Cob: Cob plaster on a conventional wall!

[Ocean]

I don't see any reason stucco mesh (lath) would degrade the strength of
the earthen plaster.  It's main purpose is to attach the plaster coat
to the sheathing.  And once it is dry, there isn't enough moisture to
rust the lath, which is by the way, galvanized (we've left the stuff in
the weather, lots of rain, for over a year, NO RUST!)  Also, we
attached the lath to the sheathing with roofing nails, which are also
galvanized.

And no, as I wrote in my first email, we didn't use any lime, just
seived clay, sand and chopped straw.  Again, this wall is protected
from direct weather, under a patio roof.  I wouldn't try this as an
exterior finish on a conventional house.  After all, if you've alread
got a wooden stud frame house, which not use wooden siding (or
aluminum?)

My response was to the question about using earthen plasters in
interior applications.  I don't see why we would want to use lime on
the interior either, unless it is an area where you want to wash the
wall or for the lighter color.  Like cement, lime (quick or hydrated)
is an industrial product which requires a lot of energy to produce. 
BTW, the earthen plastered wall is beautiful, the red clay giving the
wall a soft rust color.

Ocean

--- Darel Henman <henman at it.to-be.co.jp> wrote:
> Ocean,
>   I earnestly hope that you wall lives long.  But, I fear the use of
> a
> metal lath will shorten the life of the mud plaster wall.  
> 
>   Also if you are in a humid area, the metal lath, if it is not rust
> proof could rust through in time.  Mud plasters with have been aged
> with
> the straw until the straw ferments is reported to dry harder and last
> longer than simley added the chipped straw.
> 
>   One should even consider using rust proof nails to attach lath in
> humid areas or where walls will be subject to a lot of water vapor.
> 
>   Since it is done I hope the walls lasts long.  Please give the
> group
> updates every so often as the data would be valuable to all of us.
> 
>   Did you put any lime in the mud plaster?
> 
> Darel


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