Clay is a natural rock or soil material widely used for construction for many centuries worldwide. The material can be extracted easily without depletion of the natural resources. Clay materials are non-toxic and efficient with good thermal insulation properties. Clay building materials’ lifespan is about 150 years. Bricks, pipes, roofs and facade tiles are the most common materials made out of clay. The versatility of the clay shapes and colors create different design opportunities.

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Clay is a natural rock or soil material consisting of clay minerals such as kaolinites or smectites, also small amounts of quartz, metal oxides, and organic matter. The formation of clay is relatively slow occurring due to the rocks’ weathering and erosion. The clay is easy to extract from the ground. The shape can be changed only by adding water and additional ingredients such as sand or straw for higher strength. 

Clay materials have an ancient history in construction. Almost half of the global population uses buildings with clay as the main part of its load-bearing structure. Among the most common clay construction products bricks, terra-cotta facade tiles, drainage pipes, and roofing tiles. The clay is also used as a substance of composite materials such as adobe, cob, rammed earth, ceramics, mortar. 

The clay provides great thermal insulation and thermal mass. Clay materials are durable, fire-resistant and have a unique rustic appearance. 

 

Clay types used in construction

  • Mudwall clay. The combination of earth mix and straw with the width from 15 to 55 centimeters. 

  • Turf clay. Clay blocks are used alone or with stone to build the walls typically in a herringbone pattern for higher strength. 

  • Brick clay. Low-grade clays rich in silica, alumina, calcium, magnesium are used for the bricks production. 

  • Fired clay. Bricks, tiles, pavers and other versatile clay products are manufactured today using new technology but achieving a hand-made heritage look. 

  • Porcelain clay. High kaolin content creates a pure white clay product, which is durable, strong, and stretchy.

  • Earthenware clay. Creek beds contain fine-grained clay available in brown, orange and red colors. 

  • Burnt clay. The ancient type of material is produced by pressing wet clay into molds and firing in kilns to dry. 

  • Sand lime clay. Sand, fly ash and lime bound together by a chemical reaction create the type of bricks.

  • Light straw-clay. Clay coats the straw producing the blocks or walls with outstanding insulation characteristics. 

  • Residual clay. Clays with pure chemical composition cover the top layer of the rocks. 

  • Vitrified clay. High amounts of carbonates of calcium and magnesium and iron oxide form the smooth-surfaced clay products, which cannot withstand high temperatures. 

 

Maintaining and repairing clay structures

Just as with any building but with clay structures, in particular, prevention from water damages techniques should be used. Building clay structures on plinth stonework to reduce dampness from the ground is a common practice. A French drain is a relatively effective solution to stop decay at the base of the wall. In case the decay is already present, rats and mice sensing the food source can damage the clay structures. Vegetation next to the clay building can spread and penetrate the walls and the base. 

Before repairing any building containing clay materials, an inspection of the structure and surrounding area should be held. If some parts are deformed, the replacement and the cause of destruction eradication will be a better solution. In the case of the replacement of the section, finding a material to match the original is significant. Clay block or patch repairs appear to be a suitable solution in many situations when replication is not possible.

 

Clay materials - video