Cob

The cob is raw a monolithic constructive ground system compacted in a formwork (Banchage). The ground is ideally gravelly and argillaceous, but one finds cob constructions realized with fine grounds. The ground can be amended (or stabilized) using lime, of Ciment, more rarely of other products.

The cob walls not covered with rough coat still let see the mortar beds protecting the successive stages from the construction of the walls by their helped inhabitants their neighbors, thus measuring the duration of the work of construction.

History

The cob is an old technique, which knew an renewed interest in the western world following work of François Cointeraux (17th century) on the subject. Its works were translated and diffused in the whole world. In France, one finds a great quantity of rural cob buildings dating from, in the Rhone-Alps area: Isere, valleys of the the Saone and the the Rhone, Bresse, etc But know-how almost disappeared there, in spite of an renewed interest for the material ground with the exceptional ecological assessment (see the recent buildings in North-Isere built by Germes of Ground ).

Geographical distribution

The cob is also widespread with the Morocco, in the buttresses of the the Himalayas, in China, South America. It is always used there in traditional forms. The technique is success in contemporary uses (but cob is almost always strongly stabilized with cement) in Australia, in the south of the the United States, like in Germany, Suisse and Austria.

Contemporaneity of cob

Contemporary architects and plastics technicians using cob: Rick Joy, David Easton, Martin Rauch, Kengo Kuma (it uses a type of cob baptized Hanchiku ).

Pathology

The cob is an alive material i.e. it breathes, absorbs and restores the air/ambient moisture. It may be that during the life of a cob building, this concept was forgotten from where appearance of certain disorders: blown coatings, traces of Salpetre…

Puffed up coatings

For reasons of esthetics or praticity (less dust), a coating was applied to the walls of a cob construction. However, after a few years, this coating is “puffed up” (taken off) in several points. That comes owing to the fact that the coating blocks all “breathing” of cob. It is thus important to avoid the application of any watertight facing (containing cement for example) and to privilege coatings containing lime slightly hydraulic or of raw ground.

Cover with salpetre

Many cob constructions, in particular in theDauphine one, were built without low flagstone, with very the ground. This technique had the advantage of allowing the moisture contained in the grounds to be able to evaporate freely. The construction of a pavement force moisture to be gone back thereafter to the level of the walls from where appearance of Salpetre.

See too

Related articles

External bonds

  • craterre-EAG
  • Akterre

Zh-yue: 夯土

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