Processing of

clay plaster


Why build with clay?

People have been using clay as a building material for thousands of years. To this day, it creates comfortable living spaces as an ecological building material.

It is becoming more and more a matter of course to ensure that the home environment is also designed to be natural. This is important for well-being, because people are staying more and more in enclosed spaces. The designed environment has more and more influence on people. With its many positive properties, clay gives our living spaces a climate in which we feel comfortable.

The advantages of clay

Clay plaster actively regulates the room climate

Due to the ability to absorb moisture from the indoor air and to release it again, clay actively regulates the air humidity. 

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Clay binds pollutants and odors

With the moisture, clay also stores odors and pollutants. He breaks them down and ties them in firmly. One gram of clay minerals has a surface area of about 800 m².

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Clay preserves wood 

The equilibrium moisture content of clay is so low that it always removes moisture from the wood. A perfect protection for the wood from pests or fungi.

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The primary energy of clay plaster is close to zero

The production of earth-moist clay is very simple and requires only less energy, the gray energy (primary energy) of earth building materials is low. Transport energy can still be saved because of its frequent occurrence. 

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Clay is a natural product

Clay does not need any chemical additives and is therefore ideally suited for people with allergies and people suffering from MCS.

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Clay can be used over and over again

The low primary energy consumption can be further improved by using it multiple times. Clay does not bind chemically and is mixed with water to make new building material.

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Clay is a pleasure to work with and live in

Using clay is stimulating and inspiring for the mind, and living in clay rooms is calming and relaxing.

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Clay can be stored indefinitely

Clay is thousands of years old and has been stored in nature for ages. Clay can be stored for centuries without spoiling.

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Clay has a great heat transfer

Clay in combination with wall heating is extremely effective in transferring heat. Compared to lime, you only need half of the installed heating pipe for the same amount of heat.

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Process clay plaster by hand

Earth building is relatively easy to learn. Fortunately, you start every clay wall or ceiling with a base plaster. This plaster layer is ideal for practicing and making first experiences with earth building.

In old clay houses, the clay walls and ceilings that we want to work on are usually so uneven that the first thing to do is to fill in the rough unevenness and holes in the substrate with clay undercoat plaster or clay universal plaster. A homogeneous layer is then created on the wall with the classic clay undercoat plaster. It can be processed or applied both by hand or by plastering machines. Good tools made of steel are helpful for applying by hand, but also for the following smoothing and compacting work.

to the fitting tools

Three-layer clay plaster

A good clay plaster always consists of three layers. The first layer is the undercoat plaster or base plaster. It is applied to stable and otherwise suitable substrates. It should compensate for unevenness, with it the necessary layer thickness is achieved.

In most cases, a fabric layer is embedded in the second layer. These reinforcement fabrics consist of either jute, plastic or glass fiber. Clay plaster on masonry made of mixed bricks, on reed plaster bases, on half-timbered walls, on bales of straw and on panel materials such as soft wood fiber boards or OSB panels with reeds absolutely need the fabric. The jute fabric - strengthened without plastic - is the ecological alternative to synthetically manufactured products, but requires a little more experience.

to the jute mesh

An undercoat plaster is usually used for the first two layers. When plastering panel material, the first undercoat plaster layer can be dispensed with. A layer of fabric can be applied directly to this with clay adhesive and reinforcement mortar.

Finishing work on clay plaster

After the clay undercoat plaster has dried, the topcoat plaster is applied. Depending on your personal taste and preference, this can be a clay fine-finish plaster, a clay topcoat plaster or a clay colored facing plaster. A topcoat plaster should be rubbed off, this compacts the structure and the plaster becomes stronger. After a cleanly executed job, there is no sanding.

If a topcoat plaster is processed with the sponge board, the use of two different sponge boards is recommended. On the first day you work with a very fine sponge board, after it has dried you go over the surface again the next day with a coarse sponge board and wash off the sand lying on the surface. The subsurface is once again slightly compacted and nicely stable.  

to the finer sponge board

The last layer of plaster can now be painted or finely finished. One possibility is surface treatment with a clay wall filler. These fine-grain earth building materials can be sanded, with a little practice you can achieve surfaces in Q4 quality.

Process clay plasterwith machines  

From a certain size of the area to be processed, the use of a plastering machine is worthwhile.

All kinds of plastering machines are available on the market, although not every plastering machine is of course suitable for every purpose. In general, however, any clay can now be plastered by machine, from coarse undercoat plaster to fine facing plaster. The advantages of using the machine? :

  • Time saving

  • Energy saving

The greater "dirtiness" of the construction site, the increased effort due to masking the adjacent areas and the greater logistical effort quickly pay off with larger amounts of clay. In addition to the large plastering machines, which can go so far in their functionality that they mix, convey and apply, there are of course also more modest devices, such as mixing machines and agitators.

to the mixers