The Beauty Of Cob
Earth has been used by humans to build dwellings and structures for over 10,000 years in almost every continent in the world. A technique that has been learned from humans watching how animals utilise their environment. From a swallow crafting a nest using earth and twigs, to termites carving through mud and wood to create miniature palaces. A material created by people made out of a particular mix of natural resources from the ground has been named 'Cob'.
Cob is a blend of clay, sand, straw and water which is soft and supple enough that it can be shaped and sculpted to produce intrinsic and beautiful structures. After drying cob is as strong as concrete. Cob can store and transfer heat. Cob is completely natural, locally sourced, renewable and non toxic. Cob is also a breathable material which has many health benefits to people and animals, it requires very little energy to heat and cool. Using straw bale alongside cob is our preferred building technique. This gives the house extra insulation properties, therefore a better U-value (efficiency of an insulator) than modern building materials. Not only is Cob a brilliant house building material, it is also ideal for making traditional Pizza Ovens due to its superb thermal mass properties.
What are the benefits of Cob?
Cob is a sustainable material that has an extremely low carbon and ecological footprint. All materials use to make Cob are taken from the ground and are locally sourced. Building with cob is the most sustainable building technique available. As well as using green materials the building of a house has little or no ecological footprint and involves no factory processes. Brilliant for our environment compared with modern techniques associated with the industrial revolution.
Modern buildings are full of indoor air pollutants due to inpearmeable walls and gases that are continuously released by unnatural paints. plasters, rendering etc. Cob homes do not have this problem. In fact, cob actually 'breathes' through its tiny pores and keeps air fresh and clear, there is no damp in a Cob house. If you suffer from indoor allergies then living in a cob house could significantly improve your quality of life by eliminating the toxins that may cause them.
Cob can be shaped and moulded in any form for before it dries. This enables the builder and customer to create any design or pattern they wish. Cob has a distinctive marbled pattern and unique colour associated with the clay in your local area.
Safe and Strong
Cob has unique properties which make it as strong and more durable than concrete (see 'How is Cob so strong') the oldest Cob building is over 10,000 years old. Cob is resistant to fire, termites and mould.
Cob is a thermal mass that absorbs sunlight and warms the building over the course of the day, essentially acting like a battery storing and releasing energy. Similarly Cob wall can cool and radiate this into a hot humid building during the summer months. Cob buildings can be designed in order to maximise these properties so no additional heating or air conditioning is needed. This is done through passive solar design.
How is Cob protected from wind and rain?
Cob is a remarkably durable material provided it is treated correctly. In practice this means keeping it dry. Cob walls are finished with a protective lime wash or putty or an earthen plaster. The roof of a Cob building is designed with a large overhang to protect from heavy rain falls.
How is Cob so strong?
Each raw material in a Cob mix has an important part to play in providing a very strong and stable microscopic structure.
Clay particles are microscopic and form tiny platelets, when water is added to the clay it gets between these platelets and pushes them apart. Eventually the water evaporates from between these platelets and they shrink and bind closer together forming a hard mass.
Sand and aggregates are added to the clay when it is wet. These are much larger particles of various sizes giving the mixture more mass and limiting shrinkage. These particles fit together like a jigsaw puzzle with the clay providing a cohesive bond between these particles. The addition of sand and aggregates also helps prevent water from eroding or damaging the material, thereby vastly improving durability.
We also add fibres, typically strong stable cereal crop stems e.g straw. Fibres interrupt tiny cracks if they should develop and prevent them from growing larger and cracking the material. The fibres also act as reinforcement giving tensile strength to the material.
Are modern conveniences possible in Cob buildings?
Cob buildings are fitting with the same plumbing and electrical wiring as a conventional home. They can be fitted with central heating and air conditioning, similarly to a conventional building, in a cob house this is not a necessity. Cob houses are planned using passive solar design which can adequately heat and cool your home all year round. We also offer a range of other ecological solutions to modern conveniences, such as reed bed filtration systems and eco-loos. Effectively living off-grid!
Can I paint Cob walls?
You can paint an earthen wall with clay or mineral pigments, choosing from a vast array of colours and textures. There are many excellent formulas for beautiful natural paints which can be found online or in text books. Natural paints are starting to take preference in the construction industry on new builds due to their finish and lack of toxic chemicals which are found in oil and latex based paints.
Note: You should never paint your Cob walls with latex or oil based paints as it impairs breathability. Similarly, cement and other unnatural plasters should not be used.
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