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Kiko Denzer on Art

[Cob] Curved bond beams

Tim Nam tkn317071 at
Fri Sep 26 01:06:00 CDT 2008

My suggestion would be to just make a few more cuts, at whatever angle feels right (and is easier to make) around your curves and have a polygon shaped top plate/bond beam, with gusseted joints, deadman anchored to the cob, or perhaps simply nail anchored, as in using old nails and such to give the cob something to grab. That is, assuming you have a bunch of salvaged lumber that needs to be used up creatively.  
 ...Not really sure if a top plate is absolutely necessary if the rafters are embedded in cob. The test building in that UBC earthquake/cob experiment had a shed roof with continuous rafters, I believe, and the roof didn't collapse, even in a simulated 9.0. Ziggy didn't use a top plate for his reciprocal roof, but he's not in a seismic area, either. But as I understand it, an earthquake can be a wave like motion on the surface of the land, iow, up and down and/or lateral shifting, side to side. All things being equal, I'm not sure how much more earthquake protection you get with a top plate. The cob is gonna hold it up either way.

What are you doing in Iraq?


----- Original Message ----
From: Mitch Ventura <h_anpyp at>
To: coblist at
Sent: Thursday, September 25, 2008 12:44:45 PM
Subject: [Cob] Curved bond beams

Just bought 5 hectares of land in Mexico and hope to build my cob home near the end of 2010, which gives me plenty of lead time for the planning. (Due to prior experience, I am a firm believer in "measure twice, cut once".)
My preference is to use solid wooden beams for the bond beam (live in a seismic area), but I also want to make a house that is curved; obviously straight wooden beams do not line-up well on bends.
How would one best make a bond beam on the top of a curved wall without having to resort to reinforced cement (or is that the only viable and proven option)?
Saludos from Iraq.
Mitch Ventura

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