Type of concrete for screed warm floor

Care of the damp screed

After the concrete layer is poured, the screed requires care. The temperature in the room must be kept at least 5 degrees above zero. Do not allow the screed to dry out. A day after laying it is covered with plastic film. About a month of concrete to moisten from time to time. The strength of the concrete depends on this. Begin the installation of the water loop underfloor heating can not begin earlier than 28 days. All this time in the pipes should maintain working pressure, but you can not turn on the heating.

How to make a warm and light screed from familiar materials

The use of cement-sand screeds for leveling the floor slab can lead to increased pressure on the interfloor plates. In order to avoid overloading it is worth using a lightweight material. monolithic polystyrene foam concrete. It is made with cement and polystyrene. Mixture of these components allows you to get polystyrene concrete floor screed, quite warm, lightweight, resistant to cracking and shrinkage. Such properties are provided due to the characteristics of foamed polystyrene granules. And the density and weight of the resulting thermal screed can vary depending on the conditions of use by changing the proportions of its constituent materials.

And in order to make the base faster use the ready mix Knauf UBO. This is a dry building mix based on special cement and polystyrene granules as a filler. The permitted thickness of the layer from 3. 30cm.

Polystyrene foam coatings are currently considered one of the most popular. And the main reasons for this are the following advantages of warm screed from monolithic polystyrene foam concrete:

  • increased service life in comparison with most other polymer materials;
  • good thermal parameters, allowing to get a comfortable microclimate in the room even without the use of additional insulation;
  • environmental safety obtained by using only food polystyrene in the manufacture of the material poured in cement.

In addition, among the advantages of foamed polystyrene flooring is the ease of making it. Pouring light screed for the floor can be performed directly at the site and in almost any conditions. over, the size of the unit for mixing does not exceed 0.8 m in width, and the weight. 100 kg.

To the disadvantages of the resulting floor covering can be attributed only two characteristics of the material. its relatively high price. If you buy a ready-made mixture, then a 25 kg bag of UBO.(A fairly large bag) will cost about 450 If the consumption of dry mixture per 1 sq.m with a layer thickness of 30 mm.17.6 kg.

With lightweight pours, an additional cement-based floor screed must be applied in any case.

How to prepare the mixture

To prepare high-quality concrete mortar, it is better to take coarse sand. Small grains of sand contribute to the formation of cracks in the screed under the influence of constantly changing temperature. Such a defect is almost not repairable, while reducing the heat output of the system and lowering the temperature in the room.

To make the screed was performed qualitatively, it is necessary to prepare the mortar correctly. To do this, you need to combine the sand and cement in dry form, mix them thoroughly, and then add water. Liquid is added to the dry mixture for screed floor heating in small portions, stirring well after each addition. The amount of water depends on the consistency required for the mortar. It is very important that it does not spread over the surface of the floor, and had sufficient plasticity. Proceed to the pouring of the screed can only be done after the necessary plasticity and homogeneity of the solution.

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Wet screed is popular among private and professional builders. In the process of operation began to reveal not only the advantages of such a screed for underfloor heating, but also its disadvantages. In particular, the following has become known:

  • The screed takes a very long time to dry, complete drying is achieved in 28 days. This is due to the fact that the mortar contains a large amount of water.
  • In the process of filling screed is not ruled out the formation of voids, which are almost impossible to remove, as sealing can damage the heating elements of the floor heating.
  • Screed drying is always accompanied by cracking. Partially solve the problem by reinforcing with a metal or polymer mesh. However, small cracks are always present on the surface.
  • Leveling screed refers to time-consuming processes, it is necessary to install beacons and use a rule. After the mortar for screed warm water flooring a little dry it is necessary to grout the recesses and cut off the excess mortar.

Concrete grade for floor screed: what grade of concrete is better to use for screed, tips on making it with your own hands

Concrete for floor screed is most often used as a base for finishing coatings. Only in garages, outbuildings and industrial plants can you find this material as the main surface coating.

To increase the strength of concrete screed, two special construction techniques are used.

