What is Cob? It is an old English word for building with earth. It is similar to adobe, but much simpler since no adobe blocks need to be made prior to construction. It is a truly recyclable building material. Cob building is easy to learn and inexpensive to build.
Cob buildings have been built in Britain since before the 1400’s and are found in many other countries around the world including New Zealand and the United States. Earthen buildings are the most commonly built structures in the world. Worldwide, more people live in earthen structures than any other type of building structure.
Hand or shovel formed lumps of earthen materials are used to build Cob structures. A cob mix consists of soil, sand/small stones, straw and water. Soil conditions dictate the exact mix of ingredients. The mix dries to a hardness similar to concrete. Cob walls are so strong that an eight inch or thicker wall, one or more stories high, is fully load bearing.
No forms are needed in the building process due to the stability of the cob mix. This promotes freedom of creativity while building your structure. Curved structures can be easily erected because of the lack of forms. Structures can be sculpted as they are created to form unique monuments. A curved structure is also much stronger and more stable than a straight wall or rectilinear structure.
A cob structure is one unit (monolithic) without mortar joints as are found in adobe buildings. This also adds to the building’s strength and integrity. Cob is also fireproof.
Building with cob is a unique sensory experience. Unlike more traditional forms of building, no power tools are needed. In addition, material size can be tailored to the individual builder’s physical strength. The safety of the building process allows people of all ages, from 3 years old to 100, to participate in the building process.
Cob integrates well with other types of building materials such as straw bale, light clay, timber frame, adobe and even conventional wood framed structures. It is common to use more than one alternative building material when creating a structure. This allows the builder to incorporate each type of building material where it would be most beneficial for structural, energy conservation and/or aesthetic reasons.
Remodeling is simple as cob walls can be added to, cut out to make room for a new window, or reshaped at any time (even after the wall has fully dried). Cob furniture, shelving and wall nooks can be easily built into any structure. Recycled building materials such as windows can be utilized no matter how odd their size.
Cob is very resistant to weathering and can stand long periods of rain without weakening. Roof overhangs and plaster wall finishes can further protect the cob from the elements. In addition, cob walls provide excellent solar mass for passive solar designs.
Cob building is fun and affordable whether you are building a fence, a garden area, a shed or a home. Cob building is an exciting alternative to conventional building.