Cob: cob over traditional house?

[John Fordice]

Melanie,
I don't see why you could not encase your old farmhouse with cob so long
as you studded the building with nails to create a mechanical bond
between the house and the cob.

I do see some potential problems though:

Any cracks that might occur due to the shrinking of the cob over an
object ( the house ) that is not going to shrink along with the cob as
it dries will leave a pathway for rain to enter & it might create dry
rot potential.  A very high sand component will help reduce shrinkage &
might limit this potential.

The eave width of your existing roof might need to be made wider to
protect the cob from falling rain & roof edge run-off.

The biggest concern I'd have is the added load and it's possible seismic
implications.  Wood construction ( I assume the house is wood framed )
has developed to resist the loads of a wood building.  Cob is much
heavier & unless a cob building is properly designed and built as very
thick walls,  it does not have much seismic strength.  Placing a layer
of cob on your building that is not thick enough to support itself in an
earthquake could overload the bracing of a wood framed building & cause
a dangerous situation with the possibility of failure of the building in
an earthquake.  Don't be lulled into thinking this is not a problem if
you are not in earthquake country.  Earthquakes can potentially happen
anywhere on the planet.

john fordice

Melanie Kleiner wrote:
> 
> I was wondering if it is possible to apply cob over an existing old farmhouse (it has that nasty asbestos slate siding now).  There are many cracks and drafts and I thought it might be a less expensive way to reside the house.  Plus I love the look of cob and we could add on to the house with cob.  Any thoughts are welcome!