    Reinforcement. Depending on the calculated loads, concrete is reinforced with metal mesh with a wire thickness of 0.5-1.5 mm, the surface of the wire can be covered with a layer of zinc with a thickness of at least 20 microns. Such a grid is not afraid of corrosive processes and serves for several decades without loss of the original strength indicators. If the concrete floors are exposed to significant forces, the building reinforcement of periodic profile Ø 8-10 mm is used for reinforcement. The number of reinforcement layers from one to two, the distance between the bars and the depth of their embedding take into account the maximum design loads.

Material for screed

If we consider the option of traditional screed for water heated floor, the solution includes cement and sand, diluted with a certain amount of water. The most important thing in this situation. to fully comply with the proportions of each component in order to obtain a truly high-quality mortar for screed warm water floor. This, in turn, will contribute to obtaining a protective layer for the entire system.

It is very problematic to obtain the necessary mortar for screed warm floor, if you do not do without such modern means as plasticizers or additives that improve the quality of the filling. In addition, the surface above the pipes should have the same thickness over the entire area of the room. These components help to get rid of excess water, give the mass of plasticity and provide a homogeneous composition of the screed for water heating.

Depending on the amount of water, screeds for water heated floor are divided into:

  • Liquid. They are the most popular. Uniform structure above the pipeline is obtained at the expense of uniform filling of available voids in the base.
  • Semi-dry. The amount of water in the mortar corresponds to a minimum parameter. It will not be superfluous in this case, instead of a layer of reinforcement, add a special additive. fiberglass. It is not inferior to metal mesh in terms of properties, but gives better qualities to the finished mortar.

Screed for underfloor heating: the required thickness and pouring technology

The project of a warm floor most often involves pouring a protective layer of concrete. In order for the screed for underfloor heating to effectively perform its functions, it must be properly mixed and installed in full compliance with the system parameters. As you know, this is the main “heating element” of a warm floor, whether it is electric or water, so its quality largely determines the reliability of the entire structure.

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The plaster under a warm floor in terms of volume and the list of necessary works, as a rule, is not very different from the general scheme of the device of the rough floor under a decorative coating. However, the scope of application imposes certain restrictions and additional requirements for its composition.

Semi-dry screed floor on a warm floor

For water and electric heated floors the semi-dry method of formation of a protective layer is used.

Semi-dry screed method. A small amount of water is used to make

It involves the use of the following components:

  • Cement grade M300 and above. 1 part.
  • Coarse sand, cleared of impurities. 3 parts.
  • Fibers, representing a fiber, introduced in an amount of 400-600 g per 1 m³ of mortar.
  • Water injected to a slightly wet consistency of the composition.

Semi-dry mix has advantages and disadvantages. The positive aspects of the semi-dry mixture are:

concrete, screed, warm, floor
  • accelerated curing;
  • increased strength characteristics;
  • Little shrinkage;
  • absence of cracks;
  • resistance to temperature fluctuations.

Disadvantages associated with the peculiarities of the laying technology include:

  • stiffness of the composition, which is difficult to stir;
  • The need to protect the semi-dry mixture from moisture absorption;
  • presence of voids caused by uneven compacting.

Installing underfloor heating

One of the key components of the system pipes and their fixation system. There are two technologies:

  • Dry polystyrene and wood. On the system of foamed polystyrene mats or wooden plates are laid metal strips with molded channels for laying pipes. They are necessary for a more even distribution of heat. Pipes are inserted into the recesses. The top is covered with rigid material such as plywood, OSB, GFB, etc.д. A soft floor covering can be laid on this base. Installation with tile, parquet or laminate flooring is possible. Wooden underfloor heating system
  • Working with screed or so-called “wet technology. It consists of several layers: insulation, fixing system (tapes or mesh), pipes, screed. Top of the pie after the screed has set, is laid the floor covering. If necessary, under the insulation lay a layer of insulation. so as not to flood the neighbors. There may also be a reinforcement mesh, which is laid over the floor heating pipes. It redistributes the load, preventing damage to the system. An essential element of the system is a damping strip, which is rolled around the perimeter of the room and is laid at the junction of the two circuits.

