# Cob mix formula



## Big Dave (Feb 5, 2006)

I am trying to find out about cob plaster. I think that is what it is called. You mix straw and clay and some type of lime. What type of lime? How much clay? How much straw? It is used a lot in perma culture I believe. Thanks for any input.


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## dirtman (Sep 15, 2011)

Probably hydrated lime. That's what we use for stucco. It's available at any farm supply and most concrete block dealers.


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## Big Dave (Feb 5, 2006)

Thanks for the info I will ask and hopefully not look dumb about it. More research to be done.


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## 45n5 (Jun 9, 2008)

cob plaster or "earthen plaster" doesn't usually (but can) have lime in it check out this link

Clay Plaster | Earth Plaster | Earthen Plaster | Natural Plaster | Dancing Rabbit Ecovillage

"lime plaster" obviously has lime in it, I get hydrated lime at southern states for 50lb bag at about 8$, mix it with sand, water, and "cat tails" broken up as the fiber, some people use hair or finely shredded hay (don't remember the exact ratio)


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## NW Rancher (Mar 8, 2008)

"Cob" usually describes the material used to build structurally, comprised typically of clay, sand, and straw. "Plaster" is the coating used to cover cob, can be made from lots of stuff, but in cob building it usually is clay and sand, sometimes with small fibers from chopped straw or the like. If you are trying to coat something, you should be able to dig some clay, add some sand, and make a plaster. If you are trying to build something, dig some clay and mix it up with sand and straw. Typically lime isn't used in that type of construction.


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## Seeria (Jul 21, 2006)

Love cob. You can find a lot of info from places like Last Straw and Cob Cottage


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