Earthen plaster

The term refers to a clay plaster mortar made ​​of clay, which is used as a plaster for building surfaces both indoors and outdoors. The use of clay plaster is one of the oldest building techniques of humanity, as the building material widely used, readily available and is easy to work with. In Central Europe it is first detected at houses the Hungarian Körös culture.

As a natural material with favorable properties of the clay plaster has fallen into the center of attention of builders, architects and interior designers since the late 20th century. The use of clay plasters in the design of interior spaces and exterior walls produced by special application forms a decorative effect, such as a colored decorative plaster.

Species

Clay plasters can be distinguished according to their thickness, after processing, after the tool with which they are applied, or after their area.

• Tonputz layer thickness between 1 and 30 mm. Can manually ( traditionally applied with a trowel ) or machined. Thanks very creamy consistency processing is similar to the plaster. The only clay plaster, which can be processed as deposits plaster.
• When cleaning deposits the layer thickness is between 7 and 10 mm, and the plaster is applied with Shine or Hand and warped with plastering tools such as the trowel or grapeshot. Fields of application are full plaster and Tonputz.
• The base coat is used as a flush and is applied from 5 to 35 mm thick, rule strength is about 12-15 mm. Also, base plaster is machinable, so it can be applied before warping with a Shine. When using container products, the use of Under silo is possible.
• Fine plaster is a solid top plaster layer in thicknesses up to 5 mm, usually with additional binders such as Cellulose, casein, methyl cellulose, or gum Aribicum. The surface is rubbed or smoothed.
• Is attached Hand of spachtelputz in layer thicknesses of 1 to 2 mm. He is a decorative plaster. The contract is a so-called " Venetian trowel " used a special, slightly conical shaped trowel with rounded corners or a trowel Japan. Decorative plasters can be colored, pure white or dark gray, with or without additives, which cause aesthetic effects.
• Painting plaster is a decorative plaster, can be white, colored or even dark gray and is applied in a just 0.1 mm thin layer of glaze brush. Often the decorative plaster straw, vegetable fibers or stones are added to that set by the Free Wipe visual accents and additional binders such as casein, methyl cellulose or gum Aribicum.
• Mineral plaster is a special formulation of clay and special sands with good strength even without herbal additives such as chopped straw. He is machinable and silofähig. The processing times are shorter than for clay plasters with herbal additives. It is suitable as base and top trim. It can be applied by cleaners without special Lehmerfahrung. The surface can be left natural, be painted or wallpapered.

Components

Clay plaster is composed of clay, sand and silt ( very fine grit ). It cures by the particular structural properties of the clay alone by evaporation of water and adheres by mechanical claw to the substrate. The fine platy Clay pellets act as composite or as a "glue".

To improve the properties such as processability, ( tear) strength, adhesion, abrasion and moisture resistance and surface texture or for coloring the clay plaster finishing coats are mixed with different materials depending on the application. These include pigments; Minerals such as marble flour; Fibers such as cellulose, chopped straw or hay, cow or horse manure, animal hair; protein-containing substances such as whey, curds, animal blood; ( hydraulic ) binders, such as silicates, lime or cement.

In some arid regions of the subtropics of clay plaster is traditionally drawn over the entire outer skin of the house including the roof. To increase the resistance to the rare but often heavy rain, the clay, various organic ( fiber ) substances or nowadays also cement are mixed. In some regions of the plaster after the order by slurries or barrier coatings based on plants or by the mixture of tar is made weather-resistant.

Constructional Features

Clay plaster is water soluble. Outside, he is now subject to restrictions in rainy regions. Indoors, however, the clay has for its moisture-regulating properties has many advantages over conventional, cement- plaster.

The high bonding strength of the clay, which he already has as a raw material, in addition by the addition of vegetable starch and fiber material (straw, reeds, horse manure, cellulose) can be improved. As with other materials ( for example, lime or gypsum mortars, concretes ) provides a well-balanced particle size distribution of a tough, hard surface from a high strength. With appropriate processing, the use of clay plaster themselves in bathrooms outside the splash zone is possible.

Influence on the indoor climate

Basically, all wall coatings affect the indoor climate: permeable, ie " breathable " coatings performed kapillarleitfähig, that allow wall behind layers absorb moisture and release it again. In conjunction with that of the clay plaster ability to absorb a lot of moisture ( up to nine times more than gypsum), a climate buffer is on the wall, the moisture absorbs and releases it at low humidity. Clay plasters are available with these properties, in contrast to so-called " film-forming " surfaces such as latex paint and latex paint, which transmit little or no moisture in underlying layers.

The greatest influence on the ability of the clay plaster for the air cushioning effect, the surface of the plaster wall. The layer thickness of the clay is in the use of rooms of secondary importance, because more than 80 % of the moisture is bound first in the top two millimeters of mud wall. Only 10 mm are at " normal living behavior " for the " air buffer " effect relevant since the responsiveness of strong plaster layers ( > 20 mm) is too slow to respond to the ever-changing ambient humidity can.

Clay retains heat (depending on the amount of built-in ) and due to the high specific heat capacity are mud walls to compensate for temperature differences in the situation. The thermal conductivity is 0.47 ... 0.93 W / m · K.