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Laying the floor heating cable in the screed

laying, floor, heating, cable, screed

How to install the Thermoscreed In-Screed Loose Wire Heating System

Preparatory work

Before you begin installing the heating elements of the underfloor heating, you should consistently perform a few very important steps:

  • Determining the location of the thermal regulator. It is fastened like a normal switch. The best distance to the floor is 30 cm. Below there is no point in installing it. Besides drilling a hole in the wall for the thermoregulator, it is also drilled a hole perpendicular to the floor, where the power wire and other wires in the braid will be placed.
  • Prepare the floor base. Remove all debris and dust, carefully level the surface. There should be no pits and drops. When making the alignment, the thickness of the screed under the electric floor heating is not less than 30 mm. Otherwise the screed will crack. Prior to spreading the solution on the surface a layer of primer is applied. In addition, the areas where the furniture will be located, as well as marked indentation from the walls to the heating elements, which should be at least 50 mm.
  • Insulation layer. It allows to reduce the heat loss by about 30%. Installing insulation can be done not only vertically, but also horizontally. For vertical insulation, damping tape is used, as well as polystyrene sheets, the width of which is 15-20 cm. Heat loss will be reduced through the exterior walls in the room. As for horizontal distribution, it is laid on a prepared concrete base. The thickness of the sheets is usually at least 20 mm.

In the presence of a room with a high level of humidity, an additional waterproofing layer is arranged.

stage. the pouring of the screed

Installing electric floor heating in the screed is done when using cable or heating mats. In the case of a film floor, installation is carried out without a screed.

For the device of electric flooring in the screed is applied:

  • concrete screed. Classic mortar for concrete screed consists of 4 parts sand, 1 part of cement M400, 0.5 parts water. When using cement M200 the ratio will be 2:1. To increase the elasticity of the mortar, plasticizers (1%) can be added to it. The advantage of the plasticizer in the cheapness, disadvantage in the long period of complete drying;
  • self-leveling floor. The height of the screed floor 3-10 mm. Therefore it must be applied in several layers. Poured floor is recommended when installing electric floor heating under the laminate floor;
  • tile adhesive. Proven according to the reviews of users, which are advised to give preference, if electric under-tile floor heating is installed.

Regardless of the type of material used for screed, the optimal height (thickness) of the screed is 30-50 mm.

Surface preparation

Prior to the installation of a warm floor in the room should prepare the surface for the work. In some cases, you will even need to remove the old screed, if it is very damaged and has serious defects. It is removed to the base, to the floor slab, if possible. After that, all debris and dirt from the surface is removed.

If there are slight differences in height throughout the floor in the room, potholes, cracks, it is best to fill a small layer of rough cement-sand screed. You can proceed to further work only after the mortar dries out completely.

When everything is ready, the layer of waterproofing is performed. In addition to the floor base, the material must go to the wall, about 10-15 cm. Later on, the extra sections can be easily cut off with a construction knife. Do not forget about the damping tape (vertical waterproofing), which is necessary to suppress the thermal expansion of the screed during the operation of a warm electric floor.

Which one is better??

When choosing the type of screed must be guided by the type of subfloor, the purpose of the room and type of heating system. Concrete screed is suitable for all underfloor heating. The advantage of this screed is moisture resistance, durability and the ability to use in any type of premises. The concrete composition can be applied either on the existing subfloor, or on the ground. The disadvantages are the risk of cracking, delamination, and separation of the concrete floor from the substrate, as well as the need for regular wetting with water for up to 3 weeks until dry out. The final coating can be laid only after the full hardening of the screed.

Gypsum screed belongs to the semi-dry type because of the small amount of fluid required for preparation of the mortar. It is a self-leveling mix, which dries and hardens very quickly. The advantages of such a screed is the lack of necessity for laying reinforcement mesh and the preliminary surface priming. The layer of coating may be less than three centimeters. Due to the porous structure of the semi-dry screed provides high thermal and acoustic insulation of the room.

Self-leveling mixes are easy to prepare, environmentally friendly and have smooth and glossy surface after complete drying. Suitable for all kinds of underfloor heating. To improve plasticity and prevent cracking the dry mixes contain additives in the form of fiber and modifiers. The disadvantages include too rapid setting of the mortar.

As a result, the composition should be prepared in small portions that can be used within an hour.

