Cob: RE: Very succulent free shed

[John Fordice]

Dena & all cobbers,
Louis' experiences seem to relate to building with stone, gravel &
portland cement.

If you are asking this question also relative to building with cob, I
can relate my experiences.

The Northside Garden project was of cob walls built over a period of
about 1 1/2 years on a weekend volunteer basis.  We usually worked 4 to
6 hours one day a week & consequently had to keep the top of the walls
soft enough to accept the new applications of cob the following week. 
This was accomplished by making sure the top of the wall was covered
with LOTS of thumb holes when we finished a days cobbing.  These
indentations, usually about 1" or so deep and very close together, were
filled with water when we finished & then we covered the top of the wall
with saturated burlap.  This was all covered with those inexpensive
woven blue tarps which are readily available.  We made sure to tie or
weight the tarps down to keep them in place.  If there was a break
longer than one week in the cobbing I'd come back to the site & re-wet
the top of the walls in the interim.  Finally, when we started up a new
session. the first thing we did was pull the tarps & re hose down the
burlap making sure to fill all the holes.  This could then soak into the
top of the wall while we were mixing the cob for that day.  This worked
pretty well & we were able to keep a fairly good condition of the
continuous wet into wet process which is so critical to a well cobbed
wall. 
There were a couple of places on the wall where, having worked abound
the building which is a total distance of about 50 feet, our attempts to
keep the long ago sections of unfinished wall tops moist was not
successful.  The result was that we wound up cobbing onto a section of
wall that was really pretty well dried out, and this did not work out
very well.  This point in the wall also happened to be at one end of a
major lintel over an opening in the wall.  The combination or the
cobbing onto a dry wall plus the natural shrinkage that occurs at the
ends of lintels causes a fairly major crack in the wall at this point.

To avoid this, in the future, I think I'll do two things:

1. place crushed bamboo in the cob about 6" above the lintel & extending
at east 2 of 3 feet past the ends of the opening - this is to compensate
for the natural cracking that sees to occur at the ends of the lintels anyway.

2.  I'm considering on my next building trying a technique of working a
running cobbing AROUND the building instead of cobbing all around the
building & working up in horizontal layers.  The process of long
horizontal layers works well when you have lots of workers on a
continuous basis as in a workshop situation, but this technique has the
built in problem of keeping allot of wall moist on top if the work is
not continuous.  The process I'm considering is to start at one side of
a major opening & build the wall up so that the end is at a more or less
45 degree angle at the unfinished end.  This will limit the area to be
kept moist to just the end of the wall.  A 6' high wall wall on top of
an impervious stem wall would mean that you would be cobbing on a sloped
45 degree surface of around  8 1/2 feet & this should be pretty easy to
do as 6" to 8" high lifts with a small crew on an intermittent or
continuous basis and still keep the working part of the wall moist.

Hope this helps

john fordice
maker of cobbers thumbs
the cob code project   

Dena Marchant wrote:
> 
> Hi Lois,
> 
> Do you have any words of wisdom about building over
> a period of years?  How do you protect partially finished
> walls, etc.
> 
> Dena
> 
> > > >-----Original Message-----
> > > >From: owner-coblist at deatech.com [mailto:owner-coblist at deatech.com]On
> > > >Behalf Of TICKLETOWN at aol.com
> > > >Sent: Friday, March 16, 2001 8:29 AM
> > > >To: coblist at deatech.com
> > > >Subject: Cob: Very succulent free shed
> > > >
> > > >
> > > > I've been reading this list for a while now - I asked my
> > > >daughter whose
> > > >computer I use to switch here from the strawbale list, which I
> > > >enjoyed but
> > > >wasn't into as much as cob. I'm trying to learn as much as I can about
> > > >building sustainably using onsite materials. I've read a few
> > > >books (thank
> > > >goddess for inter-library loans) and tried a little tiny cobbing.
> > > > After three years of tenting on site in the summer while we worked, I
> > > >finally moved into my cosy little half-underground home this
> > > >fall. When I
> > > >planned my home I knew nothing about cob or I definately would
> > > >have gone in
> > > >that direction. I opted for a very small, dug out of a southern slope
> > > >u-shaped room with glass on the south and west. We had a
> > > >horrible time with
> > > >the roof since I had insisted on free form curved walls made
> > > >using Scott &
> > > >Helen Nearings' stone building techniques. I finally had to
> > > >give in and go
> > > >with a (somewhat) conventional timber framed living roof. My
> > > >home is very
> > > >lovely but I feel bad about the portland I used in the walls
> > > >and some of the
> > > >other non-sustainable downright nasty materials (waterproof
> > > >roofing material,
> > > >nails, even the small bulldozer and back-hoe). Seems that as I started
> > > >building I started learning and the more I read about natural building
> > > >methods the more radical I became. I've been fantasizing about
> > > >an all natural
> > > >little cob house for quite a while and imagine my surprise
> > > >when I actually
> > > >SAW it. Thanks Shannon. I'm totally empowered and motivated to
> > > >finish my own
> > > >little burrow now and REALLY get into some dirt! And sticks
> > > >and stones and
> > > >grasses. I'm eager to see how your roof turns out - I didn't
> > > >feel able to do
> > > >thatch (thought you had to have the right grasses and tons of
> > > >know-how)  but
> > > >now I'm wondering. What about cattails? Also your jar windows
> > > >were neat. In
> > > >fact the whole little shed looks downright SUCCULENT. Keep us posted,
> > > >
> > > >
> > > >                      Lois
> > > >
> > > >