[Cob] RE: Susan's foundation

[Mary Lou McFarland]

My experience with re-bar is with roads, not building, so here goes.  All 
re-bar is rusty,  but it doesn't matter.  In order to create rust you need 
air, moisture and of course, the metal.  The rebar should be elevated within 
the concrete so it isn't sitting on the gravel.  Ideally it will be smack 
dab in the middle of the thickness of the concrete.  If your location is 
properly drained then the concrete shouldn't wick excessive moisture so 
you've taken care of that ingredient of the equation.  As long as the 
concrete doesn't crack then there will be no air reaching the re-bar.  If 
your concrete should crack then fix the crack promptly.  If properly done 
then the surface rust already on the re-bar is inhibited.  I wouldn't use 
any kind of wire because it just isn't strong enough to hold.  When wire is 
used then it 's like a woven wire fencing stuff that is for flat expanses, 
not for a footing, bond beam, stem wall, etc.  Let's say you do have a 
tremor and your continuous footing that your cob wall is built on has been 
re-enforced with wire.  The earth will move the concrete will snap and 
crack.  The wire will break like a string and the broken concrete will roll 
off with the displaced earth.  If it is re-enforced with re-bar the earth 
will still move and the concrete will still crack but the re-bar will hold 
that chunk in place so it doesnt go rolling off and hopefully you still have 
a wall and you still have roof.  You might still have to replace everything 
to make it safe but you will still be around to tell the tale.  Personally, 
I would use re-bar in concrete but I wouldn't use it in cob.  Cob, by 
definition, is a material that breathes and can take in and release moisture 
from the air so you have all the parts to that rusty recipe of air, moisture 
and metal.  There you go, probably more than my two cents worth ,but I hope 
it helps you out.