What Is Cob?
Cob is an ancient building material made from a mixture of mud or clay, sand, water and finely chopped straw. It is similar to adobe but does not use any forms, bricks or wooden structure for support. It is used to create structures such as buildings, walls and ovens. The ratio for making cob is three parts sand to one part clay, with the clay making up between 3 and 20 percent of the mixture. Water is added only to moisten the clay. Enough hay is added to hold the mixture firmly together.
History of Cob
The use of cob dates back to prehistoric times. Examples of early cob architecture can be found in a variety of cultures around the world, including Afghanistan, England, Africa and New Zealand. Cob buildings dating back to the 11th century have been found in West Africa. In addition, many cob structures in the United Kingdom are still inhabited today after 500 years of use.
Benefits of Cob
There are many benefits to building with cob. It is inexpensive and environmentally friendly. The building supplies are readily available worldwide. Cob is also fireproof and resistant to seismic activity. The versatility of cob as a building medium allows the builder to create unique, artistic forms.
How to Build a Cob Oven
The first step to building a cob oven is to lay an even layer of brick to serve as the oven floor. A pile of sand is then placed on the brick floor to give the oven shape. The sand pile needs to be slightly taller than the radius of the floor to allow for proper venting. The next step is to begin placing the cob along the base of the sand in a layer 3 to 4 inches thick until the entire form is covered. Once the oven is built, a door needs to be carved out and the sand form scooped away. The oven should be allowed to air-dry for two to three weeks before being used. Cob ovens can be used to make the same food items that a regular oven can.