Cob Curious

[Grace Benjamin]

Hello everyone;

I've been on this list for a while, but rarely posted; well now I have 
something to ask about...  I'm drawing up some plans for a cob/strawbale 
house.  Two story, in southern New England (eastern Conn. to be specific.)  
I'm aiming to cut costs, recycle as much as possible, build sustainably, and 
drastically minimize my electrical usage- or at least convert as much to 
solar power as possible.  I have some questions, some on foundations, and 
some on design.

First; foundations.  I don't think I want a basement, while I have a 
nostalgia for basements (the house I grew up in had one, and so on..) I'm 
not sure I'm up to the expense and labor involved.  Is anyone aware of how 
basements were put in before we poured concrete, and excavated with 
backhoes?  Because frankly, if I could get around the expense of a concrete 
contractor/major excavation, and the labor was not too terribly skilled- I 
would go for a basement.  In lieu of that- I have this idea.  Around the 
perimeter of the house, I would dig 3ft wide holes down below the freeze 
line, and then pour a concrete pier extending 3ft above grade.  In between 
the piers, I would lay a 3ft wide 'stone' wall made from salvaged concrete 
slabs over 4in of aggregate in a shallow trench:

Cutaway view from above-

                      interior of
                          wall
[=====]=================[=====]=================[=====]
[pier ]                 [pier ]                 [pier ]
[     ] 'stone' wall    [     ]  'stone' wall   [     ]
[=====]=================[=====]=================[=====]
                      exterior of
                          wall

Cutaway view from side-


|                             || <- Protective Lime based
|                             ||    plaster for exterior
|                             ||
|                             ||
|            cob              ||
|                             ||
|                             ||
|                             ||
|                             ||
|=============================||
|        Bond Beam            ||
|^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^|
|                              | ->Stone Wall
|         <- 3ft ->            |
|                              | ================> grade level
00000000000000000000000000000000 ->4in of aggregate

(not at all to scale!)

I would then tie the whole wall and pier structure together with a single 
concrete bond beam, poured both over the wall and the piers.  The cob walls 
would then sit on top of the bond beam.  Does this seem like a sound plan?  
Can anyone suggest improvements to the plan?


Second; design.  I have this notion of "whole-house" design, where the house 
is a machine, and with proper maintenance could theoreticaly last 
forever...but anyway- the total plan encompasses a solar green house 
attached to the first floor, with vents to draw in the warm air.  The first 
floor will be cob for thermal heat retention, and the second floor Straw 
Bale for insulative heat retention.  The greenhouse will also function as a 
summer kitchen (solar stove) to avoid heat accumulation in the main living 
space.  New England is rather pleasant in the summer with cooler night 
temperatures, so I'm not too concerned about cooling, just not getting hot.  
So my question is what moisture concerns should I expect vis-a-vis the 
greenhouse attached to the outside of a cob structure?  Has this been done 
anywhere, and how is it fairing?  I'm thinking that the the foundation I've 
mentioned should have no difficulty in supporting a second story made from 
SB, does that seem accurate?  Also, in this configuration, will I be able to 
construct a roof overhang wide enough to protect the cob first floor?  I'm 
also having an internal debate over the flooring for the first floor- I'd 
like to do some in floor radiant heating where I have coils full of water, 
being heated by running through the wall next to the hearth, imbedded in the 
floor throughout the first floor.  How much would something like that 
degrade the integrity of a cob wall, and would it be a practical application 
for an earthen floor in Southern N England?  Okay, I'm pretty much done for 
the moment, let me know what you all think.  Thanks much.

Grace


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