Cob Re: Work in Georgia last weekend

[Will Firstbrook WCB of BC]

Hi Pat,

Thanks for the update and sharing your design ideas. Sounds like your
dome is quite an undertaking and I wish you the best.  I have some
questions regarding your dome.  My understanding is the completed top
section of the dome would consist of the following materials in order
from top to bottom:

cement
tar paper
straw clay (liechtlehmbau)
cement
carpet
oak saplings
lime earth plaster

Your method & materials sounds quite reasonable. I wonder if
condensation is a potential problem due to the widely differing rates of
breathability of your materials. Like the adobe buildings that were
plastered with cement that created a vapor barrier that caused the adobe
walls to deteriorate. I have no idea if this is a problem in this case,
that is why I'm asking. If there is a potential problem do you have any
ideas to deal with the problem? I wonder if there is a cheep Gore-Tex
type cement that allows vapor to pass but not water. Perhaps air vents
in the cement that go upward from outside to inside so no rain can enter
but allow trapped moisture to escape.
 
I am also interested in a much smaller scaled dome so I am very
interested in your ideas and experiences. 

Regards,
Will