Technology of filling screed with the installation of electric cable floor heating

Today, underfloor heating takes a strong position in the heating market for residential and commercial premises. The main advantage of this system of heating is that the heat is distributed evenly vertically (from the floor to the ceiling)

Photo with FH

Filmed floor heating. It is laid under the finish flooring, such as laminate, carpeting, linoleum. This type of floor heating is easy to install and has a minimum system thickness. This kind of flooring is not suitable if tiling or underfloor heating in wet rooms is intended, since the foil is not resistant to moisture, tile adhesive or sandcrete screed.

Important! When choosing a floor covering, please pay attention to its certification for use with underfloor heating.

Heating mats. Are firmly insulated and laid in a grid heating cable with a calculated pitch. Thermo mats are produced in defined widths and heating area multiples 0.5 m², 1 m², 2 m² etc.д. This type of floor heating is often applicable when there is no possibility to increase the floor height and pour a full screed, and mats are mounted directly into the tile adhesive layer (about 5 mm). The power of this heating system is calculated on the basis of the heat loss of the house that it must compensate for. For dry rooms, as an additional heating system, the wattage of the thermo mats is selected on the basis of 120. 140 W/m². For basic heating systems at least 150 W/m². For rooms with high humidity and non-insulated rooms. 180. 200 W/m².

Floor heating on the basis of heating (single-core or double-core) cable in a shielding braid, minimizing electromagnetic radiation. With this type of underfloor heating, the output of the system can be varied manually by adjusting the laying step on the installation tape. When installing the heating cable, it is laid in the screed of sand-concrete, which thickness is from 3 to 6 centimeters, which leads to a good heat accumulation in the room.

When choosing the type of floor heating, you must remember that the greater the thickness of the screed, the longer will be heating the floor and the room as a whole, but at the same time the floor will take longer to cool. After completing the installation of a warm floor based on heating mats, they can be used after 10-14 days, for the heating cable screed from sandcrete need time to gain strength, so the period before operation increases to 21-28 days.

Let’s consider in more detail one of the above-mentioned types of electric floor. a floor with a heating cable, laid in a screed of sandcrete. To make a reliable and durable floor screed from sandcrete and avoid mistakes when installing the heating system you need to know:

  • What is the correct “pie” of electric floor heating with heating cable.
  • What are the nuances of choosing high-quality cement and sandcrete, preparing the mixture and pouring screed.
  • What is fiber used for.
  • How to do the installation of floor heating with a heating cable when pouring a sand-concrete floor screed.

The “pyrolysis” of the floor heating with heating cable is selected taking into account the characteristics of the room, including its heat loss. To reduce the latter, it is necessary to insulate the base of the future floor heating. The correct “pie” of the floor heating is a guarantee that it will not have to heat the apartment above or the room below you, whether it is a living area or the basement / cellar, and not to increase costs in the operation of the floor heating system.

For substrate under the heating cable is used multifoil. a special material in which a layer of foil is protected by a layer of polyethylene from the negative effects of the alkaline environment of the concrete. Multifoil will prevent direct contact of the heating element with the insulation, as well as evenly distribute heat in the screed.

MIF. Often the use of foamed thermal insulation with a foil layer is used in the underfloor heating system. The myth of this action is that the foil layer will allegedly reflect the heat energy upwards. But in fact, the reflective effect of the foil does not work in solids (concrete screed). In addition, conventional foil dissolves in the alkaline environment of the concrete mortar or adhesive, and foamed insulation shrinks over time under the weight of the screed, which leads to cracks.

The scheme of the optimal “pie” of a warm floor with a heating cable is as follows:

  • On a flat and clean base is laid insulation. The best option for it is EPPS (extruded polystyrene foam), with a recommended thickness of 3-5 cm.
  • Along the perimeter of the walls of the room is mounted damping tape, which compensates for the thermal expansion of sand-concrete screed with a warm floor.
  • On top of the insulation is laid multifoilga or metal mesh, which also prevents the contact of the cable with the insulation. The size of a cell: 25×25 mm or 50×50 mm. Bar diameter 1.6-3 mm.
  • On top of the installation tape is rolled out, which is attached to the grid with plastic clamps. Heating cable is fixed on a mounting tape, keeping a step of laying in accordance with the area of a room and cable length. The average step for laying the heating cable is 10-12 cm. Plastic clamps can be used as cable fixers. Advice. To reinforce the metal mesh screed, being in the thickness of sand-concrete, but not under it, you need to raise it over a layer of insulation, using scaffolding or small pieces of EPPS. Another option is to lay a second layer of mesh over the cable.
  • After installing the heating cable and the temperature sensor, which should be in the “body” of the screed, the system is checked for visible damage to the cable and tested for proper functioning of the electrical part. Then you set the beacons and pour the screed with a thickness of 3 to 6 cm.

