Floor screed with expanded clay: features and technologies

For a person to live comfortably in a private house or apartment, it is very important to create the right microclimate. For this, attention is paid not only to the environmental friendliness of the materials of the dwelling itself and its ventilation, but also to thermal insulation. Some people mistakenly believe that the floor will be warm without much effort, especially if it is made of wood. Nevertheless, about half of the heat from the room can “disappear” precisely because of incorrectly or insufficiently insulated floors and roofs, which in turn leads to increased energy consumption and the creation of uncomfortable conditions in the room..

The expanded clay floor screed allows you to arrange floor insulation in any room, besides, knowing all the nuances of working with this material, you can safely carry them out yourself.

Material features

Expanded clay is a building material that is made from clay rocks suitable for these purposes. It is dried, crushed, and then sieved several times to separate it from other rocks and impurities. All these steps are important for the production of truly quality material. Then the raw material is brought to the required consistency with water, and balls of the required size are formed using special drums..

In the same place, they are fired in a special way in order to obtain an expanded mass. This is possible due to the high-temperature drying technology, which is accompanied by active gas evolution. Expanded clay balls have unique characteristics due to the fact that they are filled with air inside, and are enclosed in a dense shell on top.

Despite the abundance of modern insulation materials used for floor screed, expanded clay continues to be used to this day. However, not every type of this building material is suitable for these works.. The choice of a particular faction, as a rule, depends on specific conditions:

  • being near water;
  • the chosen method of installation (dry or wet);
  • required thickness of the thermal insulation layer.

The material made in accordance with GOST does not pose a danger to human health. At the same time, some manufacturers neglect these requirements and produce products according to technical conditions, which may differ significantly from the standards adopted by the state. Such expanded clay very often contains unacceptable impurities that can significantly increase the radiation background in a home and lead to disastrous consequences..

Therefore, before purchasing this building material, you should carefully read the documentation, clarify the manufacturer and product compliance with safety standards..

The grain size of the fractions is a parameter that can significantly affect the physical properties of expanded clay and its field of application.. Here are the main types of this building material:

  1. Granules – gravel. May have a minimum size of 20 mm and a maximum size of 40 mm.
  2. Expanded clay crushed stone with particle sizes from 10 to 20 mm.
  3. Expanded clay sand is obtained by crushing gravel into crushed stone and has particles less than 10 mm in size.

Only the first two materials can be used for floor screed, sand is unsuitable for these purposes. The fact is that the particle size is so small that it is not able to create an air cushion necessary for an effective thermal insulation device. Such a claydite-concrete mixture in its properties differs little from a standard concrete coating..

Advantages and disadvantages

Expanded clay floor screed does not lose its relevance due to environmental friendliness and availability of material. In an apartment or a private house, expanded clay is used for thermal insulation under floor coverings due to the following advantages:

  • Allows you to raise the floor level (especially in conditions of insulation of the subfloor in private houses and cottages) and keeps the cold from the ground.
  • Insulates reinforced concrete floors in apartments, under which there are unheated (non-residential) premises.
  • Perfectly insulates the room due to its porous structure.
  • With unevenness and differences in floor level in the room, it allows you to level the surface very cost-effectively, especially in comparison with concrete and ready-made screed solutions.

  • It is inert to the formation of mold and rot, since it does not contain a nutrient medium for pathogenic organisms, which means that you do not need to worry about increased dampness and dangerous fungal spores that can damage human health.
  • Does not create additional load on the floors, as it is a very light material.
  • It is not flammable, which means it can be used for underfloor heating. If a fire breaks out in a room with expanded clay floor, no harmful and toxic substances are formed in the combustion process. Also, in such a screed, you can easily hide engineering structures and electrical wiring..
  • Not afraid of temperature changes. Does not lose its properties at both low and high rates.

  • Long period of operation. According to some reports, expanded clay is able to retain its properties for 30-40 years..
  • For the device of expanded clay screed, special skills and complex tools are not needed.
  • Moisture resistant. The water absorption coefficient ranges from 8-20%.
  • Low cost and availability allows you to find this material in any, even a small town or village..

However, in addition to the obvious advantages, the floor screed, made of expanded clay, has some negative points.. Among them:

  • In most cases, the thickness of the expanded clay backfill is significant. As a rule, a screed layer of this material with a height of less than ten centimeters does not show the properties necessary for heat and sound insulation..
  • Dry screed, if moisture gets inside the expanded clay layer, it can significantly aggravate the microclimate in the room. Although the granules themselves are impervious to water, the concrete pavement on top may suffer..

