[Cob] cob vs adobe

[Leslie Moyer]

Part of what gives cob its strength is it's monolithic form, with straw 
from one cob "knitting" into the straw from another cob...as well as the 
clay platelets aligning with one another and becoming monolithic.  When 
you use adobe bricks, you lose both of these benefits.  Adobe has 
compressive strength, but very little tensile strength bridging from one 
adobe to another.  Basically, I think you would be losing one 
dis-advantage (cracking) but gaining a couple others.  Besides, with 
cob, the inside of your oven will be round-ish--domed on the inside.  
This, too, gives it strength.  Once you put rectangular adobe blocks in 
there, you lose not only some oven efficiency, but also some of the  
integrity of your structure. 

Cracking just isn't that big a deal.  If you build it properly 
(especially using appropriate amounts of clay & sand & straw), a crack 
will rarely affect the function or integrity of the oven.  And if it 
does, you just slap some more mud onto it.

Someone asked about buying pre-made adobe bricks. I don't know for sure 
where you can buy them except that they're more readily available in New 
Mexico, U.S. and Mexico, where adobe is a traditional building material. 
Other than that, I don't imagine they're readily obtainable. 

--Leslie

Mary Lou McFarland wrote:
> I was wondering..... I haven't built my oven yet but I had a thought.  I've heard a number of people complain about cracking and crumbling on the inside of their cob ovens.  It occurred to me that if the first layer over the sand form were of adobe brick that with it being predried, it might help to eliminate part of that problem.  Once the interior was built of the bricks then the other layers could continue as usual.  Just a thought.
>
> Mary Lou
> _________________________________________________________________
> Do more with your photos with Windows Live Photo Gallery.
> http://www.windowslive.com/share.html?ocid=TXT_TAGLM_Wave2_photos_022008
> _______________________________________________
> Coblist mailing list
> Coblist at deatech.com
> http://www.deatech.com/mailman/listinfo/coblist
>
>