Cob roofing?

[cobcrew at sprynet.com]

On Tue, 25 Nov 1997, "GENTH, APRIL" <alg5866 at sru.edu> wrote:
>        I've heard of earthen roofing.  To prevent the devastating fires
>possible with thatch rooves, could a network of wooden planks with light
>bricks of mud laid ontop of them work, like wattle and daub structures do?
>Add to this a thin layer of mud on top and then thatching on top of that?
>Would this approach cause too much stress of weight on the wood planking?
>Too much work? Implausible?
>
We are about to try a cob roof (end of January).  It will be on a circular, 
15.5' diameter structure.  The plan is to use a catenary curve with an 
eventual "bee-hive" shape, with a opening at the top.  We'll use a bond 
beam with bamboo curved to the top and bamboo cross members to make a frame 
to support the wet cob.  When the cob dries, we hope the bamboo will no 
longer be structural, as we've heard that it has a 20-30 year life.  (Have 
been warned against rebar embedded in cob).  Outer coatings will be a 
lime-based plaster with a breathable sealant on top.  If that isn't enough, 
we'll try ceramic tiles.
(This is being done near Austin, TX as part of a 1200 sq. ft. (outer 
measurement) house.)  The walls are 22" thick at the base.
Haven't checked the archives of this mail list yet for any other 
information on this - have you? 
Nobody wants us to do this - "you're all gonna die" is the general 
consensus.  But this is a small utility building; we're not going to let 
what happened in Northern California years ago (under different conditions) 
deter us.  

Mike Carter, Carol Cannon.