What is Cob (or Cobb) building? First of all - no corn cobs are involved! I know...it confused me, too!
According to Wikipedia, "Cob is an English term from 1500 for an ancient building marterial that has been used for building since prehistoric times. Cob material is known by many names including adobe, lump clay and clay daubins.
Deborah Maslowski writing on DIY Natural's website, says, "Cob house construction is an ancient building technique using lumps of earth mixed with sand, straw and water. Cob structures can be used as homes, chicken coops, barns, and even smaller ones for ovens. Cob building is easy to learn, requires no special equipment and uses sustainable materials. About a third of the world's population lives in earthen homes and cob is only one type. It has been used for centuries in much of the world, but has just begun to make its way into the US."
The cool thing about cob is, according to Maslowski, that it makes organic shapes easy to create. Most cob buildings are made with curves, bumps, and flowing lines. Roofs are often constructed the same way, and many are made with a flowing room. "Some are built with moss in the roof and some with a tarp -like fabric for more of a teepee effect. Whatever you do, just be sure it's right for your climate," stated DIY Natural.
Once the foundation for a cob building is completed, the fun begins. Using your feet (with or without mud boots), mix clay, sand and water until completely combined and then add long pieces of straw. The finished cob should form a ball and retain shape when put into position. Use the lumps of cob to form the bottom perimeter of the building and any interior walls. Make sure you have planned for any doors(s) and window(s), measuring carefully. Use a ruler to ensure that each layer of cob is the same width.
The roof can be made of any weather-proof material - or you can use the European technique of growing grass or vegetation on top!