Cob Yoda's cob house

[Shannon C. Dealy]

On Wed, 3 Dec 1997, Will Firstbrook  WCB of BC wrote:

[SNIP]
> One of the area's that seems tricky is my eldest son's room. He wants it
> to look like Yoda's house in "Star Wars" movies. Everything in the room
> will be curved (uneven yet smooth) cob seems to be the perfect medium.
> The whole ceiling will be curved arches. The walls will have rounded
> nooks and rounded windows.  A rounded (top) hallway will connect this
> room to the main part of the house. This room would be a separate pod on
> the East side just behind the East Tudor entrance. Any Ideas on how this
> could be done?
[SNIP]

I have no doubt that a cob dome roof can be safely constructed using
corbelling, as long there is sufficient arch to the dome.  It is
important to remember that when you build an arch or dome, much of the
force acting on the materials are compressive rather than tensile or
shear forces, and compressive strength is where cob excells.  My concern
with using cob for any kind of roof is that should there be any failure of
the roof's protection from the weather, it might kill somebody before you
are aware of the problem.  Personally I would consider this to be to much
of a risk to take, though it might be reasonable to try cob arches as your
roof support.  If you want to achieve the yoda effect, I would go ahead
with the cob walls and sculpture work, but then put a small geodesic dome
on the top to give the rounded roof structure and plaster the interior of
the dome with cob to keep the interior effect.  You would still need to
have wide eaves around the outside to protect the cob walls however.  If
you really want the dome effect inside and out, you might be better off
just building an inexpensive geodesic shell as your entire exterior and
use cob for the interior.

Shannon Dealy
dealy at deatech.com