Cob: RE: Workshop photos, more info

[andrea arnold]

hi everyone,

I've received several comments back about the photos,
here's some more info on what we did:

This was to be a small guest room in a woman's back
yard.  It was made small to avoid codes and permits, 
the interior is about 10x12, and yes we are aware that
we have chosen to interpret the "no permit size
guidelines" a little bit.  Legally it's the exterior
that has to measure 10x12 without a permit here.  It
was also made small to make sure that most of the work
could be finished in a five day workshop.  The
building had a post and beam construction, with local
Doug. Fir round posts which we stripped.  The house is
a mix of many many techniques, mainly just for the fun
of it.  It was a great learning experience to get a
little bit of everything first-hand.  The house has a
rubble trench, the drain pipe in the trench was taken
to a dry well instead of out to daylight, because it
was less work and the soil was very well drained.  
      A note on making cob...after a few batches and
working with it building up the wall, it was very easy
to tell whether or not the mix was good.  It was great
to feel like an expert by day 2.  We could all tell
when we needed to add more water, straw, clay, etc and
could easily and quickly tell a good batch from a bad
one.  This pretty much goes for everything we did.  It
was very empowering to learn all these techniques and
confidently feel like you could go away from this and
build your own house.  
      The north wall was straw bale with an earthbag
foundation.  Barbed wire runs between the layers of
bags as an unofficial "mortar".  The bottom two rows
of earthbags are filled with gravel to make sure water
doesn't wick up to the bales.  The top layer of bags
are just filled with dirt.  The bales were dipped in
clay slip before putting them up, so that the clay
plaster would adhere better.  This odes, however, make
them much heavier to work with.  Wooden stakes were
driven through the first layer of bales to secure them
to the top layer of earth bags.  Bales have external
pinning.
     The east and west walls are light straw-clay. 
The north wall is cob and is curved.  We did some
corbelling inside to make a shelf, and there's also
some glass panes that were put directly in and we had
to corbel around those too.  The E, W, and S walls all
have a cinder block foundation.  We did a small panel
of wattle and daub above the entrance, and put a
window through so that you get to see the wattles. 
There is also a wall that is straw wattle... This is
something "new" that Michael stumbled upon.  There are
vertical pieces of wood, but instead of weaving
through sticks as the wattle, we used long handfuls of
straw dipped in thick clay and wove the straw bunches
through, so that the "wattle" and "daub" steps are all
in one.   We all really liked this technique.  It's
much much much faster than light straw-clay or regular
wattle and daub.   We also used this heavy clay straw
mix to cover the earth bags as a prep for plastering. 

     The earthen floor...base was tamped, then 4"
gravel tamped and leveled.  Then a cob like mix that
was high in sand (less shrinkage/cracking) was put
down.  I believe it's called "screeding".  You put
down two 2x4's and level them.  Then you fill in that
section of floor, leveling with another board like a
squeegie down the length of the 2x4's as you go.  Next
you take out the board that's farther away from you
and move it to do another section.  You do the whole
floor by "leap frogging" the same two boards.  This is
MUCH MUCH easier to do than I can explain in words. 
One of the photos I put up shows that a board has been
removed, it is being moved to a new section and
leveled.  Meanwhile, another person has scored the
edges of the empty spot left by the 2x4, and then
started filling it in.   
     We had about 16 adults and several 4 year-olds. 
Aside from the roof and some of the plastering, the
whole thing went up in 7 days.  They are currently
finishing plastering, and the next layers of the
floor.  We also started a cob bench inside, which had
an earthbag foundation.  I'm taking some more
pictures, but it will be awhile before they are
developed.  I'll post the link again when I am able to
add more to it.  
      - Andrea Arnold  

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