Is Cob A Composite?

What is a COB?

Cob is a structural composite of earth, clay, straw, sand and water that is hand-sculpted into wall decorations.

What is COB made out of?

Cob, cobb or clom (in Wales) is a natural building material made from subsoil, water, fibrous organic material (typically straw), and sometimes lime. The contents of subsoil naturally vary, and if it does not contain the right mixture it can be modified with sand or clay.

What is the difference between adobe and cob?

The most basic difference is that adobe is formed into rectangular bricks which are dried in the sun before being used, while cob is built wet. Cob therefore lends itself to organic shapes: curved walls, arches and vaults. Building with cob is a sensory and aesthetic experience like sculpting with clay.

How long do cob walls last?

Any type of clay can be used, but be careful not to use silt which can sometimes appear like clay. The oldest cob house still standing is 10,000 years old. Cob is strong, durable and cob houses should stand forever as long as their roof is maintained and the property is looked after properly.

Where is the oldest cob house?

Cob is one of history’s oldest building materials, and has been used all over the world. Many of the oldest standing structures in places like central Asia, the Middle East and sub Saharan Africa are made of cob. Known regionally as “tabya” cob was also used commonly in the Maghreb and al Andalus regions.

Is cob a good insulator?

Cob has great thermal mass but poor insulation value. In very cold weather, especially when the sun doesn’t shine for extended periods, you will lose a lot of heat through those cob walls. A more efficient approach would be to make most of the exterior walls out of a more insulating material such as straw bale.

How do you waterproof a cob?



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WATERPROOFING a COB wall (earthen plaster) with linseed oil


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Does cob wash away?

Why doesn’t it wash away in the rain? Cob is very resistant to weathering. Because of its porous nature, it withstands long periods of rain without weakening.

How long does it take for COB to dry?

Once you make your cob, it will need to dry out full and that can take months to years. The bulk of the moisture will dry out of the walls in the first year, but will not fully cure for 1-2 years past that.

How do you mix cob?

Mix dry sand & sifted clay together first, then add water and start stomping. Use the tarp to roll drier mix on top of the wetter mix, keep stomping, and continue adding water until the cob is sticky but stiff.

How much does a cob house cost?

Cob house cost

A decent cob house can be built for anything ranging around $4,000 – $10,000. However the cost can vary depending on the climatic condition, location and the size of the house. The basic cost, however, may lie somewhere around $2000 – $5000.

Are cob walls waterproof?

I live in Portland, OR, a cool, rainy climate. A: What you’re referring to is an earthen plaster, rather than cob. Cob is a structural mixture of clay, sand, and straw, used to build walls. Lime plasters are waterproof in the sense that they do not get soft when soaked, but they are also very breathable.

Can cob houses be built in cold climates?

A: In places with cold winters, the most efficient homes are well-insulated to keep heat inside. Cob has excellent thermal mass for heat storage, but poor insulation. So an all-cob building will slowly leak heat through the walls in cold weather.

How long will a straw bale house last?

100 years

Are cob houses waterproof?

It’s also water-resistant. The area containing the cob oven and seat isn’t protected from the rain. Yet the cob has stood its ground. How did they do it?

How is a cob house made?

Cob houses are made of clay-like lumps of soil, sand, and straw. Unlike straw bale and adobe construction, cob building does not use dried bricks or blocks. Instead, wall surfaces are built up with lumps of damp cob mixture, compressed, and sculpted into smooth, sinuous forms.