[Cob] Coblist Digest, Vol 6, Issue 173

[Bernhard Masterson]

Greetings Dirk,
   I live in wet Portland, OR and regularly do work with the Village Building Convergence where many cob benches have been built in the city.  Originally cobbers were optimistic that a good oil and waxing would preserve the benches.  Over the course of the last eight years that optimism has changed and now any bench that is expected to last is built with a roof.  The biggest problem is that eventually uncovered cob gets wet, no matter what the treatment and then when it freezes the expansion of the ice breaks large chunks off the surface.  Once saturated the straw eventually rots and then the tensile strength of cob is mostly gone.  Surface treatments have included, beeswax and linseed oil, latex paint, lime, and concrete stucco (the most successful).  One material not yet tried is a polyurethane varnish.  When building benches outside be sure to build in such a way that there is NO puddling on the surface, even if the bench is covered.  Another option is to build a curved, sculpted wall with deadman embedded and then use wooden slats as a bench surface.  This is actually warmer to sit on and building a narrow shake roof over the wall is easy to do.

Happy cobbing,
- Bernhard 


____________________________________bernhard_masterson at hotmail.com

Natural building instruction and consultation



> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Tue, 16 Dec 2008 13:45:51 -0800 (PST)
> From: Terra Incognita <nomadbuzzahd at yahoo.com>
> Subject: [Cob] Weatherproofing a cob bench
> 
> Hi there,
> 
> I finished building a cob bench in Ithaca, New York this summer and wasn't quite sure how to weather proof it after applying a clay plaster. It looked great and I knew it was something of a gamble but I had to leave town and figured I'd just let it's exposure be an experiment. There's no roof over the bench and it's not realistic to build one. The rain this fall eroded patches of the plaster and I intend to spruce it up come springtime. Currently, I have a tarp over it. 
> 
> What are my options to keep this bench safe in the elements if a roof is not an option? I've seen uncovered cob benches elsewhere. Is a lime plaster my best bet or are there other options?
> 
> Thanks much,
> 
> Dirk Trachy
> Ithaca Freeskool
> http://www.ithacafreeskool.wordpress.com
> 
> 
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