“Cob” refers to a mixture of clay soil, sand, water and straw, which is well blended in rather arbitrary proportions (dictated by the clay content of the soil) and used to form a structure. “Cob” means “gob”, more or less. “Monolithic Adobe” describes its rock-like mass. Many mix with bare feet, while others with boots, others with cement mixers, horses and, you get the picture…
“Adobe” is a term with which you may be more familiar. Adobe is made of the same materials but it is pressed wet into forms and allowed to bake into bricks in the sun. The structure is then constructed of the bricks, usually with a coat of plaster applied inside and out to finish it. Brick construction has been shown to be far more likely to fall apart in earth quakes. With cob construction, or “monolithic adobe,” the walls as a singular woven together unit become dried and strong like a giant adobe brick.
It is possible that mud was among the very first “permanent” construction materials. Cob buildings are standing today, still useable, that were built over 1000 years ago. Cob buildings in England have been continuously inhabited for over 500 years. There is a 10-story cob apartment building in Yemen that has been continuously occupied for at least 900 years. (See Hand Sculpted House book for photo)
A cob house is usually built in the following manner:
- A trench, about three feet wide, is dug three or more feet deep (far enough to allow the base of the foundation to sit below the frost line). The trench is filled with rock or “deconstructed” concrete or some similar material. The foundation wall is usually extended at least a foot above the ground level.
- Cob is applied directly to the foundation wall and is built upwards, to whatever level the builder wants to place the roof eave. Anchors for doors and roof can be embedded in the cob walls; openings are left for doors. Windows are usually built into the walls as they go up, with lintels embedded above the windows for load-bearing. If careful planning is applied to the walls mass, large poles bound into massive earth walls can hold a roof in the fiercest of winds, while promoting cool in the warmest times. Any of a variety of roof styles can be utilized.
- The walls are plastered, usually with a straw-less mixture of clay, sand and lime. Often elements such as egg, flour, milk and other natural elements will appear as favorite indoor or outdoor wall protection and coloration recipes.
- Plumbing, heating, electrical lines and appliances can easily be accommodated, either by building them into the plans and construction, or adding them later.
- Checking out other sites such as the Cob Cottage Company or Kleiwerks will help point you in all the right directions.
Advantages of cob construction.
Most earth-based materials can be had free of charge provided the owner or builder is willing and able to scrounge, which requires a truck. Dirt is usually free. It is rare that good cobbing soil can not be found near a building site. Foundation material is readily available– slabs of broken driveways and concrete floors, urbanite or broken cement pieces are ideal and can be found anywhere in a city or town where a building, basement or sidewalk is being razed. Sometimes we can be paid for hauling away these cement pieces. Making piles of collected broken cement chunks can be a huge service to any community seeking to build many of these homes.
Windows from a building in deconstruction are great, as are windows from junk cars. Car and truck wind shields make ideal living room portals, especially when installed length-wise. We can get sheets of aluminum from the sides of old trailers and sometimes sheets of 3/4 inch and other thicknesses of plywood can be pulled up from old trailer floors and used for roof sheeting. Roofing material is anything that will keep out the rain, really. Earth roofs of rubber pond liner, plywood, cardboard, old rugs and soil are more environmentally interconnected and often used to create the garden or earth-roof seen in some of our photos.
Some suggest high tornado winds and big weather flows will respect the house as a hill within the elements and be less likely to explode or blow apart if built in the round, with an earthen or hill-like roof.
A builder, usually the owner, has nearly unlimited creative license in everything from dimension and shape to the tiniest details within and without a cob house.
They are naturally energy-efficient to cool and heat, provided the builder takes care to insulate the ceiling and attend to solar positioning advantages. Straw bales embedded into north walls can render this even more true. Heat tends to pass out through north-facing walls. Straw bales tend to keep this heat in, better than only earth, which is more porous for air passage. A high-quality cob or earthen wall has a very high straw content which can assist in the need for greater insulating capacity.
It is indescribably satisfying to build your own house without using materials that harm you, your neighbors or some people or animals on the other side of the world. Knowing no harm or waste has been caused either from obtaining them or from their effects after manufacture such as the gassing off of rugs, fabrics and paints can put a highly attentive consciousness at a peaceful rest.
1. It is time consuming. It is labor-intensive. 1a. But less than you might think. 2. It makes the need for community obvious, while demonstrating our inherent unified power. A large family group can erect a small family home in a similar amount of time it takes for a modern construction company, only the materials and approach are different. About three months, on average.
This article is good for those not familiar with this building process, and it is good for folks who have land and need basic information about what is involved with building from earth. It is written for folks who live on or near Pine Ridge, reservation.
It also says thanks to those folks last year (2003), and this year for all the help and hard work. The first article described the project and sustainable community development possibilities of earth home building in general. For the most effective green lifestyle planning available, search through this site careful and bookmark any pages that will help you link to labor, land, materials, designs and any other village planning information you may need. Feel free to ask questions or make suggestions.