Building A Small Cob Wall

While we have used the basic mixture for cob in many places of the house- in the floor, as rough plaster coats, and for sculpting – we have only one small wall that pays tribute to the building techniques of cob.  It is a short barrier that separates the back of the wood stove from an area that will one day be a staircase leading down to the rest of the house.  Only 8 inches wide, it does not have the usual girth of a supportive wall, and rests on a ledge of concrete that was poured with the rest of the foundation and connects to the back of the two foot tall stone hearth.  We embedded an air vent pipe that opens from the outside wall to behind the stove, allowing the stove to draw in fresh air as it burns.

We started the wall with a work party, inviting families, neighbors, and interested friends to lend a hand or foot in stomping, wheel barrowing, and shaping.  Children and cob are a perfect mix and add such a joyful presence to the job!  We used clay from our huge pile gathered for the previous plastering and floor sections, clay that originally came from a farm down the road that dug themselves a huge pond and discovered clear blue clay.  The sand is pit run sand from the island, (a silty and rough sand with lots of rocks – just fine for cobbing with) and straw leftover from the bales we got for the house.  Stomping includes mushing the mix together with your feet on a tarp, adding water as needed and rolling the mix in the tarp once in awhile to help move the bottom stuff to the top.  Inside the house, we took handfuls and pushed it into the growing ledge of the wall, using thumbs and sticks to really integrate each handful.  The work party got us up about 2 feet, at which point the weight of the cob began to cause the wall to slump out the bottom.  We let this part of the progress dry out for a day, then used a saw with large teeth cut into it to trim off the excess cob from the bottom until it measured the right width again.  We could then continue to add on to it until it began slumping again.  The lowest part of this wall reaches just over three feet, and then arches gracefully up another foot behind the hearth and the wood stove.  Then my mom got her hands in there to sculpt a draping vine along the top and dangling down the sides, smoothing out the top of the wall in a rounded curve.  After letting the wall completely dry out (about a month!)  I could finally mix up some green colour samples for the final plastering.  (See my previous post, Final Plastering, for details on mixing and applying natural clay plaster).  Working around the sculptured vine took lots of patience and forgiveness, but in the end the natural quality of the plaster reflects and brings out a beautiful ease and grace framing the hearth.

vine detail before being plastered

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