[Cob] foundation

[Lisa Winter]

Hi all,
was hoping i could get some suggestions.  my husband
and i are getting ready to start our cob house this
spring.  But we are having a hard time deciding what
to use for foundation.  we are going to dig a trench
and then fill it with a drainage pipe and then gravel.
 but we're having a hard time deciding how to build up
the foundation tall enough to do our cob building.  we
were thinking about using large rocks, there is a
quarry near and we think we could get the rocks easily
but are not sure how uniform they will be or what size
and if we would need to cement them together.  we've
also discussed using old concrete from like sidewalks
(it has a name- which of course escapes me at the
moment).  you can get it from the city dump - but
we're not sure how in the world we could get enough of
it back to our building site and we used some last
year to build a cob stove, but the pieces are really
unpredictable in size and shape.  we've also discussed
using poured concrete, but i think that having to
build forms and such sounds wasteful.  could you use
that wood over again, like for the roof or something. 
anyway, i guess i'm just asking for some suggestions
and to see what other people have used for foundation
and how that experience was for them. 
thanks,
lisa and john