Cob: House plans/living roof

[Waiting4 TheDay]

Hello,

Been lurking on the list for quite awhile, but have yet to see my particular 
problem(s) addressed.  I am building a 20' inside diameter round cob house 
with a clerestory living roof system.  The circle will be split by a cob 
wall running east/west the the diameter of the house.  The base of this wall 
will be 24", while the base of the curved outside walls will be 18".  All 
walls will be load-bearing.  I've cut 12" diameter timbers to span the 
(maximum) 10' length from the inside wall to the outside.  Now for the 
issues...

I intend to use a rubble trench system for the foundation.  Rather than 
build a stemwall of expensive material (block, rock, concrete), I have 
access to a large number of incredibly sturdy plastic soda cases with solid 
quarter-inch sides.  The idea is to fill these with gravel and use them as 
blocks, thus providing a moisture break.  Stakes can be driven through them 
to secure them to the gravel in the trench, and flashing can be used to 
secure them to each other.  As an outside covering, I envision using a thin 
coat of concrete/fiberglass slurry sold in a bucket.  (I don't want to use 
this or the aluminum flashing or the pond liner for the roof, but can see no 
long-term, working alternatives.)  Here's the question:  I plan on having 
12" of cob on the gravel in the soda case, while the other 6" will be 
resting on the gravel that will underlay the cob floor.  Is this a problem?  
I can't find any reference to this situation anyplace (and I've read Ianto 
Evans' "Hand-Sculpted House" twice).

Next issue is the living roof.  Evans does deal with it some, as does Rob 
Roy.  The problem I'm having tho' is with the design of the fascia and how 
the water drains.  Evans states that the waterproof layer goes over the 
fascia, yet his diagram in the book doesn't show that.  And everyone says 
that the waterproofing should be covered to avoid degradation from UV, but 
if it runs over the fascia it will be exposed to the elements. Besides the 
obvious, my question is would a fascia even be necessary if the slope of the 
roof were shallow enough to prevent erosion and you had plants aggressive 
enough to hold the soil in place?  (BTW, I'm a nurseryman, and there are two 
genus that, in my mind, would work wonderfully on a living roof: the mints 
and the bellflowers (specifically Campanula rapunculoides and C. punctata)).

That's it for now, but as things continue/evolve, I'm sure I'll post more 
questions.  Thanks for any insight.

Chuck





_________________________________________________________________
The new MSN 8: smart spam protection and 2 months FREE*  
http://join.msn.com/?page=features/junkmail