Cob: cob in forms,monolithic cob vs blocks of adobe and ballistic resistance?

[Shannon C. Dealy]

On Mon, 28 Aug 2000 IBXeri at aol.com wrote:

[snip]
>     I understand that cob should not be built in long straight lines but 
> adobe blocks can be.I would think that the monolithic nature of cob would 
> make it stronger than adobe blocks not weaker.What am I missing?

There is nothing wrong with long straight walls, but to keep them stable
in the event of an earthquake, truck running into the building, etc., you
will either need to make the wall thicker, build in butressing, or tie
another wall into it (such as interior walls) to help keep it more
stable.  In this regard, there is very little difference between cob and
adobe, identical height/thickness unsupported walls should fall over under
roughly the same circumstances, and anything that gets in the way (like a
person) will get crushed.  For marginally supported walls (such as a long
wall with supports only at the ends), cob should do a little better than
adobe because of it's monolithic structure,

>     Is it possible to make a form for a wall and pour/lightly tamp the cob 
> into it and thus build a wall at a faster rate than the 6" to 12" rate.Of 
[snip]

Lots of people talk about this, but I can't recall anyone doing it, and I
wouldn't expect it to gain you anything.  First as you mentioned, you
would have to be able to mix enough cob to build faster, and second, while
you could build a form, by covering the cob with a form you would
significantly slow the drying of the cob (by greatly reducing it's
exposed surface area), with the result being that you would need to leave
the forms on for a long time, since until the cob has dried a fair bit, it
would need the support of the forms to keep the bottom of the wall from
smushing out (I believe that "smush" is the technical term :-)


>     Hate to go here but ..........I live in Oklahoma in tornado alley and 
> would like any info on the ability of cob to stand up to high velocity 
> projectiles.I saw a thread on cob vs bullets but not what I am really looking 
> for.I know there have been tests about 2x4s shot at high velocity at many 
> types of construction I just don't know where to find them.I read somewhere 
[snip]

I doubt that it has been tested for this type of thing, but if you make
your walls thick enough they should be able to withstand just about
anything.  Of course there is still the issue of the roof . . .

Shannon C. Dealy      |               DeaTech Research Inc.
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