When thinking of a cob house, images of small, smooth-walled, round cottages set back in the countryside may come to mind. But what exactly is a cob house? What is it made from, and why are they so special? Here we will take a closer look at these quaint and charming English cottages, known for their durability.
At its core, a cob house is a structure made from cob: a mixture of sand, clay, and straw. By mixing these components in the correct ratio, along with some water, a durable building material is made. This material is then built into a structure by layering it on top of a stone foundation. Instead of creating bricks, cob houses are constructed layer-by-layer. The builder applies the cob material a few feet high all the way around the house, then allows that layer to dry before adding the next layer until the structure is complete.
This process creates a cob house’s unique look and explains where it got its name. In Old English, the word ‘cob’ means lump. Since these houses are basically created by lumping the cob material together into your desired shape, the name fits.
By creating thick walls of cob, the resulting structure is somewhat self-regulating in temperature. During the day, the thick earthen walls absorb the sunlight, keeping the interior cool. These walls hold onto the absorbed heat and release it at night as the temperatures drop, keeping the inside warm.
Cob houses are famous for their uniquely curved, rounded, and artistically shaped structures. Since the building process creates smooth, connected surfaces, cob houses naturally take the fall into rounded, organic shapes. Curved walls, rounded archways, built-in bookshelves, and even fireplaces are extremely common. However, the look and structure of the house are far from basic or utilitarian. Beautiful designs and hand-molded artwork are often incorporated into the walls or exteriors.
Because cob houses use natural, local materials for their construction, the interiors and decorations are often also chosen with sustainability and earth-friendliness in mind. Natural woods, stone, cotton, linen, and other organic materials are frequently seen inside cob houses. Earthy colors are often chosen and the outside is invited in with the use of houseplants and gardens.
Cob houses are generally small. Single-story cob houses can be made without the use of wood framing. However, this doesn’t mean that cob houses can only be built as single-story structures. With the use of a wood frame to offer support, two-story cob houses are quite popular.
As for individual variations, the options are limitless. No two cob houses look exactly the same, as endless organic shapes can be created. Popular variations include the incorporation of built-in shelving or countertops. Desk areas, benches, and nooks can easily be shaped into the walls. Fireplaces are molded right into the home and are often connected to large slabs of cob, such as a bench, to increase the amount of heat the stove puts off. This type of stove is called a rocket mass heater.
How long will a cob house last?
Cob houses are extremely durable and long-lasting. With proper maintenance, cob houses have been known to last thousands of years. By keeping the roof in good condition and repairing any worn-down cob, a cob house can easily last for generations.
What are the disadvantages of a cob house?
Cob houses are very time-consuming to make, as each layer of cob must dry before the next is layered on. Therefore, building a cob house can take many months. When completed, the cob house will need to air out for a few months before you can seal the floor and walls and move in. The cob itself will not completely cure for another one to three years, making it very important to air out the house and use dehumidifiers for at least the first couple of years.
Are cob houses legal in the US?
Yes, cob houses are legal in the US. However, exactly where and how you build a cob house will differ depending on your location. Always check your local building requirements and obtain the necessary permits before building.
Are cob houses waterproof?
Cob houses are not waterproof, however, they are very resistant to rain and weather. The cob material itself is best protected from long exposure to rain and water by creating a roof with wide eaves and building on a waterproof foundation.
Cob Research Institute's Cob Code Approved for the 2021 IRC. Cob Research Institute.