Screed height for underfloor heating

Suggestions for the device

There are minimum parameters for underfloor heating screed, the level of which begins from the upper edge of the pipe system. This figure starts at 30 mm. When using a pipe with a diameter of 16 mm for floor heating, you will need to make a screed layer of at least 50 mm. But for this, too, certain requirements and conditions must be met. After all, the minimum limits for the priming layer can only withstand minor loads from furniture and people walking around the room.

Uneven heating of the underfloor heating can be caused by certain factors. If you make a minimum pouring screed warm water floor and choose a large pipe laying on the base of the floor, the surface will not be able to warm equally over the entire plane. This will be clearly visible if you use a thermal imaging camera in the work of the underfloor heating. It will indicate those areas that practically do not receive heat.

Almost every specialist will tell you that you will need to make a screed of at least 70 mm from the base along with the piping to get a really high quality. Consequently, over the pipes themselves heating system should create a screed with a thickness of at least 20. 30 mm. In this case, the base will be able to withstand the load even from placed bulky furniture. The distribution of heat over the entire surface will be ideal.

Some believe that the fact that the layer of filling will be large, it will be necessary to increase the power of the system of warm water flooring. In this case, you may be faced with inertia, which is a disadvantage. The resulting structure will warm up longer in time, just as well cool down. This will lead to the fact that it will not be realistic to use automatic sensors to adjust the temperature level inside the room.

How to calculate the thickness of the concrete screed over the water underfloor heating

The thickness of the screed under the floor heating depends on many factors, but it must be the same across the entire surface. Installing a waterborne floor is performed in several stages, where the mandatory is the organization of waterproofing and thermal insulation, laying reinforced mesh, pipes and screed. The last stage of the work requires special responsibility and adherence to technology, because it depends on the protection of the heating system and surface preparation for laying the final, decorative coating. It is the appropriate thickness of the screed provides strength and uniform warming of the floor.

Thermal insulation of the basis

Before installing the heating system, it is necessary to perform insulation of the base. Thermal insulation layer will protect the water circuit from loss of heat escaping into the basement or foundation of the house. As an insulator is used:

Listed materials are highly resistant to mechanical stress, resistance to moisture and temperature fluctuations. The thickness of insulation is 30-50 mm, it is laid on a waterproofing layer of polyethylene film. A blanket is laid with an overlap on a clean dry basis, it will be a protection for insulation against getting wet. Thermal insulation plates are laid butt butt joints, the joints are sealed with glue or blown with foam, and the excess is cut off.

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Foam-foil or a similar cloth reflective insulation is placed on top. A layer of aluminum foil is directed upwards, this will reflect most of the heat back to the side of the room. The joints of foil insulation are glued with a special adhesive tape. Foam foam will protect the insulation from the aggressive effects of concrete. Metal reinforcing mesh is laid over the thermal insulation. This element evenly distributes the high load from the water circuit system and the concrete structure.

Types of screeds and their thickness

Experts on laying floors advise the use of cement-sand mortar for pouring. It will make the base warm, strong and durable. It is necessary to take into account some nuances in the pouring itself and the method of preparation of the mortar. Concrete coating is made of cement, sand and water. The classic and optimal thickness will be at least 4 cm.

If necessary, the floor and its height can be reduced by adding special materials. One of these is considered a plasticizer. It will reduce the height and make the material more plastic. The use of plasticizer is recommended by many experts, as it allows the cement-sand mortar does not crumble and do not collapse during drying and further operation.

There is another important point. If the area of the pour is large, fiber, basalt or polypropylene should be added to the mortar. Fibre improves the quality of the mortar, the coating is laid in a more even layer. It is accepted to be used instead of steel mesh, if we are talking about large areas. The screed will have such a characteristic as increased strength and durability.

The substrate will not crack or delaminate in the future. As a result of adding additional materials, the thickness of the floor may decrease. However, the height of the floor pipe coating in any case will not be less than 4 cm.

In the arrangement of the base of the water floor, experienced builders act as follows:

  • A special substrate of extruded polystyrene foam is placed on the rough base.
  • On it is mounted lavsan film (vapor barrier).
  • It is closed with a layer of foil.

The last of these components is necessary to distribute heat evenly over the entire floor in the apartment.

screed, height, underfloor, heating

A good substitute for such a substrate. foam or extruded polyethylene, which is not inferior in its characteristics polystyrene foam. The distinctive features of the latter include a very low thermal conductivity, in which it is inferior only to mineral wool coatings. Screed for water underfloor heating on top of the insulation layer turns into a heating monolith of a large area.

