As more people look to living off the grid as a viable life choice, many age old techniques, practices, and materials are seeing usage once again. One of these materials is cob, cob is an all natural building material usually made from clay and straw sometimes including sand, lime, and other trace ingredients based on local soil conditions.
2-story cob cottage with green roof
Cob has been used as a building material all over the world with examples being found all over the globe from central Asia to the American Southwest to North Europe with some examples of cob construction dating back to the dawn of civilization itself. Most of us are familiar with the use of cob in England dating from the 16th century onward, which is primary composed of clay-based subsoil with sand, straw and water added to it, which was then built layer upon layer to construction a structure.
Diagram showing cross-section of cob wall with stone foundation, cob wall, earthen floor, timber second floor and roof.
Fast forward 500 years to today, where most building are constructed using modern concrete, steel, and processed stick lumber cob is becoming an attractive alternative. So what does cob have to offer over these newer and faster means of construction? First off, cob construction is incredibly simple, it requires no special or heavy equipment (in most cases), is sourced from local materials, and can be made in small batches to allow for any construction schedule. Secondly, as most material can be sourced locally for little or no cost, and construction can be completed without specialized equipment or knowledge, cob allows homesteaders to construct their own cottage, cabin or other structure.
Cob cottage under construction, notice the stone foundation and the window frames being held with temporary supports as the cob is built up around them
Beyond the benefits of its construction and materials, cob has plenty of other positives that will be attractive to many homesteaders and diy'ers. Due to its composition its naturally fireproof, and because of their thickness and density it create excellent thermal mass making heating in the winter and cooling in the summer relatively easy.
Main room of a cob cottage with cob dining nook and a wood-fired mass heater dividing the main space
Also, by its very nature, you can build cob in any fashion you want. Ranging from a simple rectangular cabin to a large free-form structure can be accomplished with cob as its primary material. This same concept applies when creating window and door openings, exterior features, and built-in interior features such as seats, nooks, shelves etc. which can be made exactly to your liking. Perhaps one of the coolest features that can be built into a cob structure is a mass wood-fired heater incorporating either a wood-stove or rocket stove technology.
Heres a built-in cob fireplace and custom bay windows
Living room of a cob cottage with a rocket stove mass heater built as a seat, notice the awesome dragon motif built in as well!
small cob cottage with awesome built-in cob and wood stairway
So hopefully this provides some basic information on what cob is and how you can use it yourself to create something truly unique. Below find some links to useful knowledge sources and books on cob and building with it:
Cob Building Process - Great Summary of what you'll have to do!
Building with Cob: A Step-by-Step Guide
The Cob Builders Handbook: You Can Hand-Sculpt Your Own Home, 3rd Edition