Very often mold and mildew form on it, and the humidity level rises in the dwelling. In this case, the situation can only be corrected by a complete dismantling of the old screed and the installation of a new one..

Before giving preference to one or another material for floor screed, all the positive and negative points are carefully weighed. In the case of expanded clay, there are plenty of advantages, but the disadvantages are conditional and easily surmountable provided that all the necessary standards for carrying out work on thermal insulation of the floor are observed.


For floor screed in residential premises using expanded clay, including in new buildings, three methods can be used:

  • semi-dry;
  • dry (backfill floors);
  • wet (expanded clay concrete).

Each of these methods has its own characteristics and subtleties when carrying out work. But always pre-cleaning the sub-floor from debris and dust. If the floor has irregularities, then they are eliminated, and the old screed is also dismantled. For waterproofing purposes, bituminous mastic or special roll material is often used, which is overlapped on the floor. Its sheets are connected to each other using masking tape..

Semi-dry method

The semi-dry method is the only one that does not require scrupulous preparation of the floor for applying the screed. After cleaning up the rubbish, you can start working right away. If wires or communications pass under the floor, then they are insulated and pressed tightly to the base of the floor.. Semi-dry installation consists of two successive stages:

  1. First, the floor is covered with expanded clay. It is important that its level is 2-2.5 cm below the future subfloor.
  2. Then the floor is poured with cement mixed with water. After the granules have set together, the surface is additionally poured with sand concrete and allowed to dry well.

Dry method

The dry method is very popular, as it is the simplest, and does not require the purchase of cement. For the installation of such a screed, the previously prepared floor is covered with a vapor barrier film, and the necessary layer of expanded clay is poured onto it and carefully leveled using a level. GVL plates are laid on top.

Wet way

The wet method provides for the independent production of expanded clay concrete. You can also purchase ready-made mixtures, for example, from companies “Vetonit”. Buying a ready-made expanded clay mixture facilitates the work, however, it should be borne in mind that it hardens much faster than self-prepared expanded clay concrete.

The ratio of the components of a self-prepared solution is individual, it depends both on the quality of the concrete and on the characteristics of the room where the screed will be installed. The solution is poured between the pre-installed beacons and carefully leveled.

However, sometimes it is difficult to achieve a flat surface, therefore, an additional thin layer of concrete is often poured over such a screed, which levels the roughness of the subfloor..

Whichever method is chosen, it requires strict adherence to the stages and technology, and then you can achieve a high result.


Depending on the technology, the following tools and materials may be needed:

  • building level, better laser;
  • steam, hydro and sound insulation;
  • concrete or ready-made expanded clay-concrete mixture;
  • expanded clay;
  • water;
  • concrete mixer;
  • broom or construction vacuum cleaner;
  • trowel;
  • garbage bags;
  • shovel;
  • self-tapping screws;
  • glue;
  • drill;
  • vibrator;
  • lighthouses;
  • rule;
  • masking tape;
  • construction knife.

Before starting the installation of the floor screed in the chosen way, you must carefully prepare the room:

  1. The surface is dust-free, debris is collected in bags and taken out.
  2. Next, using a trowel, the old screed is dismantled.
  3. If the screed is laid on concrete, then the base is inspected for chips and cracks. Defects are closed with a cement mixture. It is impossible to achieve a good final result without carrying out repairs..
  4. Next, beacons are installed using a level. Subsequent actions depend on the method of screed using expanded clay.

After the end of the work (or after the required time), the beacons are removed, and the surface is leveled with concrete. The longest holding time is required for the screed, which was arranged with the wet method, while the dry method allows you to immediately proceed with the installation of the finish coating (parquet, linoleum, laminate).

Installation technology

Each of the three listed methods of floor thermal insulation using expanded clay has its own, unique stages and features.

When installing a screed using a dry method, the sequence of actions is as follows:

  1. A vapor barrier film is overlapped on the prepared floor. The sheets should overlap each other by 20 cm, and at the edges of the walls – 6-7 cm. The film is connected to each other with masking tape. The edges of the material on the walls are covered with edging tape.
  2. Self-tapping screws are screwed in at the top points of the floor surface, their tops are covered with cement mortar. Its quantity should ensure an even position of the rail, for this they are checked with a level.
  3. The lighthouses are installed on self-tapping screws. They can serve as smooth wooden blocks of a suitable size or a metal profile..
  4. A layer of expanded clay is poured into the prefabricated structure. It should not be less than 10 centimeters. The dry screed is leveled using the rule.
  5. A layer of expanded clay is carefully compacted manually or using a vibrating machine.
  6. The rammed areas are covered with GVL plates in two layers, as well as using penoplex. In some cases, the use of expanded polystyrene is justified. You can fasten them together with glue or self-tapping screws. If self-tapping screws were used, then the holes from them and the seams are carefully putty.
  7. The protruding edges of the film on the walls around the perimeter of the room are cut off. After that, you can proceed with the installation of the main floor..

