[Cob] waterproofing the bermed side

[Tys Sniffen]

Hey folks,

 

I'm putting in my stem wall for my cob house, and slightly 'berming' the
north side.  My bond beam is about 10 inches thick (high) and I'll be
building an urbanite stem wall above that; about 2 to 3 feet high on the
north side to reach above the soil.  

 

Of course I've already got the French drain in the trench underneath the
bond beam, and I'll be doing another perforated pipe in gravel along side
the wall, underground, and mostly back filling with gravel, but: I intend to
waterproof that portion of the wall that's underground. Suggestions?

 

I've heard about 'Bentonite', I was thinking about tar paper, I know there's
a number of (ugly, toxic) asphalt type things, from that silver roof paint
goo to other concrete waterproofing stuff. 

 

I'm trying to balance toxicity, with price, with ease of use, with
functionality.  Any experience out there?

 

Tys