Cob vs. CEB

Hello all,

First post. This is a cool community and I hope I can contribute much. Unfortunately, I'm gonna have to take out some credit from the knowledge bank tonight. I hope y'all will bear with me

I've been searching for this comparison on the net and have come up fruitless. Does anyone know what the pros and cons are when comparing cob building with compressed earth blocks (CEB)? They both have thermal mass, are resistant to fire. The things I imagine, though, are that CEB isn't as flexible in design (no cool artsy stuff on the walls), but cob seems to be more vulnerable to water? Or do I have that wrong?

Any help is appreciated! Thanks.

Cob needs a lot more water than you may want to use in a desert climate. CEB needs dryer clay than some people ever have in wetter climates.

CEB needs a machine, and even CINVA rams are expensive. Cob needs a couple tarps (for small scale) but you really need a big mixer (or slave labor) for large scale.

CEB can be easier to install in zoned areas because they look like regular brick.

Both are moving and mixing tons of dirt. Do you prefer moving it in buckets or blocks?

The research I've done indicates that cob for walls requires more thickness as you go higher. Some Welsh cob homes has walls 2 feet thick in the second and third stories. CEBs can be dry stacked and depending on their aspect ratio may not need much thickness for stability.
CEBs tend to have good tensile strength and of course have great compressive strength. CEB mixtures range from simply laterite clay to laterite ad portland. Rich clay like that used for pottery may need to have sand mixed in. Cob, as I understand it should be a decent clay, perhaps not potters grade but at least free from large particulates like stones. Similar to monlolithicly poured concrete, cob forms a homogenous structure.

John Zeron wrote:The research I've done indicates that cob for walls requires more thickness as you go higher. Some Welsh cob homes has walls 2 feet thick in the second and third stories. CEBs can be dry stacked and depending on their aspect ratio may not need much thickness for stability.

Interesting. I would assume that as height went up that thickness would need to increase, but I would figure that you'd need more thickness at the base and go thinner as you go up, to reduce the load, and the thicker base would be there to carry the load. It would surely be a strange sight to see an 18" base wall and a 36" second story wall. Seems counter-intuitive to the concepts of structural engineering.