If you’ve delved into alternative and off-grid housing options, you’ve probably encountered cob homes. These charming, fairy-tale-like structures are more than just a fantasy—they’re quite practical in reality.
Despite being an ancient construction method, cob building offers remarkable potential for creating sustainable and cost-effective housing. Modern cob homes are not only durable and energy-efficient but also visually striking. However, this approach might not be the perfect fit for everyone.
In this overview, we’ll examine the advantages and disadvantages of building with cob to help you determine if this unique construction method aligns with your needs.
WHAT ARE COB HOMES?
A cob house is constructed from a blend of clay, sand, and straw. When these materials are mixed in the correct proportions, they form a highly durable and versatile building substance.
Often referred to as earthen or mud houses, cob cottages have a rich history, having been commonly built in Europe and Africa for centuries. Although their popularity waned with the advent of modern construction materials, cob homes are experiencing a revival as a sustainable and appealing alternative to conventional building methods. In North America, they are becoming increasingly popular as interest in natural building techniques grows.
Cob houses are typically constructed by hand, without the aid of power tools or machinery. The main material used is the cob mixture itself, which, when sufficiently mixed, is workable and can be shaped. Builders create thick walls by molding the cob by hand, starting from the foundation and progressing up to the roof. Once the walls are dry, they are often coated with clay or lime plaster to enhance their durability.
Cob homes differ from other natural building techniques like straw bale or earthbag construction. Straw bale homes use bales of straw as infill between wooden frames, which are then covered with plaster. Earthbag construction involves stacking bags or tubes filled with soil, secured with barbed wire, to create the structure, and like cob and straw bale homes, these are also finished with plaster. While all three methods can offer similar exterior appearances, they each use distinct techniques and materials in their construction.
COB HOUSE PROS AND CONS
COB HOUSE PROS
ENERGY EFFICIENCY
Cob walls have high thermal mass, meaning they absorb and store heat during the day and release it slowly at night. This helps maintain more stable indoor temperatures compared to homes built with modern materials. In summer, cob walls also help keep the interior cooler. Because cob homes require less energy for heating and cooling, they are more eco-friendly, especially in warm, dry climates.
SUSTAINABILITY
Cob houses are built using materials that are often found on-site, especially clay or mud. Sand and straw can usually be sourced locally if not available at the building site. This reduces the need for conventional building materials and lowers transportation emissions, leading to a significant decrease in the embodied energy of construction.
AFFORDABILITY
Cob houses are among the most affordable to build. The materials are typically inexpensive and readily available. Since many components can be sourced for free on-site or nearby, and homeowners often do the work themselves, the overall construction costs are reduced.
DURABILITY
Cob homes are extremely durable and can last for hundreds of years if properly maintained. Many old cob structures still stand strong around the world, from England to Africa. Cob is known for its resilience against earthquakes, pests, rot, and mold.
INDIVIDUALITY AND ARTISTIC EXPRESSION
Cob homes can be shaped into almost any design because they don’t use traditional framing. This flexibility allows for creative designs, including circular or curved walls and unique features. Cob also lets builders add artistic touches like carvings and custom-built furniture, fireplaces, and shelves, both inside and out.
FIRE RESISTANCE
The main ingredients in cob—clay and sand—are naturally fire-resistant. This makes cob homes more fire-resistant than many other types of buildings.
DURABILITY
Cob homes are incredibly durable and can last for hundreds of years if maintained properly. Many old cob structures are still standing around the world, from England to Africa, showcasing their long-lasting stability. Cob is a strong material that can withstand earthquakes and other natural disasters, and it is highly resistant to pests, rot, and mold.
INDIVIDUALITY AND ARTISTIC EXPRESSION
Unlike conventional houses built with frames, cob homes can be shaped into almost any design you can imagine. This flexibility allows for unique features like circular or curved walls, window frames, and roofs.
Building with cob is similar to sculpting with clay, giving you the freedom to create distinctive designs with curves, patterns, and carvings. This creative freedom extends to both the interior and exterior of the home, where cob can be used to build stunning walls, as well as custom features like built-in furniture, fireplaces, ovens, and shelves.
COB HOUSE CONS
LABOR AND TIME
Building with cob involves a lot of labor and time. Each layer of cob needs to dry before the next one can be added, so completing a cob house can take months or even years, especially if you’re doing most of the work yourself. If you need a quick construction process, cob might not be the best choice.
Cob construction also requires skills that many people don’t have. If you’re determined to build with cob, you might need to hire a professional or take a course to learn the techniques. If you hire someone, the labor costs might be higher than for traditional building because of the extra time and skill involved. However, many cob builders offer workshops or share their knowledge for free, and you can speed up the process by working with friends or family.
NOT IDEAL FOR COLD AND WET CONDITIONS
Cob isn’t the best material for areas with long periods of wet or cold weather. Cob can break down if it’s constantly exposed to moisture, although a good roof can help protect it. Many cob homes do survive in regions with consistent moisture.
While cob’s thermal mass is great for warm and moderate climates, it doesn’t help much in very cold conditions. Heating will still be needed regardless of the building material. To reduce heating costs, you can use passive heating methods, large windows, solar energy, or even build your cob home inside a greenhouse, as some people have done in Norway.
DIFFICULTY WITH PERMITS AND INSURANCE
Getting permits for a cob home can be challenging because traditional building codes often don’t cover cob construction. Some areas only allow conventional building methods, so you might not be able to get approval for a cob house.
Before starting your project, check with your local planning office to see if there are any restrictions on alternative building methods and what codes you need to follow. You might need to hire a structural engineer or other professionals to get your plans approved.
Insurance can also be tricky since cob homes don’t fit neatly into standard categories like stick-built or mobile homes. Finding insurance might be difficult, so you’ll need to explore your options carefully.
FINANCING PROBLEMS
Getting a mortgage for a cob home can be difficult because many lenders are unfamiliar with this building style and may be hesitant to finance it. You might find a lender willing to work with you, but it could be a long and challenging process.
Consider alternative financing options such as owner financing (if buying an existing cob home), bartering, or lease-to-own arrangements to get the funds you need.
SO, WHAT’S OUR TAKE ON COB HOMES?
If you’re thinking about building or buying a cob house, keep in mind that it involves a lot of work and you’ll need to get the right permits.
However, if you’re after a sustainable, affordable, and unique home made from natural materials that can last for centuries, a cob house could be a great choice! Just make sure to do your research so you know what to expect.
You can start small by trying out cob construction with simpler projects like cob ovens or playhouses. This can be a good way to learn about how cob works in your area. If you decide that a cob house is right for you, you’ll have a unique, hand-built home to enjoy for many years!
CONCLUSION
Cob houses, with their unique blend of natural materials and ancient construction techniques, offer a promising path towards sustainable and comfortable living. Their advantages, such as excellent insulation, durability, and low environmental impact, make them a compelling option for those seeking eco-friendly housing solutions.
While cob construction may present challenges in terms of labor intensity and potential moisture issues, the benefits often outweigh the drawbacks. As technology advances and construction practices evolve, it’s likely that cob houses will become even more accessible and practical. Ultimately, the decision to build a cob house is a personal one, influenced by individual preferences, lifestyle, and environmental values.