When using the semi-dry method, the sequence of actions is as follows:

  1. Waterproofing is carried out using special materials or polyethylene film with a thickness of 2 mm or more. The joints are glued with masking tape. It is important that the edges of the waterproofing cover the wall by 10 cm or more.Lighthouses are installed using self-tapping screws, a level and wooden bars.
  2. A layer of expanded clay is filled up. At this stage, you should pay attention to the unevenness of the floor level. If they are present, they will be eliminated later in the process of applying the finishing screed. It is important to ensure that everywhere the level of expanded clay backfill is less than 2 cm in relation to the lighthouses.
  3. Cement milk is being prepared. To prepare it, sand concrete is brought with water to a homogeneous liquid state, reminiscent of milk in consistency. Pour a layer of dry expanded clay with the resulting mixture. After that, the surfaces are allowed to dry for a day..
  4. After that, the subfloor is poured with a screed. It consists of 3 parts of sand, 1 part of cement, water. The required amount of water is indicated on the packaging of the cement used..
  5. The concrete is leveled with a rule. The level of the screed should run along the edge of the beacons.
  6. After the expiration of the day, which is necessary for the screed to set, the beacons are removed. The places where they were located are filled with mortar and leveled. After 14 days, the covering is ready for laying the main floor..

Despite the fact that after two weeks the screed is ready for installation of the topcoat, it is not able to withstand constant loads. It is possible to use the premises without fear, including installing furniture, only after 28 days.

In the wet method, the screed also has two layers. Stages of work when using expanded clay concrete consist of the following steps:

  1. After laying the waterproofing, beacons are exhibited.
  2. A solution of expanded clay concrete is being prepared. For this, the following proportion is observed: three parts of sand, one part of cement and the required amount of water are added to eight parts of expanded clay. All components are poured into a concrete mixer and thoroughly mixed.
  3. The resulting mixture is poured over the beacons. “Underfilling” to the wall should be 2 centimeters.
  4. After a day, a finishing screed made of sand concrete is applied.
  5. After 2 days, the coating is ready for laying the main floor..

According to some technologies, you can not wait for the expanded clay layer to set, and immediately arrange the finishing screed.

Professional advice

Despite the simplicity of the technology of floor screed using expanded clay, you can make your life much more difficult, if you do not adhere to the recommendations given by professional builders:

  • If communications pass on the floor, especially electrical wires, they should be carefully insulated. Otherwise, short circuit and accident may occur..
  • Waterproofing cannot be neglected – it must be made without gaps and defects. Incorrect arrangement of this layer will significantly reduce the service life of expanded clay insulation and can lead to a violation of the indoor microclimate..

  • The surface on which the screed will be installed must be dry and free of debris and dust.
  • If it is possible to rent a vibrating machine, then you need to use it. This unit compresses the layers of cement and removes excess air from them, which reduces the density of the finished screed..

  • It is possible to add special improvers that strengthen the screed. They can be purchased at almost any hardware store..
  • The finishing screed is covered with plastic wrap until dry and moistened daily. Such “watering” is necessary so that the concrete does not become covered with cracks and does not begin to peel off from excessive dryness.
  • It is forbidden to put a load on the screed, made using semi-dry and wet methods, earlier than after 28 days..
  • Carefully follow the technological recommendations for time, depending on how much each of the layers of the expanded clay concrete screed dries.

By following these recommendations, you can avoid most of the problems that can arise both during the installation of the screed and during operation..

Expanded clay is one of the most demanded materials, which, despite the abundance of more modern building materials, does not lose its relevance. A do-it-yourself floor screed using expanded clay allows you not only to save money, but also to improve the indoor climate. One of the main conditions for success is the correct choice of material and method of floor insulation.. Correctly arranged thermal insulation will last for more than a dozen years and will reliably protect the flooring from dampness and mold, create a comfortable temperature and humidity in the house.

For more information on how to make a floor screed with expanded clay, see the following video.

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