[Cob] compare stonemasonry

[Amanda Peck]

It kind of sounds to me like you need to talk to a structural engineer.

Width and weight of the wall and placement of the foundation would concern 
me.  Stone walls can be around a foot wide, cob, often half again as wide, 
much wider than nearly all stick-framed walls.  How are you planning to 
widen the foundation  to support this?  In any case you'd probably want 
stone up a foot or so to prevent a recurrence of the flood ("all-natural" or 
man-made--inside or out) from doing awful things to your cob.

If the flood was the river, not the washing machine, that could happen 
again. Stone put up with regular mortar with might be a little more 
damage-proof.

South facing?  the outside stone/cob/whatever will radiate more heat to the 
outside.  Are you planning lots of windows? Do you have a 
stone/concrete/earthen/tile floor to soak up the heat on the inside?

Your standard subdivision "brick" house has a brick facing then a small 
cavity, then the stick wall. The brick does nothing for the house structure, 
you can retrofit a frame house with brick, change your mind and use siding 
instead of brick with not too much trouble.  The two layers, brick--or 
stone--veneer and the standard wood framing get tied together with strips of 
metal nailed to the studs--sticks and buried in the mortar as the outside 
wall goes up.  It would be no particular problem to do something like that.  
It's NOT what you're talking about, though.

Every thing I've seen about cob seems to indicate that piling wide layers on 
top of each other--horizontally--is what gives the wall its strength.  
Putting two vertical layers together--anybody really know if or how that 
would work?  I sure don't.

What really MIGHT work would be a timber frame with infill with one of the 
"light clay" type composites--clay/straw clay/sawdust or woodchip.  You 
might even be able to work around the problems of foundation width that way. 
  Still need to be water-resistant up a ways.  But if you used forms for the 
light clay, you would have less trouble securing the building because it had 
plywood or OSB or salvaged planks temporarily nailed to the framing timbers 
anyway.  A wattle--woven sticks--and daub--earthen plaster of one recipe or 
another, might work the same way.

...............
Donna Strow asks about replacing a (south-facing) stick-built wall with a 
cob or stone wall, leaving the damaged wall in place until a vertical half 
went up inside of the damaged one, then completing the outside half of the 
wall.

................
Here's her complete post:
Um, hi.  Comming briefly out of lurk mode here...  I've found that I end up
storing list letters instead of reading them lately, so please forgive if
this material has been covered before.

What's to love about cob is also to love about stone -- heat capacity.
Could you help me to compare these materials in the context of a project?
(Or even in the context of heat capacity -- which has more, anyway?)

For the project, a flood-damaged stick wall is to be replaced -- actually
two walls that meet at the usual angle are to be replaced.  The plan is to
build the new wall along the inside of the stick wall, then remove the stick
wall from the outside and continue to build the new wall out.  (Is this a
good plan, anyway?  I figure that way I won't have to worry too much about
re-securing the roof, or vacating the property during construction.)

The larger wall is a south wall, by the way.  Hmmm... where do I go from
here?  The stone plan is a little more evolved than the cob plan.  With
stone I would create a beautiful south face for the house and then worry
about the outer layer of stone (that added after stick removed) will shear
away from the inner one.  But with cob I could just leave a rough surface so
the outer layer could cleave.  It might even be warmer than the stone, but
alas not quite as beautiful.  You know, I'm leaning heavily toward stone,
atleast for the outer face (Would stone facia cleave to an inner surface of
cob?  I remember that cement definately did *not* stick to cob)

Any ideas/ solutions/ advice?


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