Important! Pour the screed correctly from the wall opposite the entrance. When leveling highly mobile or cast screeds it is impossible to use spiked rollers, in order to avoid damaging the heating cable.

Quality work on the screed directly affect the durability of the finished floor covering. On how to choose a quality screed can be found in the video.

For pouring the screed you can prepare a mixture based on cement and sand yourself, or use a ready-made dry mix. Sandcrete. The advantage of an already prepared mixture is clearly verified parameters on the crack resistance of the cured mortar, as well as the exact proportions of cement and sifted sand.

For screed on a warm floor is better suited to “wet” screed. The main difference between the “wet” screed from “semi-dry”. Semi-dry screed is difficult to qualitatively distribute and seal, taking into account the installed system of underfloor heating. With a decrease in the density of the cement stone, due to the formation of air cavities, reduces the efficiency of heating, as reduces the thermal conductivity of the screed.

When independently preparing sand-concrete for screed, special attention should be paid to the quality of ingredients. The sand should be coarse, sifted, without clay and other harmful impurities. When selecting the proportions of the mixture, remember that the sand can be different moisture, which affects the required amount of mixing water.

When working with ready-made dry mixes, be sure to follow the recommendations for basic formulations and the exact proportions of the preparation of basic types of mortars.

To improve the quality characteristics of sand concrete and screed, you can use plasticizers and fiber.

The amount of plasticizer is indicated on the packaging of the product and is calculated by the mass of cement, not the finished mortar. This reduces the amount of mixing water required, due to the fact that the additive has water-reducing properties. It also increases the workability and plasticity of sand-concrete. The mortar stretches well along the screed, is compacted and smoothed.

Reinforcing the screed with a metal mesh is applicable if its thickness is more than 5 centimeters. If the thickness of the cement screed is less than that, polypropylene mesh or polypropylene fiber is added to the mortar for reinforcement.

It is desirable to use fibrous screed mortars together with chemical admixtures. plasticizers. If you choose sand concrete for screed, the fiber is used in the following scheme:

  • Pour the dry mixture into the concrete mixer or a working tank.
  • Add a small amount of water (1/3 of the recommended amount) and mix thoroughly.
  • Gently moisten the fibre and gently add it to the mixture. Thoroughly stir the mixture with fiber, until the fiber is evenly distributed in the mortar. When mixing it should not form “urchins” from the fibers of the fiber.
  • Measure the amount of chemical plasticizer recommended by the manufacturer, mix it with 2/3 of mixing water, add the obtained to the mortar, while constant stirring.
  • After 1.For 5 to 2 minutes of mixing add additional water to achieve the desired mobility. Stir for another half minute.

Use of fiberglass reduces labor costs associated with the reinforcement of the screed with metallic mesh, increasing the quality of the screed, and reducing the likelihood of cracking.

The screed must be properly maintained after pouring. The freshly laid screed is covered with a polyethylene film and drafts in the room are excluded. Such manipulations will retain moisture and prevent it from evaporating quickly. To gain strength without internal stresses that can lead to cracks, the screed must be periodically moistened during the first week after pouring. Before the final surface finish of the floor the surface of the screed must be dusted and cleaned from contamination.

Installing the floor heating

How best to install electric floor heating depends on the type of heating elements. For any underfloor heating it is important to ensure that the heating elements do not touch the thermal insulation. To do this, they are separated from it with reinforcement mesh.

Installing the cable

Choosing the location of the thermal regulator. It is mounted at a height of more than 30 cm from the floor. If the device is a hidden type, you punch a hole in the wall for it, as well as for the wires of power and temperature sensor. Do not install thermostats in wet areas. They are carried into the adjacent rooms.

Mount the mounting tape on the base at intervals of 50-100 cm and with a margin of 30 cm from the walls. On the floor, a marking is made, taking into account the indentation from the furniture. The distance from the walls is 10 cm, and from pipes and radiators. 15 cm. Then the heating cable is connected to the power cable with a sleeve, and then. mounted on the installation tape.