Since polystyrene, as well as polyethylene can withstand heating up to 900 degrees, water pipes are laid directly on the floor foundation without harming the insulating material. In the manufacture of warm floors on the interpanel floors are taken polystyrene foam plates with a thickness of about 20-30 mm. On the first floors of buildings located directly above the foundation, it is allowed to use foam plastic as a base. plates with a thickness of at least 100 mm will be required. Other materials that, according to SNIP, are allowed to use as a substrate:

screed, height, underfloor, heating

The choice of a particular material is determined by the current condition of the subfloor and the type of floor covering to be laid on it.

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The construction of a warm water floor

Most often, the structural composition of the floor in the jargon of builders called pie, it consists of layers of different types and kinds of material. The number of layers depends on the finish coating, climatic conditions, which differ in different regions, and a number of other factors:

How to Lay Underfloor Heating in a Screed

  • the type of substrate for the floor;
  • anticipated maximum load;
  • The level of the desired air temperature;
  • The permissible value of the heat carrier heating.

After studying all these aspects, you will be able to determine exactly what the thickness of the water type heated floor for a particular room. In general, the technological cut of the entire pie consists of seven layers, not counting the base, which initially must be solid. That is, it is usually in the form of a concrete slab, beams with floors, or ground. In the latter case, it is necessary to make a layout, and on the floor to lay a rigid sheet covering, for example, a double layer of LSU or GFB.

Installing the floor begins with waterproofing against water leakage in case of an accident or protection against groundwater (on the first floors of private homes). Then comes a waterproofing layer, most often in the form of foam polystyrene, to protect the energy loss of the coolant down. The next step is to reinforce the base for laying pipes. For this purpose it is used a metal or plastic rod, so that the pipes do not lie directly on the thermal insulator. Just use special cork mats with a precise fixing coil piping, for example a good and very convenient mats under the floor heating with bosses are at Rehau.

On the fourth technological layer is the water pipeline, laid in accordance with SNIP and the specific configuration of the room. The fifth layer is always a cement-sand (in some cases concrete) screed. Concrete screed, differs from the standard cement base by the presence of gravel or crushed stone in the ready mix. It is good if there is an opportunity to fill it with self-levelling mortar, otherwise you will need to expose the system of beacons on the level of the horizon. It fills all the space between the pipes and is sure to rise above them by a few centimeters.

And lastly, it was mentioned above that the pie has seven layers, but taking into account the final coating, there can be six, for example, under the ceramic tiles there is no need to lay a substrate. Whereas for laminate flooring it is necessarily present.

Maximum limits

No standards in the pouring of screed to the maximum is not provided. Technologically it is possible to arrange it to a height of 10-15 cm. If you do a layer of more, then it will not bring any efficiency. All the work carried out will be meaningless. But such a screed can be performed only in exceptional cases. Such situations may include the following:

  • If the layer to be arranged acts not only as a filling screed, but also as the foundation of the structure.
  • Installing the concrete floor in the premises with significant loads (garage).
  • The installation of screed on problematic soils, which is more suitable for private homes.
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If the floor bases have significant height differences, then some performers decide to do as much pouring as possible to bring everything to the horizontal position. But there is no expediency in it. It is best to make a preliminary backfill with dry materials (expanded clay), and then pour the solution. Such actions will save time on the work, as well as funds for materials. True, this is best done before the device water-heated floor. Heat pipe requires a flat surface for even distribution of heat over the entire floor substrate in the room. If there are large protrusions over the surface, they can be knocked down at all with a hammer or other equipment.

A large amount of poured concrete will be wasted. If we have a room of 10 square meters, and the screed layer is only 100 mm, it will take at least a cubic meter of concrete, and this is unreasonable costs.

There may be other difficulties with a thick screed over a water heated floor:

This all suggests that you should choose the optimal thickness of the screed for a warm water floor, so that all the characteristics of the system appeared and were well maintained throughout the life of the.

Screed for a warm floor: the subtleties of doing it with your own hands

Making a screed. one of the most important steps in the construction of a warm floor with their own hands. To this work should be approached with maximum responsibility, because of its quality depends not only on the appearance of the future floor. The screed for underfloor heating has several important functions:

  • protects the heating system from mechanical damage, and in the case of electric underfloor heating, also from the air;
  • Acts as a floor radiator of an impressive area, distributing heat from the heater over the entire surface of the floor and heating the entire space of the room;
  • it serves as a level surface for the final floor covering.

The difference from the usual screed

Conventional screed is somewhat different from the screed for a warm water floor. The fact is that in the latter form of it must necessarily be arranged expansion joints. Even in rooms with a small area of up to 10 m 2 they must be present. In addition, a cushioning strip must be arranged, which is laid along the bottom of the wall. This is all necessary to compensate for the thermal expansion of the concrete screed during the operation of the warm water floor system.

For large areas of the premises, the joints are also additional. Here, in addition to the tape, the function of compensation is also thermal insulation for the walls. In this case, the thermal insulation must have a thermal repellent foil.

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