Clay earth – a building tradition with a guarantee for the future

Since we associate clay earth primarily with historical buildings, it makes sense to see clay earth as a product for renovation and landmark preservation. In fact, the recyclable material is ideal for preservation of historical landmark buildings.

Fascinating fact: Clay earth can be recycled again and again. Even after hundreds of years, ancient earth building materials can be removed from the structure, soaked with water and reused. This is only possible with clay earth.

Clay earth as a building material is more relevant today than ever. Thanks to its ecological and healthful building-friendly advantages, it fulfils any expectations you may have for your home. At the same time, clay is extremely versatile in design, so that any desired look can be achieved using it.

Clay earth can be combined well with other building materials such as wood, but also masonry, plasterboard or concrete. It can therefore be used for renovations or in conventional new builds.

If you want to build an entire house out of clay earth, you have to take into account that clay is sensitive to moisture. For this reason, areas such as facades or elements close to the ground that could potentially come into contact with moisture must be specially protected. This can be ensured, for example, with a large roof overhang, wooden cladding or a barrier layer between the foundation and the rising wall.

Like all mineral building materials, clay earth can only absorb pressure but not tension. Therefore, clay earth was and is primarily used as a building material in walls. Floors can also be made from clay earth and ceilings covered with it.

Clay earth occurs in different forms throughout an entire wall structure and takes on specific tasks in each:

Building construction

• Clayboard panels: Clay drywall panels are a modern invention. For this purpose, clay earth is combined with fibrous aggregates. As usual in drywall construction, they are a screwed onto a frame made of wood or metal.
• Clay in half-timbered construction: In addition to clay-earth bricks, the compartments can also be filled with branches, wooden sticks (stakes), or natural stones, which are then plastered with clay earth.
• Clay bricks: Clay-earth bricks are usually air-dried. They are built into non-load-bearing interior walls or used to fill the compartments in half-timbered buildings. When constructed to have particularly high stability, they can also be used as masonry for load-bearing walls.
• Rammed earth: Here, moist loam is placed in a formwork in layers and compacted. A compacted clay-earth wall with characteristic horizontal stripes is created.

Thermal insulation

Clay earth has a high thermal mass, that is, it is very good at storing heat. Its heat-insulating properties can be further improved by adding various other materials such as chopped straw and pumice. Then it can also be used as plaster or clay brick for interior insulation.

Interior plaster

Depending on the wall structure, clay earth can be used as a base and/or top plaster. It adheres to a variety of surfaces – including conventional ones such as concrete or plasterboard. Clay plastered walls are ideal in combination with wall heating. The heating pipes or hoses are covered by the plaster. Clay earth stores the warmth and releases it evenly into the room – how comfortable!

Fascinating fact: Due to their heat storage capabilities, walls made of clay earth or clay plaster can play an important role in home energy regulation. During the cold season, passive solar energy provides heat, brought into the rooms through the windows, which is stored and later released. In summer window shades prevent excessive heating while clay-earth walls keep interiors cool.

Surface coating

Clay earth is also ideal for the design of the wall surface. There are two options here:

• Design plaster: The plaster made of earth and clay is applied to the wall in a 2 mm thick layer. The clay serves as a binding agent and colouring agent.
• Clay paint: Applied like any wall paint, but breathable and free from any solvents. This means that the good, healthy properties of the clay-earth layers underneath are retained one hundred percent.

DIN standards for earth building materials were established in 2013. They offer building owners and contractors liability protection.

Clay designer plasters and clay paints can be used in the same way as conventional products. Any desired style can be achieved. The colour and unique surface of the clay also serve to stimulate creativity.

• Natural surface: Even as an untreated surface, clay earth has a natural aesthetic and feel – for example, as clay earth masonry or rammed earth. In the past ancillary and storage rooms were left in their natural state and are now liked for their charm.
• Colours: Clay earth has a natural colour, in and of itself, as a result of the type of clay used as a binding agent. This property can be made use of. Clay paints or clay plasters can be produced in many different colours by adding different types of clay.

Fascinating fact: The manufacturer CLAYTEC offers its clay designer plaster and clay colours in 146 earth tones – all made naturally by adding different clay.

• Surface textures: Various different textural effects can be achieved by adding a wide variety of materials such as sand, straw, glitter or even herbs.

Fascinating fact: In the Kolumba Diocesan Museum in Cologne, built in 2009, achieving the uniquely smooth surface and the subtle shine of the 2 mm thick clay plaster was possible using Japanese trowels and polishing the walls with water and milk curd.

• Moisture regulating: Clay consists of the finest silicate particles layered throughout the material. Water can be stored in the gaps between these particles. This is what gives clay earth its good moisture-regulating properties. For indoor and living spaces, this means that when the humidity is high, water is absorbed from the air. When humidity drops, this water can be later released. This not only keeps the humidity constantly within a comfortable range, but water on the wall surface and ultimately mold formation are prevented.

Fascinating fact: A study from 2002 by Holl and Ziegert shows that a highly absorbent clay-earth plaster (of 1.5 cm thickness) can store up to 70 g of water per square meter of wall surface.

• Air purifying: Along with water vapour, pollutants, fine dust and odour molecules can also be absorbed. This makes clay earth ideal for modern, open floor plans.
• Heat-storing: As a building material with high thermal mass, clay earth is a very good heat store and can, release solar heat absorbed during the day in the evening, reducing the need for additional heating.
• Free of harmful substances: clay earth is a purely natural mineral-based product. It works without chemical additives. Special properties and textures can be achieved with the addition of other natural materials.

In order to get the benefits, the entire house does not need to be made of clay earth. Depending on the building project and requirements, clay-earth products can be combined with other materials.

• A surface plaster made of clay may be sufficient for achieving a pleasant room climate.
• A wall made of rammed earth can be a heat store as well as a design highlight in the room.
• Those who want to build sustainably and healthfully or who are renovating with a focus on historical preservation should use as much clay earth as possible.