, and the upper tire is sitting on the original 
dirt or on gravel for drainage.  But I think it would be really awkward 
working on a building when in order to add cob to the wall, and plaster, and 
work on the roof you have to look down and see exactly where you are 
stepping, and positioning ladders might be really a pain.

Filling tires with tops on them takes a long time if you are not 
experienced, by the way,  and seemingly infinite amounts of fill dirt.  They 
expand almost like an innertube.  One try showed me that I really wanted 
topless tires.  I periodically have to refill and tamp my topless tires.

...................
Beno wrote:
What my idea was is to simply backfill the area inside the circle with 
rammed gravel. Your idea of cutting off the tops of the tires is a good one. 
That makes them easier to ram AND easier to screw together. If necessary, 
we'll screw them to a circle of tires behind the main circle to cut down any 
movement. Then I believe the whole foundation would be stable. And thanks 
for the links!

As I re-think this, perhaps a row of tires behind isn't necessary. Perhaps 
rebar rammed into the earth in front of and inside-behind the tires would be 
sufficient. Thoughts?
beno