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Why earthbag, why not cob?


Joined: Dec 13, 2010
Posts: 1
I've been reading alot about earth bag, and was simply wondering why people even bother useing the earthbag system. It seems like cob or adobe is just as striong, but more ecologicaly healthy? Or is there something I've missed about earthbag that cob doesn't offer. 

Joined: May 26, 2010
Posts: 278
Location: Iowa, border of regions 5 and 6
Cob requires clay.  If you don't live in an area where clay naturally occurs, then you have to pay to bring it in, which pretty much defeats the purpose of building with locally available materials.
Abe Connally

Joined: Feb 20, 2010
Posts: 1492
Location: Chihuahua Desert
earthbags are considerably faster (think days, not months), much more moisture resistant (used for flood control), and don't require a long curing time (cob can literally take years to dry out).

But also, there's the mixing.  Cob and adobe are very labor intensive, and mixing is hard work.  Earthbags are hard work as well, but there is less work with that system.

You can also fill them with anything.

Water usage is a whole lot less with earthbags.

I don't think adobe or cob would be more ecologically healthy, necessarily.  You can find scrap feed bags anywhere, so keeping those out of a landfill is not a bad idea.

There are probably more reasons, but those are the big ones.

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Mori no Niwa

Joined: Aug 10, 2009
Posts: 25
Location: Van Buren Co., MI
I am aesthetically very attracted to cob construction, though my site (and this area in general) are very sandy, so I'd have to have it brought in from some miles away. So recently I've been thinking about earthbag...though neither earthbag OR cob alone would do very well in Michigan's cold winter climate without supplemental insulation. For this reason I'm interested in both strawbale construction and underground/bermed houses with a good passive solar design, in tandem w/ an efficient (masonry?) stove that captures a lot of the heat into some sort of thermal mass and radiates it slowly.

Joined: May 12, 2010
Posts: 52
I love cob.

But you must build a roof on top of the cob building, unless you are in a desert.

The earthbags just continue to spiral up to the point peak and that is the roof.

Ardilla Esch

Joined: Feb 05, 2010
Posts: 183
Location: Northern New Mexico, Zone 5b
It seems like the big difference between cob/earthbag/adobe is what you have available for resources and labor and what sort of design you want.  They are all labor-intensive techniques that you can use various labor saving methods.

For me adobe and CEB blocks are readily available at low cost - so I'm going that route.  Also, I currently live in an oval house and find it somewhat annoying from a space efficiency standpoint.  So the curves that are easy with cob or earthbag are lost on me.  Give me recti-linear construction with rounded edges any day.

Jonathan 'yukkuri' Kame

Joined: May 23, 2010
Posts: 488
Location: Foothills north of L.A., zone 9ish mediterranean
Yes, it is the labor-intensive issue...

Also, in some places (california) cob is not approved for earthquake codes, while earthbag is. 
Len Ovens

Joined: Aug 26, 2010
Posts: 1372
Location: Vancouver Island
jeannacav Cav wrote:I love cob.

But you must build a roof on top of the cob building, unless you are in a desert.

The earthbags just continue to spiral up to the point peak and that is the roof.


I did see rather a lot of dome shaped earthbag buildings on the earthbag site. I also noticed that any of the pictures of the dome shaped earthbag homes were as first built. That is empty without furniture. Except for one which had a failed or at least failing roof. I did find a number of earthbag homes that looked like they had been lived in for some time, but they all had a "real" roof. I also read the FAQs through. They state that the dome roof is not for wet climates... so the earthbag dome is ok for a desert, but not where it rains, same as cob. BTW, the earthbag dome is also not recommended to be buried. It is ok to berm against the walls so long as there is a vapor barrier on the outside of it. (at least all of the plans I found had it) I think sharp gravel in chicken wire might be good for a bermed wall.
I agree. Here's the link:
subject: Why earthbag, why not cob?