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COB is a mixture of straw, sand, clay and water used as a building material. While wet, it is hand-shaped into walls one or two feet thick which dry into load-bearing structures with the hardness of lean concrete. Yes, cob is just mud and straw; it seems an unlikely material to get excited about. And yet a growing number of people are building with cob and waxing poetical about its many virtues.  

 

Strong

As cob dries, clay particles bond to straw fibers creating a reinforced network akin to concrete poured around steel rebar. Since walls are shaped into continuous curves and not laid as bricks, there are no weak shear joints.

Weather-resistant

Cob very porous, so it doesn't just wash away in the rain. However, excessive exposure is usually avoided by roof eaves and gutters to protect the walls, and a high foundation.

Climate-controlled

Cob has a high thermal mass. In winter the walls absorb sunlight by day and radiate the heat by night, keeping the structure warm. In summer cob homes retain the cool of night so the spike of afternoon heat is not felt inside.

Cheap

Mud and straw are not expensive. (This understatement shows that Quakers do, in fact, have a glimmer of a sense of humor).

Environmentally friendly

The ingredients for a cob structure can be found locally, anywhere. There is not need to chop down and transport trees, line walls with plastic and mesh, spray for bugs, and so on. Cob homes take little energy to heat. And -- let me stress again -- cob is just mud and straw, so it's non toxic.

Fun

Building with cob is an easy, organic, sculptural process. It's hard to capture the silly joy of mixing together a batch of cob and molding it into a wall by hand. Many builders emulate Tom Sawyer and actually manage to charge cob enthusiasts for the pleasure of building their home.

Why did Pendle Hill Choose Cob?

Pendle Hill is committed to simple, healthful, and mindful living. When the time came to build a permanent greenhouse in the garden, cob was the ideal structural choice to uphold these ideals. Cob walls look pretty, cob is cheap, simple, and fun to build with, and the entire community can share in this fun project.

   The east and west walls will be formed from cob, and cob will be used to plaster the north wall and fill gaps between the roof and walls. We will shape cob around the windows in the walls and leave indentations to store equipment. There will be little nooks for candles, and there will be a cob bench in the meditation section of the greenhouse.