Both systems are not ideal, but it is cheaper to install pipes in the screed. Although it has a lot of disadvantages, it is because of lower cost more popular.

Which system to choose

In terms of cost, dry systems are more expensive: their components (if you take ready-made, factory-made) cost more. But they weigh much less and are quicker to put into operation. There are several reasons why you should use them.

First: The high weight of the screed. Not all foundations and floors of houses can bear the load created by a water heated floor in a concrete screed. Over the surface of the pipes should be a layer of concrete at least 3 cm. If we consider that the outer diameter of the pipe is also about 3 cm, the total thickness of the screed is 6 cm. The weight is more than significant. And on top is often more tiles on a layer of glue. Well, if the foundation is calculated with the reserve it will hold, but if not. problems begin. If there is a suspicion that the ceiling or foundation can not withstand the load, it is better to do wooden or polystyrene system.

Second: low repairability of the system in the screed. Although when installing floor heating circuits it is recommended to install only complete coils of pipe without joints, pipes are occasionally damaged. Either it was hit with a drill during repair, or it broke because of a defect. The place of damage can be identified by a wet spot, but to repair it is difficult: have to break the screed. It is possible to damage the neighboring hinges, so the damage area becomes larger. Even if you can do it accurately, you have to make two seams, and they are the potential places of the next damage.

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The process of installation of the water underfloor heating

concrete, screed, warm, floor

Third: the commissioning of screed floor heating is possible only after the concrete gains 100% resource strength. It takes at least 28 days. Before this period it is impossible to turn on the floor heating.

Fourth: you have made a wooden floor. The pulling itself on the wooden floor is not the best idea, and the screed with high temperature. The wood will quickly collapse, collapsing the entire system.

Causes are serious. Therefore, in some cases, it is more appropriate to use dry technology. All the more so that the wooden water heated floor with their own hands is not so expensive. The most expensive component is metal plates, but they can also be made from thin sheet metal and preferably aluminum. It is important to know how to bend, shaping grooves for the pipes.

Warm floor / Теплый пол

Option polystyrene floor heating system without screed is demonstrated in the video.

Finish pouring on the TP

If the rough screed has dried, it’s time to move on to the next steps:

  • installation of thermal insulator. Insulating material is mounted only on a clean base (best to vacuum it). Thermal insulator can be a cork substrate, foamlon, polypropylene, aluminum foil or metallized lavsan film. To fix it, you can use tape, dowels and glue.
  • Laying of the dampener tape. Damper tape protects concrete from cracking due to temperature jumps. Fixing area: along the perimeter of the room and between the contours of the floor heating.
  • The laying of underfloor heating. Pipes should be checked for leaks (especially in the bends), and if the cable. to ensure grounding.
  • Reinforcing. Reinforcing mesh can be placed under the pipes, above them, or in both places at once. The bottom metal mesh is easily attached to the pipes during their installation, but it does not provide screed reinforcement, unlike the upper one. If the concrete is of high quality, this part of the job can be omitted.
  • Pouring of the finishing screed. Before proceeding to the last step, you must always check how well the heating system works. Screed must be poured in one pour at temperatures above zero zero. Carrying out partial pours are allowed only in the rooms with multi-level floors. The process of concreting begins from the far side of the room and ends next to the door.

After the end of the pouring it is recommended to make a few pierces in the coating with a metal spoke or similar tool. This will prevent the formation of voids.

During the next week the surface of the concrete should be moistened with water 2-3 times a day. This will keep it from drying out during the curing process.

The thickness of the finishing layer can be from 3 to 7 cm in a private home, and in the industrial area. 10 cm.

If there is water underfloor heating, the height of screed above the pipes should be 3,2-7 cm.

Attention! If you can not make the poured concrete layer thicker than 3 cm, it is better to use self-levelling mixtures, or mix cement mortar with plasticizers.

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