The power cable is led through the groove made in the wall to the thermoregulator, and the heating cable is laid according to the scheme. At the same time the radius in the bends must not be less than 5 cm. Curves are made smoothly, without any unnecessary tension. Fixing is performed with staples or mounting tape. Do not touch or cross coils. The convergence should not be less than 8 cm. All indents are strictly observed according to the scheme, which is developed in advance.

Installing the cable floor heating with an indentation

The temperature sensor is placed inside the corrugated pipe freely, together with the supply leads. One end of the conduit is sealed with a stopper to prevent the cement mortar from getting inside. A pipe with a temperature sensor is placed between the coils of the cable at a distance of at least 50 cm from the wall and is laid in a prepared chink, and then the wires are connected to the thermostat.

After installation and wiring, check the electrical resistance of the heating cable and the sensor. It has to be at least 10 % different from the passport values.

Wall plugs are sealed with grout or filler, and after curing, the functionality of the underfloor heating system is tested.

Installing the heating mat

It is easier to install heating mats, because the cable is already fixed to a grid, which you just need to lay out on the ground. At the bends, the mesh is carefully cut without damaging the cable’s integrity. In places where there are obstacles, the mesh is removed and the cable is laid with the observance of the distance from neighboring coils within 6-8 cm.

Heating mat turning during installation

An important advantage of heating mats is their small thickness, which makes it possible to pour a thin screed or to install heating elements in a layer of tile adhesive. Then the thickness of the fill will be only 8-10 cm, which will not take up unnecessary volume of the room.

Installation of the rod floor

Rod infrared heaters look like a rope ladder. They contain transversal heaters and 2 longitudinal connecting wires, which supply power.

The core roll is rolled out on the floor, starting from the thermal controller. At the turning points, the connection wire is cut and then the ends are reconnected with a piece of wire. This reduces the reliability of the floor heating. It is advisable to choose rolls of a suitable length. Then you don’t have to cut anything.

After laying in the insulation windows are cut out in a staggered manner for better adhesion of screed to the base. All connections must be carefully insulated.

Installing the components of the floor heating

To ensure that the floor heating system is fully functional, before pouring the concrete screed, the attachment points for the main sensors and components must be determined. Install the thermostat on the wall surface and, if possible, close to an existing socket. The distance from the floor should be at least 30 cm, as the temperature from the base will somewhat distort the information transmitted.

The temperature sensor is placed into the floor subfloor, which will later be filled with the prepared mortar. It is worth noting here the point that in direct contact with the mortar, it may fail. To avoid this, the temperature sensor is placed in a corrugated pipe that leads from the temperature controller on the wall. All open sections of the corrugation are sealed with sealant, so that no mortar gets into them during the pouring. It is not superfluous to additionally install a special plug at the end of the tube in the base.

Heating elements are laid on the basis of the outlined scheme, which will also display the step of their laying. Do not deviate from the drawing, as it is previously calculated all the details. After completing the work with the components of the floor heating, you need to test their performance, connecting them to the mains. Measured the resistance of the cable, which should correspond to those data that are prescribed in the passport for it. If the result is positive, you can proceed directly to the pouring of concrete mortar.

The function of the screed is to increase the efficiency of the floor heating system and protect the cable from mechanical damage.

Features of the screed are as follows:

  • Reinforcement is necessary. Any other option is doomed in advance to cracking and remodeling. Therefore, it is worth accepting the fact that it is necessary to perform a reinforced concrete pipe.
  • Waterproofing and insulation is necessary.
  • The thickness of the screed depends on the selected cable and is chosen according to special tables or in accordance with the heating cable certificate according to the manufacturer’s recommendations.
  • In large rooms, to avoid cracking even the reinforced concrete, provide temperature joints, which will compensate for the thermal expansion of concrete.
laying, floor, heating, cable, screed

Electric underfloor heating: cost, characteristics, advantages and installation technology

Electric underfloor heating is a system mounted directly into a cement-sand screed, designed for additional heating of any type of premises: from a bathroom, and ending with a living room, bedroom or kitchen.

Thanks to the ease of installation, the affordable price for the floor heating, high security and reliability, these systems are often used as an auxiliary source of heating in cottages, eco-houses or townhouses.



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