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Cob is a mixture of approximately 1 part clay, 4 parts sand and 1 part straw. You can buy bagged clay in powdered form (go to Laguna Clay for local distributors) and masonry sand from your local supply store.
How do you make cob blocks?
Commonly, barley straw is used in Cornwall cob walls.Mixing the Cob: Lay out your tarpaulin. Distribute your clayey subsoil and straw on the tarpaulin. Add some water to your mixture and get your feet dirty by stomping the mixture together. Turn the mixture from time to time to ensure it is mixed well.
Can you make cob with any soil?
The best cob is made by having a range of individual particle sizes, from fist-sized stone to gravel (minus to grit) and sand to fine silts that are found naturally in the clay. Like a good mortar mix, the more sharp and angular the particles are, the better the results will be.
What kind of clay is used for cob?
A: Almost any sort of clay can be used for making cob. Non-expansive clays are best, including those generally sold as “fire clay” and “mortar clay.” Lincoln clays are ideal – very sticky but not highly expansive.
What is COB block?
Heritage Cob Blocks Our cob blocks are traditional structural building blocks made from a mixture of subsoil, aggregates and straw. They are ideal to either restore traditional cob walls in need of repair or to build the perfect eco-building from new. Our cob is available in mass form as well as dried block form.
What is a cob brick?
Cob bricks have a high density that gives them a high thermal mass and sound insulation. They are well suited for modern buildings as well as old. Cob bricks absorb odours and water vapour. Cob bricks can be bedded in a clay or Lime mortar.
How long will a cob house last?
How long does cob last? The oldest cob house currently standing is 10,00 years old. If this doesn’t speak to how strong and durable cob houses are, then nothing will. Cob houses are built to stand forever as long as their roofs are maintained, and they are properly looked after.
What happens to cob when it rains?
Cob is very resistant to weathering. Because of its porous nature, it withstands long periods of rain without weakening. However, too much exposure is best avoided by the “boots and cap” strategy: wide roof eaves to protect the walls and an impervious foundation.
Are cob houses damp?
Cob properties were generally built on a stone plinth, so don’t be dismayed that there is no damp proof course. Cob needs to maintain its own micro climate, so that it’s neither to wet or too dry. Lime mortar has a key role to play here as it allows the cob to breathe and ‘wick’ away any excessive damp.
What is the procedure for mixing cob?
You will need a large tarp and 4 or 5 five gallon buckets. Gather The Materials. Get all of your materials close to your building site. Place The Tarp. Lay out your tarp on a flat space. Measure Materials Onto The Tarp. Dry Mix The Materials. Add Some Water. Mix With Your Feet. Flip And Repeat. Add The Straw, Mix, And Complete.
How long does it take to build cob house?
Cob building lends itself to incorporating salvaged and eclectic building materials. This ìhobbit houseî in Wales was built in four months and cost about $4,600 in building materials.
How much clay Do I need to make a cob oven?
So total clay needed is about 25 gallons for a 22-1/2″ oven, about 35 gallons for a 27″ oven, and about 50 gallons for a 36″ oven. Sand: Sand is your aggregate. It reduces shrinkage of the clay as it dries and it adds total strength to your oven walls.
How thick should a cob wall be?
The walls of a cob house are generally about 24 inches (61 cm) thick, and windows were correspondingly deep-set, giving the homes a characteristic internal appearance. The thick walls provided excellent thermal mass which was easy to keep warm in winter and cool in summer.
Are cob walls waterproof?
It’s also water-resistant. The area containing the cob oven and seat isn’t protected from the rain. Frenk and Nicole made their cob mixture out of clay, straw and sand.
How much does it cost to build a cob house UK?
It will depend on site accessibility and how much adjustment is required to the onsite sub-soil, but usually the cost of the cob itself, including labour and materials, will be no more than £300 per cubic meter. In practice, this means between £25,000 and £40,000 for a typical three bedroomed house.
How strong is a cob house?
Cob house is extremely durable as the base material for its structure is natural re-bar which gives strength to the building. The eco-friendly home is also earthquake resistant as the whole structure acts as one monolithic piece which doesn’t develop cracks when the earth shakes.
What are cob walls made of?
Cob is a mixture of sandy-sub soil, clay and straw. It’s mixed by crushing the particles together by either dancing on it or using the head of a digger. The sandy-sub soil must be sharp and ideally contain angular stones and gravel – this will make it stronger.
What is cob wall construction?
Cob walls are laid in courses, each one being left to completely dry before the next one is laid. In this way, the walls are built up steadily, tapering slightly as they rise. As cob is strong in terms of load-bearing, two-storey buildings are possible.
